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Benefits and risks of episiotomy: A review of the English-language literature since 1980
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This is the manuscript which was later published as: --------------------------------------------------------------------------------

-- -------------------------------------------------------------------------------- Woolley RJ. Benefits and risks of episiotomy: A review of the English-language literature since 1980. Part I. Obstet Gynecol Survey 1995; 50:806-820 and
Woolley RJ. Benefits and risks of episiotomy: A review of the English-language literature since 1980. Part II. Obstet Gynecol Survey 1995; 50:821-835. Because some changes in wording and formatting were made in the editorial process, the final print version should be consulted for any quotations to be cited elsewhere.
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Robert J. Woolley, MD -------------------------------------------------------------------------------- Boynton Health Service -------------------------------------------------------------------------------- University of Minnesota
February 19, 1995
Office phone: (612) 625-8400 Office address: 410 Church St. SE, Minneapolis, MN 55455
E-mail: wooll005@gold.tc.umn.edu
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Abstract -------------------------------------------------------------------------------- The professional literature on the benefits and risks of episiotomy was -------------------------------------------------------------------------------- last reviewed critically in 1983, encompassing material published through 1980. The purpose of this paper is to review the evidence accumulated since then. It is concluded that episiotomies prevent anterior perineal lacerations (which carry minimal morbidity), but fail to accomplish any of the other maternal or fetal benefits traditionally ascribed, including prevention of perineal damage and its sequelae, prevention of pelvic floor relaxation and its sequelae, and protection of the newborn from either intracranial hemorrhage or intrapartum asphyxia. In the process of affording this one small advantage, the incision substantially increases maternal blood loss, the average depth of posterior perineal injury, the risk of anal sphincter damage and its attendant long-term morbidity (at least for midline episiotomy), the risk of improper perineal wound healing, and the amount of pain in the first several postpartum days.
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Outline -------------------------------------------------------------------------------- Introduction -------------------------------------------------------------------------------- Benefits Prevention of lacerations Prevention of third- and fourth-degree lacerations Longitudinal changes in practice Laceration rates with and without episiotomy. Comparisons between birth facilities. Comparisons between delivery attendants. Case-control study. Serial observations. Statistically adjusted serial observations. Randomized controlled trials. Operative vaginal deliveries. Summary. Episiotomy versus spontaneous tear Pain during delivery. Postpartum pain. Long-term pain. Dyspareunia. Healing problems. Wound infection. Edema and hematoma. Ease of repair. Long-term morbidity. Frequency of perineal damage. Summary. Prevention of anterior lacerations Summary Prevention of pelvic relaxation Symptomatic urinary incontinence Pelvic floor muscle strength Summary Prevention of fetal injury Intracranial hemorrhage Intrapartum asphyxia Fetal distress Shoulder dystocia Summary Risks Blood loss Morbidity of anal sphincter damage Psychosocial consequences Miscellaneous risks Fetal risks Maternal risks Risks to birth attendants Summary Conclusion References Tables
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Introduction -------------------------------------------------------------------------------- In 1983, Thacker and Banta published a comprehensive review of the -------------------------------------------------------------------------------- English-language literature to 1980 on the benefits and risks of episiotomy [1]. (Shorter versions of this paper were published in 1982 [2-3].) After examining the available evidence on the claimed benefits of episiotomy — prevention of third-degree laceration, damage to the pelvic floor, and fetal injury (mechanical and hypoxic) — they concluded that "little research has been done to test for benefit of the procedure, and no published study can be considered adequate in its design and execution to determine whether hypothesized benefits do in fact result." Conversely, these authors found that the risks of episiotomy — extension, unsatisfactory anatomic results, blood loss, pain, edema, and infection — were "more severe than many might appreciate."
Thacker and Banta's seminal review has had a profound effect. The pace of research on episiotomy has increased dramatically since its publication, and the quality of much of this data exceeds anything available in 1980.
The purpose of this paper is to review the English-language literature on the benefits and risks of episiotomy published since 1980.
Material for review was located through a manual search of Index Medicus and a computerized search of a MEDLARS-derived CD-ROM database (Ovid 3.0, CD PLUS Technologies), for all English-language articles indexed with the subject heading or abstract text word "episiotomy" through October, 1994, with a publication date of 1981 or later. The same software and parameters were also used to search the Nursing and Allied Health (CINAHL) and Health Planning and Administration (HEALTH) databases. Several prominent obstetric textbooks were also consulted for their relevant references. All of these primary sources were then reviewed for further references meeting the same restrictions, and this process repeated iteratively. Eight potentially applicable items (papers in non-indexed journals, books, and book chapters) identified by this procedure could not be located. At each stage, some papers were obviously not pertinent to a discussion of the benefits and risks of episiotomy (e.g., studies of post-episiotomy pain relief methods), and were not obtained. Others, after review, could be seen not to pertain to the subject matter (e.g., instructional articles in midwifery journals, or studies in which episiotomy was an outcome variable rather than a study variable); these are not referenced herein. Where details of methodology are not critical to the value of a paper (e.g., case reports), foreign-language articles with electronically accessible English abstracts were also included. Although Thacker and Banta's review [1] ostensibly ended with 1980 publications, they actually included a few papers dated 1981 and 1982; these are therefore not given further attention here.
Benefits The trouble with people is not that they don't know but that they know so much that ain't so.
- Josh Billings
Prevention of lacerations Current American obstetric texts continue to assert that episiotomy "prevents perineal lacerations" [4]. Alternatively, some claim that "an episiotomy is generally preferable" to a spontaneous laceration [5] because "it is easier to repair" [6]. (Until the 1993 edition of Williams Obstetrics, it continued to maintain that an episiotomy would cause less pain and heal better than a spontaneous tear.) I will examine each of three specific claims in turn: 1. episiotomy reduces the incidence of third- and fourth-degree lacerations; 2. episiotomy is preferable to a spontaneous perineal laceration; 3. episiotomy reduces the incidence of anterior perineal lacerations.
Prevention of third- and fourth-degree lacerations It is almost universally accepted that rupture of the anal sphincter (third-degree tear), especially with concomitant disruption of the rectal mucosa (fourth-degree tear), is the common complication of highest morbidity from either a spontaneous laceration or from extension of an episiotomy. (Although the presence of rectal mucosal involvement probably carries risks — such as rectovaginal fistula — distinct from isolated sphincter damage, in this paper the term "third-degree" will be used to include both categories of injury, since much of the research on the issue considers them together.) More modern research has focused on the relative frequency of third-degree perineal injury, with or without episiotomy, than on any other aspect of the debate on the use of the procedure. Does either mediolateral or midline episiotomy reduce the patient's risk of suffering anal sphincter damage? Several distinct lines of evidence have been used to address this question.
Longitudinal changes in practice. The most indirect type of data bearing on this question is the observation of trends over time. In France between 1972 and 1981 the episiotomy rate (mostly mediolateral) rose from 8.1% to 32.1%, without significantly changing the rate of third-degree tears (0.7% in 1972, 0.6% in 1981) [7]. Conversely, Reynolds and Yudkin documented a rapidly decreasing use of mediolateral episiotomy at a large British hospital from 1980 to 1984 [8-9]. While the rate fell from 72.6% to 44.9% among nulliparas and from 36.8% to 15.4% among parous women, there was no significant change in the incidence of anal sphincter damage.
Röckner observed a decline in episiotomies (mostly mediolateral) among nulliparas within her hospital from 49.9% in 1984 [10] to 33.6% in 1988-1989 [11]. The risk of third-degree tears actually fell over the same period from 3.3% to less than one percent, while the chance of delivery with an intact perineum rose from 28% to 44%.
Perhaps as a result of their investigation into the postpartum effects of episiotomies (discussed in a later section of this review), Larsson et al incidentally noted a subsequent decline in the rate of mediolateral episiotomy at their Swedish hospital from 28% in 1984 to "less than" ten percent in 1988 [12]. Over the same period the anal sphincter rupture incidence fell from 1.6% to 1.1%, not a statistically significant change.
An interesting variation on this type of data is the report of Legino et al [13]. They published the rate of third-degree lacerations in one hospital for every fifth year from 1935 to 1985. From 1935 to 1965 the rate was always less than one percent. Starting with the 1970 numbers, the rate never fell below 4%, reached 20% in 1980, and has stabilized at around 17%. Of course, nearly every aspect of obstetric care changed gradually over that 50 years, but the sudden and dramatic change in severe laceration rate is most likely attributable to a hospital policy change between 1965 and 1970 which "required that midline episiotomies replace mediolateral ones." Obviously this speaks not to the effect of episiotomy per se, but to the type of incision used.
Laceration rates with and without episiotomy. A second line of evidence is simple tabulation of laceration rates with and without episiotomy. Thacker and Banta [1] cited seven papers published between 1919 and 1981 that variously gave the rate of spontaneous third-degree laceration (without episiotomy) as 0-6.4%. In the same period, six studies found a range of 0-9.0% for extension of mediolateral episiotomies, and 15 studies reported the rate for midline episiotomies as 0.2-13.5%, with one outlier at 23.9%. Table 1 presents the comparable raw data from subsequent research. Such simple comparisons of laceration rates, while interesting, are fraught with interpretive peril. The studies cited vary enormously in every potential confounding factor. Furthermore, the quality of the data in Table 1 varies widely, from almost casual observations of small numbers of patients by one practitioner to sophisticated randomized trials. (Many of these will be discussed in more detail elsewhere in this review.) Finally, the operators might be able to predict which patients will suffer a spontaneous third-degree tear; an episiotomy under such circumstances could theoretically reduce a patient's risk of sphincter damage, though it shifts those high-risk patients to the episiotomy column.
Comparisons between birth facilities. A third type of observational study is a comparison of episiotomy and laceration rates between groups of patients cared for concurrently at two or more institutions. Röckner and Ölund studied a random sample of delivery records of 400 women from two hospitals in the same county in Sweden, one a referral university hospital, the other a community hospital which refers anticipated complications to the university hospital [11]. The university hospital performed episiotomies in 26% and the community hospital in 35% of their nulliparous patients. (Over 90% of episiotomies in both facilities were mediolateral.) Comparing women either with or without an episiotomy, the rates of anal sphincter damage were not significantly different between the hospitals.
Comparison between a free-standing New York City "childbearing center" and large teaching hospital was made by Feldman and Hurst [14]. The 149 patients were demographically similar. Predictably, nearly every intrapartum intervention was used more frequently at the hospital, including episiotomy (78.1% versus 47.2%). The third-degree laceration rates, however, were nearly identical (9.5% and 9.7%).
A series of three articles [15-17] reported on a Philadelphia university hospital and a nearby maternity hospital, where care is provided primarily by midwives. Study samples were randomly selected from birth records so that patients were matched for race, age, education, previous birth outcome, and parity (52% nulliparous). In order to reduce the effect of referral bias, which could not be eliminated from either of the studies previously discussed, subjects were excluded if they were referred from the maternity center or carried a diagnosis that would have required such referral. Furthermore, the analysis was stratified by prenatal and intrapartum risk score. As noted by Feldman and Hurst, essentially every obstetric intervention measured was used more frequently at the university hospital. Episiotomy use, specifically, was 64.8% versus 43.1% at the maternity center, while crude third-degree laceration rates were similar. After adjustment for seven variables associated with episiotomy rate, logistic regression revealed the use of episiotomy to be the most significant risk factor for development of a severe tear (adjusted odds ratio 4.3); nulliparity was a distant second, with an odds ratio of 1.5. This analysis was performed with mediolateral and midline episiotomies combined. Unfortunately, the authors do not tell us the proportions of these two types, but they assert that the results did not change when analyzed for either one alone.
