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Re: Risk of 2nd trimester amniocentesisFrom: The-Hung Bui (The-Hung.Bui@ks.se)Mon May 21 06:09:12 2001
At 19:32 2001-05-18 -0500, you wrote: >When talking to patients, what risk of 2nd trimester amniocentesis do >you mention? I think the usual is 1/200 to 1/300, although it is not >clear to me if that is the risk of fetal loss, or just the risk of >"something" happening. > >Joseph A Worrall MD RDMS >Fairbanks, Alaska The only randomized study comparing second trimester genetic amniocentesis vs no procedure is the Danish study of Tabor et al (Lancet 1986;i:1287-93). Re-analysing it, the fetal loss rate due to amniocentesis is 0.9% (95% CI, 0.0--1.9) and the mid-range interval (25th--75th percentile) can be estimated to 0.6--1.2%. Fetal loss were taken as any losses after randomization (i.e. including all spontaneous losses, terminations, stillbirths and neonatal deaths). This methods will overestimates the absolute risk of procedure-related fetal losses but avoids making assumptions about the miscarriage rate of fetus with an abnormality; the difference in fetal loss rate between the randomized groups is an unbiased estimate of the risk associated with the more hazardous procedure (amniocentesis). In the control group, the number of infants born alive with a chromosomal abnormality or NTD was added to the fetal losses because affected pregnancies in the study group were detected and terminated. This Danish study covered the period 1982-1984. Improvement in technique and equipment over time may therefore mean that efficacy and safety have improved. For example, it is widely perceived by clinicians that the fetal loss rate following second trimester amniocentesis (after 14 wk GA) is lower than 0.9%. The lower 95% CI is 0.0%; thus, a lower risk is quite possible. Without full and unbiased data the uncertainty will remain. It is up to those claiming a (significantly) lower risk to fully report their series, indeed ethical considerations dictate that they do just that instead of argumenting from data unavailable to the rest of the scientific and clinical community. ***************************************************************** The-Hung Bui, M.D. Senior Consultant -- Director, Fetal Diagnosis Programme Department of Molecular Medicine Clinical Genetics Unit Karolinska Hospital S-171 76 Stockholm, Sweden
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