--
A Philosopher's Take on the Rhythm Method Is Rattling Opponents of Abortion
The Rhythm Method and Embryonic Death
(Journal of Medical Ethics) Luc Bovens, a philosopher at the London School of
Economics, argues in the Journal of Medical Ethics that couples who try to
prevent pregnancy by avoiding sex during the woman's most fertile time of month
may be more likely to produce embryos that do not develop or implant in the
womb.
If this is correct, he writes, then "millions of rhythm method cycles per year
globally depend for their success on massive embryonic death."
Those who worry about early embryonic death should be as concerned about the
rhythm method as they are about other forms of contraception, like Plan B, and
about embryonic stem cell research, he asserts.
Dr. Bovens's article has drawn swift response from abortion opponents in the
United States and the United Kingdom, many of whom are proponents of natural
family planning, an outgrowth of what was once called the rhythm method.
These critics have taken aim at Dr. Bovens's analogy between early embryonic
deaths that may occur because of the timing of intercourse and losses that may
result from the use of contraception. They have also questioned the assumption
that embryos conceived on the fringe of a woman's fertile window are less
likely to be viable.
Fertility experts say that there is little evidence to support this assumption
but that there are some indications it may be valid.
Dr. Bovens uses the term rhythm method to refer to any approach that allows
couples to predict the woman's most fertile time of month, so that they can
abstain from sex during that time. Traditionally, the term referred more
narrowly to a strategy of counting calendar days from the woman's menstrual
period, to estimate ovulation.
Natural family planning is the more widely used, contemporary term for the broad
range of techniques aimed at helping women to predict fertile days so they can
avoid having sex then. These techniques may rely on cues like the presence of
cervical mucus or small changes in body temperature, which occur around the
time of ovulation. Dr. Bovens notes that some couples choose this approach
because they worry that other forms of contraception, like birth control pills,
may act in part by preventing an early embryo from implanting in the womb.
However, if a fertilized egg produced on the fringe of the fertile window is
less likely to develop and implant, he writes, "the same logic that turned
pro-lifers away from morning after pills, I.U.D.'s and pill usage should make
them nervous about the rhythm method."
Dr. Bovens also contends that opponents of abortion ought to favor barrier
methods, like condoms, because these are likely to cause fewer embryonic
deaths. "Even a policy of practicing condom usage and having an abortion in
case of failure would cause less embryonic deaths than the rhythm method," he
writes.
Joseph B. Stanford, an associate professor at the University of Utah School of
Medicine who is against abortion, said Dr. Bovens's reasoning was flawed.
There is a difference, he argued, between forming an embryo that is not viable —
which may occur for couples using any form of family planning, including natural
family planning — and taking an action, like using emergency contraception or
birth control pills, that could prevent a viable embryo from developing. "For
me, it's sort of like the difference between a miscarriage and an induced
abortion," he said.
Dr. Stanford and other critics also question Dr. Bovens's central assumption,
that embryos formed outside of a woman's most fertile period are less likely to
be viable. Fertility experts, too, say there is little direct evidence to
support this assumption, though some believe it is possible.
Roger G. Gosden, professor of reproductive medicine in obstetrics and gynecology
at the Weill Medical College of Cornell University, said there were no "really
solid studies demonstrating that the time of conception is related to the
probability of conceiving a healthy conceptus."
But, he added, "there are numerous indications that this is the case."
A woman is most likely to become pregnant if she has sex close to the time of
ovulation, and especially during the two to three days before the egg is
released from the ovary. The egg is viable for only about 24 hours after
ovulation. And if it is fertilized toward the end of that period, it is less
likely to develop, possibly because of chromosomal errors, Dr. Gosden said.
More specifically, he added, there is evidence that when an egg lingers in the
reproductive tract, the cell's spindle apparatus, which holds the chromosomes,
may weaken, causing the chromosomes to fall off. This may increase the
likelihood of an abnormal chromosome number, should fertilization occur.
In addition, there is an optimal window for implantation, roughly seven days
after ovulation, Dr. Gosden said. Outside of this window, implantation is
unlikely to occur, probably because of changes in the receptivity of the lining
of the uterus.
"Life is very tentative in its early, tender stages. It takes on a whole
different significance and security" later on, he said.
Fertility experts also cite work by Allen J. Wilcox of the National Institute of
Environmental Health Sciences as evidence that when conception occurs at the
later end of the woman's fertile period there may be an increased risk of
embryonic loss.
In a 1998 article published in Human Reproduction, Dr. Wilcox found that the
loss of early embryos increased as the eggs got older.
In an e-mail message, Dr. Wilcox said, "While our result is preliminary, the
risk of pregnancy loss does seem to be highest on the last fertile day of the
cycle."
He added, "And it stands to reason that, if couples abstaining through their
fertile days make a mistake, they are more likely to have intercourse on that
last fertile day than on earlier days."
The effectiveness of natural family planning techniques is said to range from
greater than 90 percent for perfect practice to roughly 75 percent for typical
practice. If implantation occurs, the users of natural family planning do not
appear to be at higher risk of spontaneous abortion (or miscarriage).
Ronald H. Gray of the Johns Hopkins Bloomberg School of Public Health called the
evidence on this point "a mixed bag."
In a 1995 study in the American Journal of Obstetrics and Gynecology, Dr. Gray
found that women with a history of miscarriage and who had had "a conception
distant from the day of ovulation" were more likely to have a pregnancy loss.
But, the same did not seem to be true for women with no history of miscarriage.
John Harris, editor of the Journal of Medical Ethics, said it was not clear
whether Dr. Bovens's empirical assumptions were correct. But he said he hoped
the article would foster debate. Our "whole attitude to the embryo is
inconsistent and needs to be rethought," he said.
Roughly 50 percent of naturally occurring conceptions do not result in
implantation or a viable pregnancy, experts say. In many cases, the loss occurs
so early that a woman has her period on schedule and does not even know that she
has conceived.
But Judie Brown, president of the American Life League, said that these issues
were beside the point.
Pregnancy, she said, is "a very natural process and so is the natural selective
process that our body goes through to eliminate, for whatever reason, an embryo
during the first few days of life."
"There is nothing bad about that," she said. "There is nothing even to be
debated about that. That is the way nature works."