Comparisons between delivery attendants. Six studies have compared groups of patients within the same hospital cared for by practitioners with different episiotomy rates. The smallest study of this type was carried out by Mayes et al [18] at the University of Michigan Hospital. They compared 29 consecutive deliveries on the nurse-midwifery service with 29 delivered by physicians in the same hospital. The patients were matched for age, parity, and infant birth weight. The midwives used midline episiotomy in 24% of births, the physicians in 76%. The respective rectal injury rates, all of which occurred as episiotomy extensions, were 6.9% and 20.7%. These patient groups differed in employment and marital status, as well as in use of several labor interventions (delivery room, oxytocin, amniotomy, monitoring, and analgesics), precluding causal inference.
In Denmark, Henriksen et al retrospectively grouped 2188 patients according to the overall episiotomy rate of the midwife to whom they were arbitrarily assigned upon admission [19]. Group 1 patients were delivered by midwives with an episiotomy rate of 7.2-32.8%; group 2, 34.2-47.4%; group 3, 48.5-73.8%. (It is not clear whether these midwives' practices were determined before or during the study period.) Patients were well matched between groups on all measured characteristics including nulliparity (43.1% overall). All episiotomies were mediolateral. The three groups experienced anal sphincter tears at respective frequencies of 1.2%, 2.2%, and 2.0%, not a significant difference. Women in group 1 were significantly more likely to have an intact perineum postpartum than group 3 (37.5% versus 25.5%). Ironically, the indication accounting for the majority of excess episiotomies in groups 2 and 3, reported by the attending midwife immediately after delivery, was prophylaxis against a perineal tear.
Several years earlier and about 150 kilometers away, a smaller study of comparable design was carried out by Thranov et al [20]. This one suffered from being dependent on the patients' return of a postal questionnaire rather than including records from all patients meeting the research criteria. However, response rates were uniformly high across groups of patients divided on the basis of the episiotomy rate (determined in advance of the study period) of the midwife to whom they were arbitrarily assigned at admission. These rates were grouped essentially as in the study by Henriksen et al. Also as in that work, there was no difference found between the patients in the three groups in terms of maternal age, length of second stage, or infant birth weight. The three groups' mean episiotomy rates (all mediolateral) were 21%, 34%, and 70%, while the corresponding frequencies of complete perineal tears were 2.4%, 1.6%, and 0%, not a significant difference.
A group of obstetric residents in North Carolina used a different approach [21]. One resident was selected to use episiotomy only for fetal distress or operative vaginal delivery, while his colleagues continued their use of episiotomy (all midline) at their own discretion. Patients were not randomized to attendants, and no information was given as to how patients were allocated among the residents, but they were shown to be similar in birth weight, nulliparity, race, prematurity, operative vaginal delivery frequency, and incidence of low Apgar scores. The restricted use of episiotomy was associated with a lower risk of third-degree perineal laceration, 1.8% versus 13.2%; when subjects were subdivided by parity, this difference remained significant among nulliparous, but not parous, women, though a similar trend was apparent even in the latter. Interestingly, no patient in either management protocol experienced a severe tear without a preceding midline episiotomy.
Chambliss et al prospectively randomized patients to management by either the obstetric residents' service or the midwives' service within the same California hospital [22]. The participants continued their usual care without restriction. The primary intent of the study was to determine whether the previously observed discrepancy in cesarean section use between the two services was due to differences in case mix or differences in management styles; perineal damage was a secondary outcome variable. Presented with an essentially identical patient population, the midwives had a significantly lower rate of episiotomy (10.8%) than the residents (35.4%). When an episiotomy (mediolateral versus midline not reported) was performed, the midwives also had a lower likelihood of rectal extension (8% versus 22%), indicating a difference between the practitioners in the nature of the incision, other related management variables (such as the observed variance in operative vaginal deliveries), or both. Unfortunately, the authors did not clearly say whether any severe spontaneous lacerations occurred, so the overall rate of sphincter damage cannot be compared. They did, however, conclude that "our study suggests that episiotomy may be associated with more perineal trauma."
In a randomized controlled trial (about which more later), Klein et al demonstrated that the physicians with the highest usage of midline episiotomy accounted for a disproportionately large share of the third-degree tears and a disproportionately small share of the intact perinea among nulliparous women [23]. Those with the lowest episiotomy rates had opposite results. The difference was dramatic, with highest-users having a third-degree tear rate of 20.9% versus 1.9% in the lowest-use group.
Finally, Flint et al randomized patients to routine prenatal and intrapartum care — usually including delivery by a "junior doctor" — or to a concerted effort for continuity of care with a small team of midwives [24-25]. The attendants' episiotomy rates proved too similar (42.2% and 34.3%, respectively) to allow conclusions about the resultant rates of third-degree tears (0% and 0.5%).
Case-control study. When an outcome is uncommon, a retrospective case-control design is appropriate to identify risk factors found more often in cases than in matched controls lacking the outcome in question. Like the other types of observational studies discussed in this section, case-control design cannot prove causality. Only one case-control investigation has been done to determine risk factors for anal sphincter tear during vaginal delivery [26]. Møller Bek et al reviewed all births from 1976 to 1987 at the Aarhus University Hospital (Denmark). Among 42,000 deliveries, 152 cases of third-degree laceration occurred. These patients were compared to a group consisting of the women delivering immediately before and after each index case. As might be expected, the groups differed in several preexisting characteristics and in several aspects of labor management: cases had a lower average age, lower parity, higher birth weight, more abnormal presentations, more shoulder dystocia, longer second stage, and more interventions (oxytocin, instrumental deliveries, and episiotomies). Because many of these factors were understandably thought to be associated with each other (and therefore not all independent risk factors for severe tear), a multiple logistic regression was performed. After adjustment for the effect of the other variables in the model, mediolateral episiotomy remained the third most powerful predictor of anal sphincter damage (adjusted odds ratio 2.8), after shoulder dystocia (adjusted odds ratio 58.9) and forceps delivery (adjusted odds ratio 4.4).
While not following strict case-control design, Crawford et al collected similar data incidental to their study of symptoms resulting from anal sphincter rupture [27]. The records of an arbitrary (not random) sample of 35 Michigan women with and without this complication following delivery were reviewed. Both forceps and episiotomy were used more frequently in cases than controls (odds ratios 22.7 and 4.89, respectively). No statistical adjustment was made for interactions among preexisting and intrapartum risk factors.
Serial observations. The most straightforward and common type of report on the relationship between episiotomy and third-degree lacerations is simple compilation of birth records at one or more facilities. Many such studies are very small and/or report episiotomy and laceration data incidental to some other primary research objective (such as postpartum pain) [28-33]. The data from these are included in Table 1, and they will not be discussed in more detail. An archetypal paper of this design is a study of 807 consecutive nulliparas delivering in a university hospital near Stockholm in 1984 [10]. Patients receiving an episiotomy (almost all mediolateral) had a 4.2% chance of a third-degree laceration, compared to 1.7% with no episiotomy. Overall, 50% of patients had an episiotomy; fetal distress was a main or contributing indication in 80% of these. (It is difficult to believe that 40% of all primiparas are experiencing true fetal distress, but that is what the participating midwives reported.) This paper also illustrates the limitations of the unsophisticated study design. The patients receiving episiotomy differed from the others in nationality mix, use of oxytocin, duration of first and second stages of labor, type of anesthesia used, frequency of operative delivery, and probably in several other unreported parameters.
Some papers do not even report this information in a format that allows the reader to determine that confounding factors exist. Rooks et al describe 11,814 births occurring in U.S. birth centers, mostly delivered by nurse midwives [34]. Although data were available to control or adjust for multiple potential confounding variables, only operative delivery, birth weight, and delivery position were presented in strata.
Pearl et al reported on 564 San Francisco births of infants in the occiput posterior position [35]. Among the spontaneous deliveries, third-degree tears were suffered by 6% without episiotomy, 11% with mediolateral episiotomy, and 20% with midline episiotomy ( Table 1). Again, results are confounded by length of the second stage, presence of fetal distress, and occurrence of shoulder dystocia. No information on parity is given.
The relationship between episiotomy and anal sphincter damage is therefore difficult to interpret causally in these studies. The papers reviewed in the next section all attempt to make some adjustment for such confounding variables.
Statistically adjusted serial observations. In 1985, Buekens et al published their analysis of 21,278 deliveries occurring between 1974 and 1978 at ten Belgian hospitals [36]. Mediolateral incision was performed in 28.4 % of all patients. Third-degree tears occurred in 1.4% of patients with episiotomies and 0.9% of patients without. Although this was a highly significant difference in a population so large, the results were complicated by the fact that episiotomies were performed more often in primiparas, with breech or occiput posterior presentation, and with instrumental deliveries, all of which might increase the risk of sphincter damage independently of the episiotomy. The authors therefore restricted their analysis to patients with spontaneous, vertex, occiput anterior deliveries. To help correct for the confounding effects of parity and birth weight, data were stratified into three weight groups and analyzed separately for nulliparous and parous women. The episiotomy and laceration rates are shown in Table 1 (without the birth weight stratification). Calculated in this way, no positive or negative influence of episiotomy remained. Buekens et al reported that their statistical analysis also included "other methods to control confounding including log-linear modeling. These methods gave identical results." No details of these "other methods" were published. At the University of Cincinnati, Gass et al attempted to reduce the influence of confounding variables by eliminating operative vaginal deliveries and retrospectively matching 205 pairs of patients with and without a midline episiotomy on the basis of age, parity, and infant's birth weight [37]. Their results are shown in Table 1. Not only was anal sphincter damage significantly more common in the patients with episiotomies, but, as observed by Mayes et al [18] and Thorp et al [21], no deep laceration occurred without a preceding midline episiotomy.
Borgatta et al noticed a dramatic difference in laceration rates among 241 nulliparous women undergoing spontaneous vaginal deliveries in New York City, depending on whether a midline episiotomy was performed (see Table 1), with an estimated odds ratio of 22.5 [38]. No confounding effect was seen for maternal age, Apgar score, or delivery attendant (obstetrician or midwife). However, delivery position (a factor rarely reported by others) also exerted a strong independent effect on risk of sphincter damage, with an odds ratio of 14 for use of stirrups versus all "legs unrestrained" positions. Use of an episiotomy in a patient in stirrups almost doubled her risk of deep laceration from what it would have been with just one of these interventions.
Three North American papers have used statistical modeling to estimate retrospectively, in the presence of multiple confounding variables, the strength of episiotomy as an independent risk factor for severe lacerations.
Walker et al reviewed all deliveries at their Toronto hospital for three years [39]. They found 8994 patients with term, spontaneous, vertex deliveries, normal labor progress, and no fetal distress (another factor not usually accounted for in other reports). They searched for statistical interrelationships between parity, episiotomy, epidural anesthesia, forceps, and perineal damage. Episiotomy, considered alone, increased the risk of a major laceration four-fold; this effect held for both mediolateral and midline episiotomies. Although parity and the use of forceps exerted lesser independent effects, no positive or negative interaction was found between these variables and the use of episiotomy.
In a study of 2706 San Francisco women, Green and Soohoo reported, among a large number of recorded variables, six that initially appeared to have an independent effect on the risk of third-degree tear: midline episiotomy, parity, accoucheur (physician or midwife), use of a delivery room (versus a labor bed), infant birth weight, and maternal race [40]. Factors not independently associated with a rectal injury included the type of anesthesia, maternal age, and length of second stage of labor. Of these, use of episiotomy was the strongest predictor, with a univariate odds ratio of 17.7. Further analysis corrected for interactions between variables; episiotomy remained the most important risk factor, with an adjusted odds ratio of 8.9. (Nulliparity was a distant second, odds ratio 3.3.)
The last of the observational studies to be considered here is that of Shiono et al [41]. Using data from the well-known Collaborative Perinatal Project, they identified 24,114 singleton, vertex deliveries of infants over 500 grams. The raw data showed mediolateral episiotomy to have an overall odds ratio of 8.3 for a third-degree laceration (1.2 and 5.3 for nulliparous and parous women, respectively); that for midline episiotomy was 49.7 (12.5 and 32.3, respectively). After adjusting for multiple confounding variables (presentation, pelvic dimensions, use of forceps, birth weight, and maternal age, race, height, and weight), midline episiotomy remained the most important risk factor for severe perineal damage for both nulliparas and paras (odds ratios 4.2 and 12.8, respectively). Mediolateral episiotomy was associated with a reduced risk (odds ratio 0.4) among nulliparous women, the only time such a protective effect has been identified since 1980. An insignificantly increased risk (odds ratio 2.4) remained for mediolateral episiotomy in parous patients.
The deliveries analyzed by Shiono et al [41] occurred earlier (1959-1966) than those in any other study under consideration here. It is possible that some of the episiotomies were performed in a way that differs from modern obstetric practice (for example, earlier in second stage). The authors themselves note that the incidence of cesarean section has risen conspicuously since the study period; undoubtedly, some of their observed patients would now be delivered abdominally. This limits to some degree the direct applicability of the results to current patient care. Nevertheless, there is no compelling reason to discount the general direction of the effects found.
Randomized controlled trials. No amount of statistical manipulation can correct for unrecognized risk factors, which may lurk anywhere [42]. In the investigation of the clinical relationship between an input variable (in this case, episiotomy) and an outcome (third-degree tear), the best way to minimize the influence of extraneous factors is with a randomized controlled trial (RCT). The goal is to achieve groups of patients comparable in every preexisting and management variable except the one in question. Five RCTs on the subject of episiotomy have been performed. Their results are shown in summary form in Table 2. The first RCT published was that of Harrison et al from Dublin [43]. They randomized 181 nulliparous women either to receive a mediolateral episiotomy or not to receive one unless "it was considered medically essential by the midwife or obstetrician in charge." Their participating attendants showed remarkable restraint in management of the latter group; only eight percent were deemed to require the incision, for instrumental delivery, fetal distress, prolonged second stage, or breech delivery. (The hospital's previous rate among nulliparas was 89%.) None of these had extensions; in the episiotomy group six percent did. The authors note that "None of the patients delivering without having had an episiotomy during either the study or the preceding six months sustained a third degree tear."
This study had several weaknesses. First, it did not provide information on when or how the randomization was performed, or data showing the resultant groups to be comparable. Improper randomization schemes have been the undoing of several RCTs [44-46]. Second, the authors did not perform a power analysis to determine whether a real effect (positive or negative) of episiotomy, if present, was likely to be found. Third, the study was primarily intended to investigate postpartum symptoms, not the occurrence of lacerations. Finally, much of the comparative data on such symptoms was reported by subsets of the allocation groups selected by outcome, rather than on an "intention to treat" basis.
Another RCT was carried out simultaneously in southern England [47]. Sleep et al randomized 1000 women delivering at a Reading hospital, where obstetric care is primarily provided by midwives, to a liberal or restrictive episiotomy policy (all mediolateral). In the former group the attendants' instructions were not necessarily to perform an episiotomy, as in the previous report, but to "try to prevent a tear"; this group had a 51% episiotomy rate, compared to 61% recorded in the hospital before the trial. The directions for the latter group were to "try to avoid episiotomy," with fetal distress the only acceptable indication; this resulted in a 10% episiotomy rate, about one-third of which were for maternal indications, contrary to the instructions. In the liberal policy arm no cases of anal sphincter damage occurred; two did in the restrictive use group. (The published data do not reflect whether either of these women had received an episiotomy.) The difference was not significant.
The smallest RCT yet published was carried out in London by House et al [48]. For their liberal use group, episiotomy could be performed at the discretion of the attending midwife. In the restrictive use arm, the only indication disallowed was prevention of laceration. House et al found too few third-degree tears to draw any conclusions about episiotomy as a protective or causative factor (Table 2).
Regrettably, the design of this trial incorporated a nearly fatal flaw. Patients randomized and observed through delivery were later excluded from all analyses if follow-up at three days postpartum could not be accomplished, and no arrangements for this third-day contact were made for the many patients who were discharged earlier than this. Because these were undoubtedly the ones who had the best outcomes, it is a distinctly non-random, post-hoc exclusion of a large (but unquantified) fraction of the enrollees. It was erroneous of the authors to exclude the patients from their analysis of the available data (especially information on lacerations).
Compounding the error, the results given in tabular form do not precisely match those in the text, and, for reasons not specified by the authors, it appears that some, but not all, forceps deliveries were excluded from their analysis despite complete data collection. Finally, the paper gives none of the data they claim to have collected on dyspareunia, pelvic organ prolapse, and stress incontinence. Because of these problems, and the small number of patients actually included in the published report (167), the conclusions of House et al cited throughout this review are much weaker than those of any of the other RCTs.
The largest and most recent of the five RCTs also involved mediolateral episiotomy exclusively [49]. Nulliparas and primiparas giving birth in eight Argentinean hospitals were randomized either to receive an episiotomy (83% actually did), or not to have one unless indicated by the status of the fetus (39% did); the reasons for violating the protocols in either direction were not enumerated. There was no significant difference in third-degree lacerations between the trial arms, either for nulliparous or for primiparous women.
The only RCT involving midline episiotomies is also the most methodologically rigorous episiotomy study design to date [50]. Klein et al studied 703 low-risk women of parity 0, 1, or 2 delivering at three Montreal university hospitals. Late in second stage they were randomized to a liberal episiotomy policy ("try to avoid a tear") or a restrictive policy ("try to avoid an episiotomy"). In the latter group, episiotomy was to be used only for fetal distress or if a "severe tear" was anticipated. No significant difference in sphincter damage was seen either for nulliparas or paras. Reminiscent of the findings of Thorp et al [21], Mayes et al [18], and Gass et al [37], this research found that 52 out of 53 severe perineal injuries were episiotomy extensions, and only one a spontaneous tear.
The chief limitation of Klein et al's study [50], as recognized by the authors themselves and a subsequent editorial [51], was the obvious reluctance of some of its participants to forgo episiotomy for the patients in the restrictive policy group. Their relative decrease in use compared to the control arm was about one-third, less than in any other RCT. The reasons given for performing an episiotomy contrary to instructions were severe tear anticipated (40%), fetal distress (29%), and perineum not distending (23%). Therefore, more than 60% of these procedures were for maternal indications.
In the conduct of such a trial, ethics obviously requires the allowance of episiotomy contrary to assignment in the case of true fetal distress. As a practical matter, there will be additional cases of episiotomy for questionable fetal distress, due to the high incidence and low specificity of fetal heart rate pattern changes late in the second stage of labor [52-57]; the number of such instances will depend on the personal intervention thresholds of the birth attendants. But the number of episiotomies performed for maternal indications should be few or none, and participants should be required explicitly to agree to these conditions.
In the absence of such compliance, a proponent of episiotomy could continue to argue that clinicians are able to predict which patients are about to experience a severe tear, and avert it with an episiotomy. Realistically, no one has yet demonstrated his ability accurately to predict this outcome. The folly of such predictions is suggested by comparing the high number of cases in which Klein et al's participants thought a severe tear was imminent, and the low number of actual tears seen when operators assiduously avoid this intervention, as in the RCTs by Harrison et al [43] and Sleep et al [47].
In spite of this limitation, the authors have recently strengthened the inference of a causal relationship between midline episiotomy and anal sphincter damage by re-analyzing their data according to perineal management actually received, rather than allocation group [23]. "When trial arm (protocol), age, hospital, oxytocin induction, oxytocin augmentation, epidural anesthesia, length of the first and second stages of labor, birth weight, and maternal position at birth were entered into the regression model — and thus controlled — the odds ratio for primiparous women experiencing spontaneous birth of sustaining a third- to fourth-degree tear in the presence of episiotomy compared with those not receiving episiotomy was +22.08 (95% confidence interval 2.84 to 171.53)."
Operative vaginal deliveries. An anonymous 1985 editorial in the Lancet opined that "Only an armchair accoucheur might cavil with [the use of episiotomy] in operative deliveries" [58]. Modern obstetric textbooks continue to prescribe the routine use of episiotomy with forceps and/or vacuum extractors [6, 59-60]. In spite of such dogmatic assertions, two groups have ventured to investigate the question of whether episiotomy increases or decreases the risk of third-degree lacerations in operative deliveries. Combs et al reported on 2832 consecutive operative vaginal deliveries (term, with vertex presentation) between 1975 and 1988 at a San Francisco teaching hospital [61]. Multiple logistic regression was used to control for eight factors other than episiotomy that could confound the relationship sought. The resultant model showed the use of midline episiotomy (versus mediolateral or none) to be the strongest predictor of anal sphincter damage (adjusted odds ratio 7.8), followed by nulliparity (3.6), forceps (versus vacuum; 1.9), and five other weakly predictive variables. In a separate univariate analysis, mediolateral episiotomy appeared to reduce the risk of deep lacerations during operative vaginal delivery, but the small number of cases (five) precluded adjustment for other factors or definitive conclusions.
A similar records review was performed by Helwig et al in North Carolina [62]. They identified 392 successful operative vaginal deliveries in 1989 and 1990 that met their criteria: singleton, vertex, with either midline or no episiotomy. (It is striking that 60% of their operative deliveries did not use episiotomies.) To identify risk factors for third-degree lacerations, they performed univariate analysis on the use of episiotomy and 14 other variables; unlike Combs et al [61], these investigators included several fetal variables — birth weight, fetal distress, meconium, and shoulder dystocia. Of all these, only episiotomy, birth weight, and parity proved significant. The data were then stratified by parity and birth weight. The risk of third-degree laceration was greater with episiotomy than without in each of the four subgroups created by this stratification. The final overall estimate was a 2.4-fold increased risk of anal sphincter damage when episiotomy was performed. (Table 1 shows the data, absent birth weight stratification.)
Relevant information was also contributed incidentally by Yancey et al, who conducted an RCT of prophylactic outlet forceps [63]. Of many variables considered in a logistic regression analysis, only the use of forceps and use of episiotomy (presumably midline) were significant risk factors for third-degree lacerations.
Finally, Pearl et al's study of occiput posterior deliveries found that among the operative deliveries, an identical 47.1% of those with no episiotomy and with midline episiotomy suffered third-degree tears, while only 13% of those with mediolateral episiotomy did [35]. While it is tempting to see this as a protective effect of mediolateral episiotomy, as the authors did, such a conclusion is poorly-founded, for the reasons given in section f. above.
Summary. Twelve years later, it is still the case, as concluded by Thacker and Banta [1], that no research of adequate quality has shown that episiotomy reduces a patient's risk of third-degree lacerations. This is true for mediolateral as well as for midline incision, for both nulliparous and parous women, and for operative and spontaneous vaginal deliveries. The only exception to this conclusion is the finding of Shiono et al of an apparent protective effect of mediolateral episiotomy [41]. This effect was weak (95% confidence interval around the odds ratio almost reached 1.0), limited to nulliparas, and has not been confirmed by other observational studies or by the three RCTs potentially able to verify such a benefit. On the contrary, observational studies of several different designs raise the strong likelihood that episiotomy actually increases the risk of anal sphincter damage. The use of midline episiotomy has consistently been found to be the strongest risk factor for a subsequent severe tear, even after controlling for confounding variables [17, 38-41, 61]. A causal relationship could be definitively established by a RCT. Unfortunately, the only RCT of midline episiotomy to date had limited power to confirm this causality in its "intention to treat" analysis because of the large number of incisions performed in its "restricted use" arm. Nevertheless, an analysis of the data by actual perineal management provides strong reinforcement of the conclusion of the observational studies [23].
The situation is less suspicious for mediolateral episiotomy: only two studies of reliable design [26, 39] reported an increased risk of deep laceration with mediolateral episiotomy, while most studies, including four RCTs, have uncovered no positive or negative effect.
Episiotomy versus spontaneous tear Having dealt with the question of third-degree tears, we turn to the issue of the relative perineal damage of episiotomies and spontaneous lacerations, absent consideration of anal sphincter damage. To judge the preferability of one over the other we must consider both the severity and the frequency of the injuries.
If an episiotomy were considered, contrary to intuition, equivalent in morbidity to an intact perineum, there could be little doubt that the procedure reduces the incidence of first- and second-degree injuries. This supposition is supported by both observational studies [9, 17, 21, 37, 39] and RCTs [47, 50]. However, as noted by Gass et al (among others), "To the patient they are not equivalent since she must undergo the incision, incision repair, and recovery. If we use a description of the tissue levels incised during an episiotomy, it is more appropriate to say that the episiotomy is the equivalent of a second degree laceration." [37]
Because "severity" of perineal damage is not intrinsically a quantifiable property, the most logical comparisons to make are patients' reports of symptoms (such as pain) and objective measures of specific features of the damage (such as infection). Many studies have addressed some aspect of the relative severity of episiotomy and spontaneous tears.
Pain during delivery. There appears to be only one study that includes relevant data on the pain felt by women during delivery. Röckner et al [64] reported a 15% incidence of pain during episiotomy (mostly mediolateral), versus none for a spontaneous tear, either second- or third-degree. Pain relief during repair was "satisfactory" for both groups. Postpartum pain. Thacker and Banta could find only one paper specifically addressing the comparative pain of episiotomy and spontaneous lacerations; it reported more pain one week after delivery for women with episiotomy [1]. Since then, five observational studies and all five RCTs have included information on the relative pain experiences in the immediate postpartum period. Authors of two consecutive letters in the British Medical Journal in 1982 presented their own data on postpartum perineal pain. Lee reported that ten percent of patients with episiotomies were still experiencing pain six weeks after delivery, but none of those with second-degree tears did [65]. Woinarski and Wright claimed that they could detect no difference in pain between women with episiotomy and those with second-degree lacerations [66]. Neither letter specified the type of episiotomy used. In the absence of fuller presentations of methods, these reports can be afforded little weight.
In the process of trying to develop an objective, standardized scale for reporting the healing of perineal trauma, Hill mentioned her findings of perineal pain in 94 patients less than 24 hours postpartum [67]. She reported only that "women who sustained an episiotomy with laceration experienced significantly more pain [on a zero to ten scale] than those with a laceration only." With no further information on parity, intrapartum procedures, type of episiotomy, or depth of laceration, this incidental statement by itself contributes nothing to the present question.
In Sweden, Larsson et al's patients, using a visual analog scale, reported significantly more pain with mediolateral episiotomy than after spontaneous laceration (apparently including only those requiring repair, though this is not made clear), on postpartum days one, three, and five [12]. This difference applied to both nulliparous and parous women, though statistical significance was lost by day five for the former.
Their compatriots, Röckner et al, discovered that Stockholm patients with episiotomy used more analgesics, reported more pain, and exercised less due to the pain than those with spontaneous second- or third-degree tears [64]. In Hørsholm, Denmark, Thranov et al found no difference in reported pain between patients with or without episiotomy, even though both research groups were studying nulliparous deliveries by nurse midwives in 1984, and only (or primarily) mediolateral episiotomies [20]. The discrepant results are even more puzzling since Thranov et al excluded operative deliveries, excluded patients with anal sphincter tears, and included lower degrees of perineal trauma in their non-episiotomy group, all of which should have the effect of increasing the relative pain in the episiotomy group.
On the second postpartum day, Dutch patients reported a 36% incidence of "frequent or continuous pain" after mediolateral episiotomy, 25% after a spontaneous tear (unfortunately including both first- and second-degree), and 7% with an intact perineum [68].
No observational study has compared the pain of midline episiotomy to spontaneous lacerations.
The three RCTs of mediolateral episiotomy followed the track of the observational studies in arriving at conflicting answers to this question. Harrison et al found no difference in pain on the first four postpartum days between patients with episiotomy, with second-degree spontaneous tears, or first-degree laceration, though all three groups had more pain than those with no perineal damage [43]. Sleep et al only surveyed their patients at ten days postpartum; no difference was seen between the liberal and restrictive episiotomy groups [47]. House et al saw no significant difference in perineal pain, but more tenderness in the liberal use group, at three days postpartum (though, as noted above, the patients with the most favorable outcomes were disproportionately excluded from analysis) [48]. The Argentine Episiotomy Trial Collaborative Group surveyed their patients at the time of hospital discharge [49]. Although they gave no information on how the pain was assessed, 38% more women reported residual perineal pain in the liberal episiotomy group than in the restrictive group.
The only RCT to use a previously standardized and validated pain scale is that of Klein et al [50]. They detected no overall difference between the two trial arms in perineal pain on days one, two, or ten, when analyzed by intention to treat. When re-analyzed by treatment actually received, parous patients with spontaneous tears had significantly less pain than those with episiotomies [23]. Nulliparous patients had an apparent difference, falling just short of statistical significance. Significance is retained when the parity groups are combined.
Long-term pain. Six studies have addressed the issue of long-term pain caused by perineal damage. At 8 to 12 weeks postpartum, no patient contacted by Larsson et al was experiencing any perineal pain, regardless of the type of birth injury [12]. Although Weijmar Schultz et al found that more average pain was reported at six weeks than at six months, there was no statistically significant difference between those with episiotomy, first- or second-degree tears, and intact perinea [68].
The RCT of House et al reported "no differences [in pain or tenderness] between the management groups at 6 weeks and 3 months. There were no patients with more than minimal perineal discomfort at 3 months" [48].
In their RCT, Sleep et al observed, at three months postpartum, comparable frequencies of "mild," "moderate," and "severe" pain between the liberal and restrictive use of episiotomy allocation groups [47].
Since the publication of Thacker and Banta's review [1], only two papers have found a difference in long-term perineal pain between episiotomies and spontaneous tears. At three weeks, Röckner et al's patients with mediolateral episiotomy had more pain during sitting, walking, defecation, and micturition than those with second-degree tears, though the difference was not statistically significant in the last two categories [64]. At three months, the groups differed in reported pain only while sitting, again in favor of those with spontaneous lacerations.
In their original paper, Klein et al did not report on long-term pain [50]. In the re-analysis, these data were presnted, although not by the original random allocation groups [23]. Similar percentages of women who experienced a spontaneous laceration and who had a non-extended midline episiotomy reported some degree of pain at three months. However, of those with any pain, the former group had less frequent and less severe pain.
Dyspareunia. Five observational studies and three of the RCTs collected data on postpartum dyspareunia, time to resumption of sexual intercourse, or both. In South Africa, Bex and Hofmeyr surveyed women who had delivered their first child at Johannesburg Hospital 12 to 24 months previously [69]. Current rates of dyspareunia were, counterintuitively, 38% after mediolateral episiotomy, 0% after second-degree tear, and 17% with an intact perineum. Current frequency of intercourse paralleled this distribution. At three months postpartum, the intact group had had less dyspareunia than the others, which were comparable. The very low rate of survey return (22%), the small numbers included (49 patients with vaginal deliveries), and the retrospective nature of some of the questions (asking women whether they had experienced dyspareunia on a specific date up to 21 months in the past, for example) render the data essentially useless.
Röckner et al reported no difference in time to resumption of intercourse or in dyspareunia at three months between women with mediolateral episiotomy and those with spontaneous second-degree or third-degree tears [64].
Conversely, a survey of London women five to seven weeks after delivery found that the presence or absence of episiotomy had no effect on the likelihood of a woman having resumed intercourse by the time of the interview, while a spontaneous laceration did delay such resumption, proportionate to its degree [70]. Neither outcome increased the frequency of dyspareunia at first postpartum coitus.
In still different findings, 16% of the patients queried by Larsson et al had dyspareunia 8 to 12 weeks after an episiotomy versus 11% after spontaneous laceration (all degrees combined), a significant difference [12].
When Weijmar Schultz et al [68] compared their patients with a first- or second-degree tear to those with a mediolateral episiotomy, they discovered that the former group resumed sexual activity sooner but, paradoxically, had more dyspareunia at six months. Their results are confounded by a difference between the groups, in favor of the episiotomy subjects, in suture technique known to affect the degree of postpartum pain [71-72].
In the RCTs, Sleep et al noted earlier return to intercourse among the patients with the lower episiotomy rate, but no difference in dyspareunia up to three months postpartum [47]. Further follow-up at three years still revealed no difference [73]. House et al noted a slightly longer time to resumption of intercourse in the liberal use group (6.5 weeks) than in the restrictive group (5.5 weeks) [48].
Klein et al initially found no difference between the allocation groups for either measurement [50]. However, when re-analyzed by actual perineal management, pain at first postpartum intercourse was less among those with spontaneous tears than among those with episiotomies, while fractions having resumed sexual relations at six weeks and level of sexual satisfaction were similar [23].
Healing problems. Three of five observational studies revealed more problems with early postpartum perineal healing after episiotomy than after spontaneous laceration [12, 64, 74]. It is difficult to know exactly what was being measured; these investigators used subjective evaluations and vague terms ("disturbed primary healing," [12] "restoration of the tissue's normal function," [74] and "wounds not healed" [64]). The fourth observational study used the more specific parameter "wound dehiscence," and found no difference between women with episiotomy and those with spontaneous laceration [68].
Lastly, Hill found no difference on a standardized rating scale between patients with episiotomy only, episiotomy with extension, and spontaneous laceration [67]. For reasons mentioned previously (section b., above), this incidental finding has little scientific value.
Three of the RCTs of mediolateral episiotomy included data on this topic. Harrison et al reported no cases of "wound breakdown or delayed healing" in either allocation group [43]. The Argentine Episiotomy Trial Collaborative Group detected "dehiscence" and "healing complications" (not specified) in 9.4% and 29.8%, respectively, of the patients allocated to liberal use of episiotomy, compared to 4.5% and 20.5% in the restrictive use group, both significant differences [49]. House et al examined patients for "significant granulation" in the perineum at three days postpartum, and found it in a similar percentage of women in the liberal (8%) and restrictive (12%) trial arms [48].
Larsson et al examined patients in later follow-up (8 to 12 weeks) for perineal healing problems, specifically scarring, asymmetry, and pain with palpation [12]. One or more of these was found in 11% of women having undergone mediolateral episiotomy, but only 4.8% of those with spontaneous lacerations. House et al also examined about one-half of their subjects at six weeks and three months postpartum; no differences between the two management groups were seen [48].
The Montreal trial of Klein et al included a survey of its subjects at three months postpartum [50]. No difference in a subjective sensation of "perineal bulging" was noted between women in the liberal and restrictive episiotomy use groups.
Incidentally, a recent case-control study has confirmed earlier speculation that human papillomavirus infection predisposes the patient to episiotomy dehiscence [75]. The frequency of this complication of episiotomy may therefore increase as our HPV epidemic widens.
Wound infection. Reynolds and Yudkin, in their four-year retrospective look at labor management in one English hospital noted no change in perineal infection rate as the use of mediolateral episiotomy dropped from 52.4% to 27.9% [9]. Two of three observational studies providing usable data on this question found much greater rates of wound infection after mediolateral episiotomy than after spontaneous laceration — five times higher (10% versus 2%) in one [12] and eleven times higher (22% versus 2%) in the other [64]. In contrast, Weijmar Schultz et al found no difference [68].
Saunders et al performed a retrospective study of the influence of the length of the second stage of labor on neonatal and maternal morbidity [76]. An incidental finding in their logistic regression analysis was that episiotomy (presumably mediolateral, given the London setting) had no effect on the risk of infection.
In the first episiotomy RCT, Harrison et al had no cases of infection. That of House et al recorded no difference in infection risk between allocation groups (4% and 5%) [48]. The most unbiased and reliable information comes from the Argentine trial [49]; low and essentially identical infection rates (1.6% and 1.8%) were seen in the two trial arms.
Only one paper provides data on infection following midline episiotomy [77]. Owen and Hauth retrospectively reviewed records of five years of births at the University of Alabama Hospitals. Postpartum perineal infections were rare, with only ten cases in 20,713 deliveries. Although episiotomies were performed in 55% of vaginal births overall, 100% of the infectious complications were preceded by a midline episiotomy.
Edema and hematoma. As with infection, the incidence of postpartum hematoma did not change with the dropping episiotomy rate in Reynolds and Yudkin's hospital [9]. Röckner et al reported significantly higher rates of both edema and hematoma (25% and 38%, respectively) after episiotomy than after second- and/or third-degree lacerations (8% and 13%) [64]. Weijmar Schultz et al [68] concurred with the increase in hematoma after episiotomy (rates not reported), but saw no difference in edema. Harrison et al [43] found that the severity of both of these conditions was similar between women with episiotomy and spontaneous second-degree tear. The Argentine Episiotomy Trial Collaborative Group measured only hematoma; rates were about 4% in both trial arms [49].
Ease of repair. It is frequently asserted that an episiotomy is easier to repair than a spontaneous laceration. There is still no objective confirmation of this claim. Even if it is true, the ease of repair for the accoucheur could be entertained as a reason to perform an episiotomy only if it were definitively shown not to harm the patient in the process. Almost none of the trials discussed in this review include any information on this point. Those that do mention it only in passing as, for example, Thorp et al: "All of the lacerations that occurred in the absence of episiotomy were easy to repair" [21].
The best evidence on this matter is provided by Sleep et al [47]. Their RCT found more suture material used in the liberal episiotomy group than in the restrictive group. The former also required more suturing time, which eliminated the overall time advantage that it otherwise would have enjoyed due to somewhat shorter second stage.
Long-term morbidity. Finally, I take note of two publications that may indicate the presence of more long-term morbidity from episiotomy than from spontaneous tears. Perry et al devised a summary measurement of the magnitude of anal sphincter tone in eight radially arranged sectors [78]. This "vector symmetry index" (VSI) is lower in patients with focal sphincter muscle defects. From a group of 40 Nebraska women with fecal incontinence but no history of sphincter injury, the 28 with a history of episiotomy (presumably midline) had a significantly lower mean VSI that the 12 with no history of episiotomy (of whom 8 were parous). This implies that at least some women with symptoms of fecal incontinence have had unrecognized anal sphincter damage from episiotomy.
In Santa Barbara, California, Corman noted that of 28 consecutive patients referred to him for surgical treatment of intractable fecal incontinence, all attributed the symptoms to obstetrical injuries [79]. Of these, 27 had had an episiotomy; records established that 20 were midline, and in seven cases the incision type could not be ascertained. Although interpreting numerators without denominators is hazardous [80], it is unlikely that such a high episiotomy rate would be found among matched controls.
Frequency of perineal damage. If a practitioner were able to anticipate with perfect specificity which women would experience a second-degree or greater tear, use of episiotomy in only those patients would obviously result in no increase in the number of women experiencing perineal damage at that depth. However, as mentioned previously, no one has yet demonstrated such prognostic ability. Lacking it, most accoucheurs perform episiotomies in many cases that would otherwise have ended with less trauma. Every observational study that supplies data on this subject has concluded that an increased use of episiotomy is inversely associated with the likelihood of an intact perineum (or at least no need of repair) [9, 11, 17-19, 37, 39]. All three RCTs with a design capable of producing such data also found that lower rates of episiotomy — midline or mediolateral — resulted in a less frequent need for perineal suturing [47, 49-50]. No study of any design has contradicted this conclusion. It can be stated definitively that in current obstetrical practice, "the most common cause of perineal damage is episiotomy." [81]
Summary. The best recent evidence comparing the injury of episiotomy and spontaneous laceration can be summarized as follows: At the time of delivery, episiotomies cause more pain than spontaneous tears. In the first several postpartum days, both midline and mediolateral episiotomy probably cause more pain than spontaneous lacerations, though the evidence is mixed. There is no evidence that any episiotomy causes less long-term (three weeks or more) pain than a spontaneous laceration. There is fairly evenly divided evidence as to the existence of an advantage in the long-term pain of a spontaneous laceration over an episiotomy; a definitive conclusion on this point will require further research. A spontaneous tear results in earlier return to sexual intercourse than a mediolateral episiotomy, but no major difference in long-term dyspareunia. Liberal versus restrictive use of midline episiotomy causes no difference in either of these outcomes. Mediolateral episiotomy is associated with more short-term and long-term improper healing than spontaneous tears; no comparable data are available for midline episiotomy. Neither liberal nor restrictive use of mediolateral episiotomy has convincingly been shown to increase rates of postpartum perineal infection, edema, or hematoma. There is no evidence that episiotomies are easier to repair than spontaneous lacerations. Liberal use of mediolateral episiotomy results in the overall use of more suturing time and material. The overall frequency and severity of perineal damage is increased by liberal use of episiotomy. In short, episiotomy cannot be said to have demonstrable advantage over a spontaneous laceration in the frequency or in any measure of the severity of perineal damage yet studied, and its liberal use clearly increases the overall amount of perineal trauma and consequent morbidity.
Prevention of anterior lacerations The last of the three purported benefits of prophylactic episiotomy on obstetric lacerations is that its use reduces the incidence of anterior perineal lacerations. This is actually the easiest claim to discuss, since the conclusion has been nearly unanimous across all study designs addressing it.
Comparing women with episiotomy to those with second- and third-degree lacerations, Röckner et al observed a greater number of "tears of labia/clitoris" in those with spontaneous injury (33% versus 18%) [64]. A year later the same group, using a more inclusive review of hospital records to compare all nulliparous women with or without episiotomy (rather than just those experiencing significant perineal damage), reached a very similar conclusion: 22% rate with an episiotomy, 36% without [10].
When Thranov et al retrospectively divided their patients according to the episiotomy habits of the attending midwives, the group with the lowest episiotomy rate had the highest (34%) frequency of anterior mucosal tears [20]. The groups with medium and high use of episiotomy had little difference in the amount of such damage (21% and 25% respectively). Analysis by the presence or absence of episiotomy showed that "significantly more women who did not undergo an episiotomy had tears in the labia minor and clitoris area, but these women did not have a significantly increased frequency of postpartum pain when compared with all [nulliparas] without an anterior tear ... and the postpartum pain did not persist any longer."
In Rooks et al's multicenter study of U.S. birth centers, 15.2% of patients had periurethral tears without episiotomy, compared with 5.4% after episiotomy [34].
Two of the RCTs have collected data confirming these findings. The Argentine investigators documented an incidence of "anterior perineal trauma" of 19.2% in the restrictive use group and 8.1% in the liberal use group (relative risk 2.36) [49]. Klein et al noted a trend towards more "periurethral/labial tears" in the restrictive use group, especially for parous women, though it did not reach statistical significance [50]. (This may be due to the relatively small difference in the actual episiotomy rate between the trial arms, as discussed above.) These authors noted that "most women did not complain about anterior trauma. Their pain related principally to symptoms of posterior trauma. Thus, in both trial arms, women of both parity groups who retained an intact perineum, had less perineal pain, with or without anterior trauma, than women with any other perineal outcome."
In North Carolina, Thorp et al, comparing one resident using a restrictive policy of midline episiotomy to liberal use by others, found "no differences in the rate of periclitoral and periurethral lacerations" and "no cases of injury to the urethra or the bladder" [21]. This appears to be the only study reporting no protective effect of episiotomy.
It seems clear that episiotomy does prevent anterior perineal injury, though such injury carries a very low incidence of pain or other morbidity.
It has been postulated that an increased incidence of periurethral trauma could lead to more urinary incontinence by damage to the urinary sphincter [81-82]. The association between episiotomy and urinary incontinence will be explored in the next section.
Summary The use of mediolateral or midline episiotomy does not decrease the risk of anal sphincter damage, and a midline episiotomy almost surely increases this risk. Episiotomies increase the frequency and severity of perineal damage compared to what would occur spontaneously. An episiotomy will reduce the risk of anterior tears, but it does so at the expense of the much greater morbidity of posterior perineal injury.
Prevention of pelvic relaxation The second major advantage claimed for episiotomy is that it prevents relaxation and its sequelae, such as urinary incontinence, cystoceles, and rectoceles. Research on this question has used two main outcome variables: subjective reports of urinary incontinence and objective measures of pelvic floor muscle strength.
Symptomatic urinary incontinence At the time of Thacker and Banta's review [1] no published research existed specifically addressing whether episiotomy can reduce the later development of urinary incontinence. Since then, three retrospective patient surveys and one prospective cohort study have been presented. Most important, two RCTs of episiotomy have included urinary incontinence as outcome variables, one with long-term follow-up.
Two of the three patient surveys were Scandinavian (as is a disproportionate share of all research on episiotomies). I have previously discussed the one by Thranov et al [20]. In their nulliparous patients (parous at the time of the follow-up survey, obviously), 61% had experienced urinary incontinence at some time postpartum, 30% for at least three months, and 18% for six months or longer. No difference was seen in these percentages when grouping the patients by low, medium, and high use of episiotomy by their midwives.
Röckner, first author of one of the principal studies examined in the last section (comparing postpartum symptoms after episiotomy and spontaneous tears) [64] surveyed the same patients again four years later to inquire about the later development of incontinence [83]. The two groups had similar subsequent obstetric histories and equally high (90%) survey response rates. They were very similar in percentages reporting development of urinary incontinence after first and second deliveries, and in the prevalence and severity of current stress incontinence.
Of 290 German women delivering vaginally, 5.6% experienced stress urinary incontinence twelve weeks postpartum with episiotomy, compared to 9.4% without [84]. This difference was not statistically significant, and no adjustment was made for such potential confounding factors as parity, anesthesia type, fetal weight, and length of labor.
In Copenhagen, Viktrup et al attempted to construct a natural history of pregnancy-related stress incontinence by surveying 305 nulliparous women during pregnancy, a few days postpartum, three months later, and at one year after delivery if symptoms had been present at three months [85]. Among women who experienced stress incontinence de novo after delivery, average second stage duration, fetal head circumference, and birth weight were all greater than in the patients not developing incontinence. Patients with mediolateral episiotomy were more likely to develop subsequent incontinence than those who had none. The magnitude of this difference was not reported, though the investigators asserted statistical significance. However, this relationship was confounded by the more frequent use of episiotomy in women with longer second stage, and no statistical adjustment was made for this. At three months postpartum, none of the intrapartum factors continued to exert an influence on the prevalence of symptoms. The authors therefore concluded that if episiotomy increases the risk of developing symptomatic stress incontinence, it is a transient effect.
Klein et al's RCT of midline episiotomy found a nonsignificant trend toward increased urinary incontinence at three months postpartum among their (formerly) nulliparous patients with restrictive use of episiotomy, but a significant opposite relationship among parous women [50]. Correction for preexistent symptoms reduced this latter difference out of the range of statistical significance as well, though the direction of the effect of episiotomy remained contrary in nulliparous and parous women. No explanation for this phenomenon readily presents itself, other than random sampling differences.
The most useful information on the effect of mediolateral episiotomy on stress incontinence comes from the RCT of Sleep et al [47] and its later follow-up [73]. At three months postpartum, about 19% of women in both allocation groups were experiencing some degree of urinary incontinence, and 6% sometimes wore a protective pad. A detailed set of questions distributed three years later discovered there still to be no difference between the groups in any measure of urinary incontinence, whether or not a subsequent delivery had occurred [73].
Pelvic floor muscle strength Eleven groups of investigators have, in the last 13 years, used objective, instrumented measurements of pelvic floor musculature or urinary sphincter strength to assess the changes caused by childbirth and episiotomy.
Using a modification of the perineometer (a fluid-filled condom connected to a manometer) used by Kegel in his pioneering work [86], Gordon and Logue measured the magnitude and duration of a levator muscle contraction in 84 suburban Londoners [87]. Four distinct groups, all one year postpartum, were compared: women who had delivered with no perineal trauma, second-degree spontaneous tear, episiotomy (type not specified; presumably mediolateral), and forceps plus episiotomy. Two control groups were also studied: nulliparous women and women who delivered abdominally. Quite surprisingly, the means and distributions of the maximum intravaginal pressures generated were very alike between all the groups.
Samples et al of the University of Florida used a similar water-filled intravaginal balloon to assess circumvaginal muscle strength in parous and and nulliparous women not postpartum, and postpartum (less than 16 weeks) patients [88]. Those who had recently experienced vaginal delivery showed lower mean pressure generation than either post-cesarean section patients or nulliparas; no difference was seen between those with and without episiotomy. The value of this study is limited by small numbers and by poor accounting for many patients with incomplete data collection.
The other nine studies applied their various measurements to women both before and after delivery to document changes induced by the birth. Data on additional differences due to presence or absence of episiotomy are usually a small part of the research.
In Manchester, England, Allen et al mapped the natural changes in perineal muscle function in late pregnancy and up to two months postpartum in 96 normal nulliparous women using, among other techniques, pelvic floor electromyography (EMG) [89]. They documented a decline in the maximum pelvic floor contraction strength after delivery that had not fully recovered at two months postpartum. This change was attributed to partial denervation of the pelvic floor at the time of delivery in about 80 percent of nulliparous women. The presence of episiotomy and/or spontaneous perineal tears had no significant effect on the nature of these changes.
Another British group measured the pudendal nerve terminal motor latency (PNTML), an increase in which is thought to be associated with eventual development of anal incontinence [90]. Sultan et al observed a significantly prolonged PNTML at seven weeks postpartum compared to during pregnancy, especially after a woman's first delivery. Neither the use of episiotomy nor the presence of perineal tears modified this degeneration.
Smith et al performed EMG of the pubococcygeus muscle in women symptomatic for stress incontinence and/or genitourinary prolapse and in asymptomatic controls [91-92]. They demonstrated that stress incontinence was associated with a higher pelvic floor muscle motor unit fiber density. The background information on the patients revealed that more asymptomatic than symptomatic women had had an episiotomy during childbirth; this difference was not similarly present for spontaneous lacerations or intact perinea. The authors commented, "The reduced occurrence of stress incontinence or prolapse in women who had an episiotomy and no perineal tear supports the claim of reduced pelvic floor injury when episiotomy is performed" [91]. Several caveats are in order: (1) The authors acknowledged that their patients' "clarity of recall was variable," and they made no attempt to verify the nature of the original perineal injury with hospital records. (2) This data was not a primary focus of the research, but an incidental discovery; EMG results were not even tabulated according to the type of perineal damage. (3) The determination of prolapse (and, hence, assignment to the symptomatic or asymptomatic group) was made subjectively by an investigator not blinded to the obstetric history. (4) No inquiry was made about possible confounding variables except birth weight. As presented, then, the data are not strong enough to support the authors' assertion.
In a series of articles, Snooks et al demonstrated damage to the innervation of the pelvic floor muscles occurring routinely after vaginal delivery, but not after cesarean section [93-98]. This was measured by EMG determination of motor unit fiber density; this density increases with denervation-reinnervation injury. They found no difference between episiotomy and spontaneous first- or second-degree tears in terms of immediate postpartum pudendal nerve damage, or in anal sphincter motor unit fiber density at two months postpartum.
Röckner et al used an appealingly simple means to assess pelvic floor strength — a series of small weighted cones [99]. They recorded the mass of the heaviest cone that could be retained intravaginally for one minute while standing. Eighty-seven Swedish nulliparas were studied. Those undergoing cesarean section had no change in the mean pelvic floor muscle strength at eight weeks postpartum compared to 36 weeks' gestation. However, women delivering vaginally saw a 20% decline with an intact perineum or a spontaneous laceration, and a 33% percent decrease after mediolateral episiotomy. This difference was significant and did not appear to be confounded by length of second stage, use of operative delivery, or the infant's weight or head circumference.
Of the five RCTs on episiotomy described earlier in this review, only the Canadian study included measures of pelvic floor function [50]. Klein et al, using an intravaginal transducer, recorded the mean EMG voltage change generated during six consecutive voluntary pelvic floor muscle contractions. Contrary to all other studies, they documented an increase in contraction strength at three months postpartum compared to trial entry (mid-third trimester); this held for all four combinations of parity and allocation group. Liberal or restrictive use of episiotomy had no effect on pelvic floor functioning at three months postpartum.
The only one of these studies to focus specifically on the urinary sphincter mechanism was that of van Geelen et al [100]. They followed 43 nulliparous Dutch women through pregnancy and the puerperium to observe changes in the urethral pressure profile as assessed by a transducer catheter. Although multiple measured variables changed between late pregnancy and eight weeks postpartum, the direction and magnitude of the changes were unaffected by the use or non-use of mediolateral episiotomy.
Moving away from instrumented assessments of pelvic floor strength, Sampselle et al devised a numerical scale based on several characteristics of a woman's contraction of the circumvaginal muscles around an examiner's fingers [101]. Their patients showed a decrease from mid-third trimester to six weeks postpartum after vaginal delivery, but not after abdominal delivery. The authors claimed to be able to distinguish between patients who delivered with intact perinea (mean score 8), with episiotomy (score 7.25), or with spontaneous laceration (depth not specified; score 6). This claim is not credible, since they had four or fewer patients in each of these groups, and since the examiners assigning these inherently subjective scores were not blinded to the perineal status.
A very similar scale was developed by Worth et al [102]. They claimed that no differences were seen between women based on age, parity, or history of episiotomy. However, no data were presented to support this conclusion.
Summary There is no evidence that episiotomy reduces the incidence of early or late postpartum urinary incontinence, or that it moderates the normal loss of pelvic floor muscle strength usually experienced after vaginal delivery. One well-designed study found a marked impairment in pelvic floor muscle strength at eight weeks postpartum in patients with mediolateral episiotomy when compared to those with spontaneous or no laceration [99]. This conclusion has not been corroborated by other investigative methods. No research has found a persistent difference in objective pelvic floor strength between episiotomy and non-episiotomy patients.
Some have argued that the postulated benefit of episiotomy to pelvic floor integrity cannot be achieved by modern obstetric practice. They point out that episiotomy performed by current norms (when a few centimeters of fetal scalp are exposed) is too late to prevent the damage caused by passage of the head through the pelvic sling [81, 103-109]. Advocates of this opinion might assert that a protective effect would have been present in these studies had the episiotomies been performed before the presenting part reaches zero station, as they prescribe. It is certainly true that none of the research reviewed herein disproves long-term benefits of an episiotomy so timed. It is equally true that proponents of this technique have produced no research of their own to substantiate their views.
It should be noted, for clarity, that most of the authors cited in the preceding paragraph are not themselves proponents of early episiotomy, but are quoting the arguments of earlier publications. In fact, I have been able to identify only two papers published since 1980 actually favoring episiotomy before the presenting part reaches the pelvic floor [103, 109]. Perhaps this position has finally lost sway.
Prevention of fetal injury The last main category of claimed benefit for episiotomy is prevention of fetal injury, specifically intracranial hemorrhage and intrapartum asphyxia. I will also discuss the commonly accepted precept that an episiotomy should be performed in cases of second-stage fetal distress or shoulder dystocia.
Intracranial hemorrhage The two rarer types of neonatal intracranial hemorrhage, subdural and subarachnoid, are both directly related to birth trauma [110]. I am unaware of any research on the relationship between episiotomy and these birth injuries. Probably the closest relevant work is that of O'Driscoll et al, who found that forceps had been used in all 27 of their cases of traumatic intracranial hemorrhage [111]. Because the infants involved were all firstborns with instrumented deliveries between 1963 and 1979, it is likely that all or nearly all of these births also involved episiotomy. It would not be possible to separate the effects of these two interventions in this study.
Intraventricular hemorrhages (IVH) are multifactorial in origin. Labor and its management may contribute to IVH by causing "elevations of cerebral venous pressure as well as intermittent fetal hypoxia and acidosis." [112] However, a causal relationship has been difficult to establish. Studies are conflicting as to whether cesarean section reduces the incidence of IVH in premature infants [112-113]. It is not surprising, then, that the presumably more subtle difference of use or non-use of episiotomy in vaginal delivery has not been demonstrated to influence the risk of IVH [113].
Four retrospective uncontrolled studies pertinent to this question have been published since 1980. The weakest of these is the work of Barrett et al [114], conducted at Vanderbilt University. Its principal deficiency is the absence of imaging studies to detect IVH; only clinical criteria and autopsy findings were used to establish this diagnosis, meaning that lower grades of IVH could easily have been missed. Among 46 vaginal deliveries of infants weighing 751-1000g, neither the neonatal mortality nor incidence of IVH distinguished those managed with episiotomy from those without.
de Crespigny and Robinson performed ultrasound examinations of 118 low birth weight (LBW; defined as less than 1500g in this study) neonates in Melbourne, Australia [115]. Birth records were then reviewed. Among 69 vaginal births, presence or absence of episiotomy did not change the incidence of IVH in breech, forceps, or spontaneous vertex deliveries.
Similarly, researchers in Liverpool reviewed records of 97 consecutive LBW babies, all of whom received serial ultrasound scans [116]. Lobb et al were the only group to stratify their patients by birth weight and gestational age, since these factors can have an impact on both IVH and on the use of episiotomy. In the only strata with enough infants for meaningful comparisons to be made, use of episiotomy did not appear to influence the risk of mortality or IVH among infants of 25 to 28 weeks' gestation or of 751 to 1250g birth weight. They conclude that "When [LBW] babies of similar weight and age are considered, the use of episiotomy appears to hold no advantages. ... In the absence of data to support the routine use of episiotomy in pre-term delivery this potentially harmful procedure should be avoided." [116]
Finally, two Detroit researchers challenged the premise underlying the argument for use of episiotomy in LBW infants [117]. Welch and Bottoms retrospectively studied 101 infants with birth weight of 500 to 1500g. No factor related to increased intracranial pressure (presence or absence of labor, duration of rupture of membranes), including use of episiotomy, was associated with greater risk of IVH. The authors conclude that "fetal head compression is not a major determinant" of IVH.
Intrapartum asphyxia Given the rarity of true perinatal asphyxia [118], it is unlikely that any study will have sufficient power to measure an independent effect of episiotomy on its occurrence. Other outcome variables have been studied as surrogate or intermediate markers. Most common among these has been the Apgar score.
At a university hospital in Jamaica, The [119] focused his retrospective investigation on LBW (less than 2500g) infants without known prenatal complications (e.g., preeclampsia, gestational diabetes, growth retardation). Neonatal mortality was equal with or without episiotomy. Among live births, use of episiotomy had no clinically significant influence on one- and five-minute Apgar scores for either nulliparous or parous women.
Most other studies on episiotomy specifically exclude pre-term and/or LBW babies to avoid confounding effects; consequently, neonatal mortality becomes so rare as to be unusable as an outcome variable. Nearly always, Apgar scores are the only measurement of fetal condition reported. In every observational study which includes such data, Apgar scores were not affected by the use (or frequency of use) of episiotomy [9-10, 12, 20-22, 30, 76]. The RCTs weigh in with similar unanimity; restrictive use of episiotomy does not result in a different distribution of Apgar scores than liberal use [43, 47-50].
Several other fetal outcome variables have been included in one or more studies. No effect of episiotomy was seen for rates of infant resuscitation [9], NICU admission [9, 47, 50, 76], meconium [18], unspecified "birth injuries" [17], or unspecified "baby complications" [18].
The only exception to this uniformity is the report of Friese et al [120]. They report that among the 1458 term vaginal births at a Mannheim (Germany) hospital in 1993, those delivered with episiotomy had a significantly lower umbilical artery pH (7.25) than those without (7.33). They argued that in the 49% of deliveries in which it was used, episiotomy was necessary "to prevent further fetal hypoxia by shortening the second stage of labor." Unfortunately, these data are presented only in highly abbreviated form in a letter to the editor (challenging the conclusions of the Argentine RCT). Until further details are released, the inferential value of these results is minimal. In isolation, one could as easily interpret them as demonstrating an adverse effect of the episiotomy on the cord pH.
This leads to consideration of an indirect line of evidence of potential benefit of routine episiotomy on early neonatal outcome. If (1) the length of the second stage of labor is proportionate to the deterioration of fetal acid-base status, and if (2) episiotomy shortens the second stage, then one might expect to see results such as those of Friese et al [120]. Because the first component of this syllogism is independent of the use of episiotomy, it is outside the scope of this paper. Suffice it to say that the preponderance of published reviews appears to disclaim any arbitrary upper limit on the safe duration of second stage in a non-distressed fetus [ 1, 81, 121-125].
The second part of this syllogism — that episiotomy abbreviates the second stage — seems obvious, but actually has surprisingly little evidentiary support. Because it is a point of lesser importance, I will merely list the recent observational studies by their conclusions without consideration of their relative strengths.
The expected direction of effect is reported only by Reynolds and Yudkin [8]. No difference in length of second stage with or without episiotomy has been reported by five papers [10, 18-20, 64]. Four studies demonstrated a longer second stage with use of episiotomy [22, 30, 38, 126]. Three of these [30, 38, 126] can reasonably be understood as employing episiotomy to terminate the longest labors, but one is not so easily dismissed. In it, as discussed previously, Chambliss et al randomized patients to management by obstetric residents or midwives within the same hospital [22]. The midwives managed a shorter mean second stage (33 versus 45 minutes) despite less frequent use of episiotomy, oxytocin, and operative deliveries.
The RCTs add little support to this presumed benefit of episiotomy. Harrison et al compared those randomized to receive episiotomy and those who sustained a spontaneous second-degree tear; length of second stages were similar (35 and 32.5 minutes, respectively) [43]. Sleep et al mention in passing that the liberal use group had a longer average labor, but provided no data on this point [47]. House et al found no significant difference in the length of first or second stages [48]. Such information was not collected in the Argentine trial [49]. Klein et al saw a non-significant trend toward shorter second stage with liberal use of episiotomy in nulliparous women (84 versus 75 minutes), but no difference in their parous patients [50].
Fetal distress There remains the question of whether fetal distress is an appropriate indication for episiotomy. Such use is conceded even by many authors who take an otherwise dim view of the procedure [21, 50, 81, 121, 127]. This defense obviously depends on the assumption that episiotomy will abbreviate the delivery. As discussed in the previous section, there is little scientific rationale for this assertion.
That said, it must quickly be granted that the question "Does episiotomy shorten the second stage of labor?" is not equivalent to asking "Does episiotomy shorten the interval from its performance to delivery when late second stage fetal distress is diagnosed?" There is simply no published research on the latter query. Nor is there likely to be. Such a study would have to deal with the high incidence and low specificity of fetal heart rate "abnormalities" in the second stage [52-57] and the wide range of opinion as to which cardiotocogram features indicate distress needing intervention [128-129]. It is also unlikely that institutional review committees would allow or many clinicians participate in a randomized trial of episiotomy in the face of diagnosed fetal distress, given the prevalence of the assumption of its benefit.
Nevertheless, we need not simply abandon the issue. An RCT could be designed so that distressed fetuses are excluded and the accoucheur learns the patient's allocation (episiotomy or none) only after deciding that it was time to perform one. If episiotomy truly hastens delivery by a clinically significant amount, a fairly small trial of this design should have power to demonstrate it, since, say, a two-minute decrease in the crowning-to-delivery time will be more readily apparent than a two-minute decrease in the overall second stage duration. The results in healthy fetuses should be generalizable to those in distress.
Shoulder dystocia Episiotomies, sometimes including intentional proctoepisiotomy or bilateral mediolateral episiotomies, are commonly described as one of the first steps that should be taken to relieve shoulder dystocia. In a recent review, Piper and McDonald were able to identify only four published commentaries that questioned this assumption, despite the lack of published research to demonstrate its benefit [130]. Without doubt, the performance of a methodologically rigorous trial of any maneuver to relieve shoulder dystocia would present formidable technical and ethical obstacles.
In the absence of reliable data, the clinician must make a reasonable decision of the performance of an episiotomy in this critical moment. Considerations arguing against its use are (1) the concept of shoulder dystocia as a problem of bony disproportion, rather than a soft-tissue obstruction, and (2) the availability of apparently effective non-surgical techniques (e.g., McRoberts maneuver, maternal hands and knees position). In favor of its use are (1) wide anecdotal acceptance of its efficacy, (2) the need for expanded room in the outlet for intravaginal interventions (such as the Woods maneuver), and (3) the need to apply all available methods for a birth complication with such high fetal morbidity and mortality.
I have been able to locate only one published analysis of the use of episiotomy as a prophylactic measure against shoulder dystocia; this retrospective study found that its use did not appear to reduce the risk of this emergency [131].
Summary There is no substantial evidence that episiotomy reduces the risk of IVH in LBW infants, or that it improves any measure of neonatal outcome in term deliveries. Only one reliable study suggests a reduction in the length of second stage [8], while others find a contrary or null effect. No research has addressed the utility of episiotomy in fetal distress or shoulder dystocia, though the appropriateness of these indications is widely conceded.
Risks Nothing is so firmly believed as that which we least know.
- Michel de Montaigne
Most of the risks of episiotomy (anal sphincter damage, poor wound healing, infection, pain, and dyspareunia) have been addressed earlier in this review. In this section I will review reports of maternal blood loss, long-term morbidity of anal sphincter damage, psychosocial consequences, and miscellaneous other risks.
Blood loss Thacker and Banta summarized the literature to 1980 as showing "an increase of 300 cc or more for about 10 per cent" of women undergoing episiotomy [1]. Since then, three papers assessing risk factors for postpartum hemorrhage have been published, and five others have relevant incidental information. Regrettably, the only one of the five RCTs to collect data on blood loss was that of House et al [48]. Its finding of an increased loss in the liberal use of episiotomy group (272 vs. 214 mL) is seriously weakened by the study's previously-mentioned design and reporting flaws.
In Hong Kong, Duthie et al provided further confirmation of the long-recognized tendency of birth attendants to underestimate intrapartum blood loss [132]. Their only observation relevant to episiotomy research was that the time interval from the performance of a mediolateral episiotomy to its repair correlated with the measured blood loss. Because they studied no patients without episiotomy, comparative inferences cannot be drawn.
In the process of reporting a new method for measuring obstetric blood loss, Hill et al almost incidentally present the values obtained in 84 "randomly selected" patients from their Georgia hospital [133]. Episiotomy could not be analyzed as a modifier of blood loss in primiparous women, since all 29 received one. Comparative tests are of very low power even among multiparas, since 46 out of 55 received episiotomies. Nevertheless, patients with either a non-extended episiotomy or a spontaneous laceration had significantly more blood loss than those with intact perinea. The value of this data is minimal, since the number of patients was small in some groups, little other clinical information is given, no confounding factors (except operative delivery) are considered, and the blood measurement technique was not tested against established methods.
The work of Röckner et al has previously been discussed in detail [10, 64]. The additional observations relevant to this discussion are that patients with mediolateral episiotomy were more likely to have a visually estimated blood loss of over 600 mL than matched controls with spontaneous second-degree tears (29% and 17%, respectively) [64], or than the entire population managed without episiotomy (same percentages) [10]. No attempt was made to adjust for confounding variables.
Speculating that use of beta agonists shortly before delivery in failed tocolysis might inhibit third-stage uterine contractility, Essed et al measured blood loss after cord clamping in 129 Dutch women so treated and in 176 controls, all delivering preterm [134]. The primary effect was not seen. Use of mediolateral episiotomy was noted to increase the average postpartum blood loss by by 109 mL in treated patients and 125 mL in untreated controls. Some confounding is likely to have been present from duration of the second stage, and other confounding factors cannot be excluded, since statistical adjustment was not performed to isolate the effect of episiotomy.
Saunders et al investigated the effect of the duration of the second stage on neonatal and maternal morbidity [76]. In a logistic regression, use of an episiotomy (presumably mediolateral, given the British setting) was not a significant risk factor for estimated postpartum blood loss over 500 mL, contrary to the other reports discussed here.
Of the three major papers addressing risk factors for postpartum hemorrhage, only two are pertinent here, since one of them inexplicably failed even to mention episiotomy as a risk factor [135].
Stones et al derived data from a maternity database encompassing the entire North West Thames health region [136]. Quantitation of blood loss was by visual estimate only, but these researchers studied only those patients with a recorded value of 1000 mL or more, making it unlikely that cases of minor blood loss were included. Of those factors under the control of the accoucheur in a vaginal delivery, use of episiotomy (mostly mediolateral, presumably) was second in importance (relative risk 2.06) only to operative delivery (relative risk 2.39). Perineal tears did not significantly increase the risk over that seen with an intact perineum. No adjustment was made for confounding factors.
The most important study to date is that of Combs et al in San Francisco [137]. It is superior to other research in its use of objective criteria for the definition of a case of postpartum hemorrhage ("hematocrit decrease of 10 points or more between admission and the postpartum period" or receipt of a transfusion) and its use of a case-control design and multivariate analysis to control for confounding variables. Again considering only those factors under the control of the accoucheur, univariate analysis found association between hemorrhage and use of oxytocin, operative delivery, episiotomy, and epidural anesthesia. In the final "best fit" model, use of mediolateral episiotomy stood out as the most important of these factors (odds ratio 4.67); midline episiotomy also retained significance (OR 1.58), slightly below use of labor augmentation and operative delivery (each with an OR of 1.66). In this model, all spontaneous lacerations combined (cervical, perineal, and vaginal) displayed an OR of 2.05, compared to no laceration.
Morbidity of anal sphincter damage It used to be common belief that proper care of third-degree extensions of midline episiotomies would prevent long-term morbidity. Pratt, for example, wrote in 1942, "a third-degree laceration of the perineum, when properly repaired, heals as readily as if the muscle were not torn" [138]. Twenty years later, papers in the two leading American obstetrics journals concluded "In 1960 it would seem that the fear of a perineal laceration as the result of an extension of a midline episiotomy is unrealistic" [139] and "When necessary, complete perineotomy may be done with relative impunity. ... Extension of an episiotomy into the rectum is never to be regarded lightly, but in modern obstetrical practice this complication is not as portentous as formerly thought" [140]. After the passage of another fourteen years, Beynon tried to persuade her British colleagues that "a fear of rectal involvement is no longer a justifiable reason for opposing the widespread use of median episiotomy" [141]. Unfortunately, a cavalier attitude toward this complication remains apparent in some publications within the last decade [142-143]. Such a position is difficult to maintain in the light of more recent findings [144].
In this section I shall briefly survey the results of the last ten years of investigation into the morbidity of anal sphincter injury. In most cases, subjects include both those with spontaneous third-degree tears as well as episiotomy extensions; this assumes that, in terms of morbidity, the two are equivalent, though this surmise lacks scientific confirmation. These results are only relevant to a discussion of the risks of episiotomy if, as contended in section II.A.1. of this review, episiotomy does actually increase the chance of a patient's suffering sphincter damage.
Mellerup Sørensen et al identified 25 Danish women who had experienced perineal rupture during delivery, and compared them with controls matched for age, parity, and use of mediolateral episiotomy [145]. At 52 to 123 (mean 78) months after delivery, 42% of the cases described some degree of anal incontinence (25% for flatus, 13% for loose stools, 4% for normal stools), compared to none of the controls. When a sample of each group was tested with anal manometry, the cases demonstrated shorter anal sphincter length and weaker squeeze pressure than the controls.
In London, Sultan et al found that 47% of women with third-degree tears remained symptomatic 6 to 21 months after delivery, with anal incontinence (mostly to flatus, a few to liquid stool) and/or fecal urgency, compared with only 13% of controls [146]. Ultrasonography revealed internal and/or external anal sphincter defects in 85% of women with third-degree lacerations, in all of the symptomatic ones, and in 33% of controls. In those with third-degree tears, the injury tended to occur along the entire length of the sphincter and to both internal and external muscles; in controls the defects were shorter and usually involved only one of the sphincter muscles. Anal manometry recorded lower maximal resting pressure, lower maximal squeeze pressure, and shorter canal length in patients with third-degree lacerations than in controls. The authors believe that these defects are likely to predispose even the currently asymptomatic patients to later fecal incontinence. However, in a separate paper, the same team found an association between performance of a mediolateral episiotomy and the development of occult sphincter defects only in univariate analysis; it disappeared as a significant factor in subsequent logistic regression analysis [147].
A series of three papers from southern Sweden similarly reported on long-term symptoms of women after third-degree tears. Haadem et al surveyed patients two to seven years after delivery, and found that 28 of 59 (47%) had persistent symptoms: 15 with "incontinence for gas," 4 with "occasional incontinence for feces," 5 with dyspareunia, and 4 with perineal pain [148]. Compared to a control group without history of sphincter damage or other anorectal disease, these symptomatic women recorded a higher resting rectal pressure, a lower internal anal sphincter strength, a reduced ability to increase anal pressure, and less resistance to withdrawal of a rectal probe. No control patients, matched for age and parity, reported any of the symptoms mentioned above [149].
In their most recent research, Haadem et al began following women with anal sphincter rupture as soon as they were identified [150]. "Incontinence of gas" was reported at three months postpartum more frequently by the cases than by control patients, but pain and incontinence of urine and feces were not. Two of three manometric measures of anal sphincter function were lower in cases than in controls several days postpartum and again at three months. Although anal sphincter rupture patients showed modest recovery of objective sphincter function at three months, no further improvement occurred by one year postpartum.
In their hospital in Heerlen, the Netherlands, Go and Dunselman followed 20 patients with third-degree obstetric tears also involving the rectal mucosa (sometimes called fourth-degree lacerations) [151]. At six months postpartum, six patients still had anal incontinence (three with flatus, one with "semisolid feces," two with formed stools). Of the nine patients who consented to later follow-up, at a mean of 29 months postpartum, three continued to experience such symptoms, though by then none soiled with normal stools. Neither anal manometry nor EMG could reliably distinguish symptomatic from asymptomatic patients, though with such small numbers this result is not surprising. All values were in the "low to low normal range" established previously in normal subjects.
Crawford et al surveyed Michiganders nine to twelve months after their first deliveries [27]. Those who had experienced third-degree lacerations had persistent incontinence of flatus, but not liquid or solid stool, more often than those without this complication (odds ratio 7.03).
In stark contrast to these several studies, Venkatesh et al reported unusually low rates — 101/1040 (9.7%) — of any anorectal complications 12 to 72 months after third-degree episiotomy extensions [152]. However, they give no information about the completeness of their ascertainment methods, so their cases may represent only those voluntarily seeking treatment for their symptoms.
Møller Bek and Laurberg surveyed Danish women two to 13 years after delivery with third-degree tear [153]. About half experienced some degree of anal incontinence after this injury, usually transiently. Those who did had a 17% chance of developing permanent incontinence after a subsequent delivery, a risk nine times greater than those not noticing incontinence after the original injury. The authors concluded that although the symptoms attributable to sphincter damage normally resolve quickly (a finding contrary to those of several other studies discussed in this section), subclinical dysfunction lingers and can be exacerbated by subsequent deliveries in a cumulative and irreversible manner.
Surgical treatment of this problem is also perhaps less successful that has previously been thought. At St. Mark's Hospital in London, 20 patients with persistent anorectal incontinence had onset of symptoms shortly after a delivery involving anal sphincter division [94]. Of these, 60% also displayed EMG evidence of pudendal nerve damage. Snooks et al predicted that this subset of women would require extensive pelvic floor surgery, rather than simple sphincter repair, in order to regain continence. They confirmed this in a later paper; eight of ten patients without pudendal nerve damage had good or excellent results from sphincter repair, as opposed to only one of nine patients with co-existent nerve damage [154].
As noted in a recent review by Hordnes and Bergsjø, "Long term morbidity of severe laceration, especially anal incontinence, has in general been underestimated" [144].
Psychosocial consequences Over the last dozen years work has progressed on measuring the psychological and interpersonal sequelae of obstetric technology, which one writer has labeled "psychosocial morbidity" [155]. Though obviously more difficult to quantify, such effects are nevertheless both valid and important outcomes of our interventions. Most of the research in this area has been directed at assessing "satisfaction" with the birth experience.
A recent retrospective Australian survey found that use or non-use of episiotomy made no significant difference in the likelihood of a patient reporting "dissatisfaction" with her care in childbirth among parous patients, but its use more than doubled the rate of overall dissatisfaction in nulliparous women (odds ratio 2.26) [156]. However, many other confounding factors also affected this probability, and statistical adjustment to isolate the effect of episiotomy was not done.
In Cambridge, Green et al claimed that the use of any of several intrapartum interventions, including episiotomy, was negatively correlated with the patient's overall satisfaction with the birth experience [157]. They published no data from their research to substantiate this claim.
In Montreal, Séguin et al found no relationship between use of episiotomy and patient satisfaction [158]. Jacoby drew a similar conclusion from a survey of her French patients, although she added that among those women who had had a prenatal desire to avoid an episiotomy, satisfaction with the management of their labor was higher if none was performed [159].
Drew et al asked British women one to four days postpartum to rank 40 items by their importance to the patient's overall satisfaction with her care [160]. Interestingly, "Not having an episiotomy" ranked 37th, well below such items as the food being hot and having a "ward rest hour." In seeming contradiction, a German survey recorded that about 20% of women feel "disfigured" by the procedure [161].
Miscellaneous risks There continue to be occasional reports of rare but severe maternal and fetal complications of episiotomy. Most of these have not been studied systematically, but are, nevertheless, important considerations in assessing the overall risk/benefit ratio for this procedure. The following list is illustrative, not exhaustive:
Fetal risks Eyelid laceration [162]. Castration (in breech birth) [163]. Methemoglobinemia [164]. Lidocaine toxicity [165-166]. Increased rate of vertical transmission of HIV, at least in facilities where its use is not routine [167]. Maternal risks Extreme fear of subsequent delivery [168]. Intractable rectal hemorrhage [169]. Massive vulvar hematoma [170]. Necrotizing fasciitis [171]. Myonecrosis [172]. Relapsing toxic shock syndrome [173]. Brain abscess, seeded from an infected episiotomy site [174]. Hypersensitivity reactions, including anaphylactic shock, from latex contact during episiotomy repair [175]. Endometriosis arising in the episiotomy site [176-177]. (This has apparently never been reported in spontaneous laceration scars.) Granular cell tumor of the vulva in the episiotomy scar [178]. Clear cell carcinoma arising in the episiotomy site [179]. The episiotomy scar can become a site for metastasis of carcinomas, particularly of the cervix [180-181]. Risks to birth attendants Although not strictly a part of the risk-benefit analysis for the patient, it may be profitable briefly to mention risks assumed by practitioners in performing episiotomies.
Serrano et al demonstrated that, as might be expected, repair of a laceration or an episiotomy increases the risk of a glove perforation, usually by the suturing needle [182]. If, as asserted in section II.A.2.j. of this review, liberal use of episiotomy increases the number of patients requiring surgical repair, it then also increases the operator's exposure to blood-borne pathogens. In a study by Arena et al of 200 deliveries, the incidence of glove perforation during episiotomy repair was found to be 8%, half of which were unrecognized by the surgeon [183]. The increased overall blood loss resulting from episiotomy (section III.A. above) would also be expected to increase the chance of inadvertant exposure, even in the absence of needle injury.
There are legal risks as well. Contrary to what may be common belief among physicians, consent for episiotomy is not implied by a patient's presenting to the hospital for maternity care. "[A]n episiotomy performed without adequate consent is a serious offense and is an act which could open up the possibility of an action for heavy damages against those involved" [184]. Among United States malpractice suits related to colorectal disease, iatrogenic sphincter injuries constitute one of five major categories; about half of these are secondary to midline episiotomies [185].
Summary Mediolateral and, to a lesser degree, midline episiotomies substantially increase the amount of blood loss at delivery; in fact, simple avoidance of episiotomy may be the most powerful means the delivery attendant has to prevent excessive intrapartum hemorrhage. The long-term morbidity of the anal sphincter damage induced by episiotomy, particularly midline, has generally been underestimated in both its frequency and severity. Other potential fetal and maternal complications of episiotomies, though rare, are numerous and serious. The overall degree of risk that accompanies this procedure could only be justified by a clear and overriding benefit, which, as discussed in section II. of this review, does not appear to exist.
Conclusion If a study of the history of medicine reveals anything, it reveals that clinical judgment without the check of scientific controls is a highly fallible compass.
- Arthur Schafer [186]
As is perpetually the case in every scientific inquiry, our knowledge is partial and based on imperfect research. We always welcome new studies that increase the depth and breadth of our understanding. But we must make today's clinical decisions based on the best synthesis of the currently available information.
The English-language literature published since 1980 on the benefits and risks of episiotomy can be summarized as follows: Episiotomies prevent anterior perineal lacerations (which carry minimal morbidity), but fail to accomplish any of the other maternal or fetal benefits traditionally ascribed, including prevention of perineal damage and its sequelae, prevention of pelvic floor relaxation and its sequelae, and protection of the newborn from either intracranial hemorrhage or intrapartum asphyxia. In the process of affording this one small advantage, the incision substantially increases maternal blood loss, the average depth of posterior perineal injury, the risk of anal sphincter damage and its attendant long-term morbidity (at least for midline episiotomy), the risk of improper perineal wound healing, and the amount of pain in the first several postpartum days.
The most famous shibboleth of medicine, "Primum non nocere" ("First, do no harm") — that is, the assertion that the avoidance of inflicting any harm outweighs all other moral imperatives — probably has neither the historical nor the philosophical weight we tend to attribute to it [187-188]. Nevertheless, the principle of non-maleficence remains foundational to