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Rhythm method criticised as a killer of embryos
00:01 25 May 2006 by Alison Motluk
The range of birth control choices may have become narrower for couples that believe the sanctity of life begins when sperm meets egg. The rhythm method, a philosopher claims, may compromise millions of embryos.
"Even a policy of practising condom usage and having an abortion in case of failure would cause less embryonic deaths than the rhythm method," writes Luc Bovens, of the London School of Economics, in the Journal of Medical Ethics.
With other methods of contraception banned by the Catholic church, the rhythm method has been one of the few options available to millions.
In using the rhythm method, couples avoid pregnancy by refraining from sex during a woman's fertile period. Perfect adherents claim it is over 90% effective - i.e. one couple in 10 will conceive in an average year. But, typically speaking, effectiveness is estimated at closer to 75%.
Now Bovens suggests that for those concerned about embryo loss, the rhythm method may be a bad idea. He argues that, because couples are having sex on the fringes of the fertile period, they are more likely to conceive embryos that are incapable of surviving.
Fertile window
As many as 50% of conceptions may not survive long enough even to disrupt menstruation, Bovens says. It is reasonable to assume then, he adds, that embryos created from sperm that has been sitting for days within the female's reproductive tract before ovulation may be disadvantaged.
The situation is similar, he suggests, for eggs that have been waiting around for sperm to arrive. These are the only two likely scenarios where fertilisation might occur using the rhythm method, he points out.
These embryos may then face a less-than-ideal uterine lining, he points out, since the uterus is not as receptive outside of the most fertile period.
Bovens calculates that, if the rhythm method is 90% effective, and if conceptions outside the fertile period are about twice as likely to fail as to survive, then "millions of rhythm method cycles per year globally depend for their success on massive embryonic death".
Pill under fire
Other birth control methods also fail the test in terms of preventing embryo death. The morning-after-pill, for instance, affects the uterine lining, so will prevent an embryo from implanting in the uterine wall.
Even the birth control pill has recently come under fire, since one of the ways it prevents pregnancy is by thinning the uterine lining, again making implantation unlikely.
Randy Alcorn, a pro-lifer and Christian minister in Gresham, Oregon, US, recently stated that "even an infinitesimally low portion - say, one hundredth of 1% - of 780 million pill cycles per year globally could represent tens of thousands of unborn children lost to this form of chemical abortion".
Fertile fringes
"If you're concerned about embryonic death," Bovens says, "you've got to be consistent here and give up the rhythm method."
Roger Gosden, at the Center for Reproductive Medicine and Infertility in New York, US, says: "It's quite plausible that more abnormal embryos are conceived at the limits of sperm - and especially egg - viability," he says, "and that these are more frequent in women practising rhythm contraception than those having unprotected intercourse at random stages of the menstrual cycle."
He recalls that at least one study found that Roman Catholics had higher rates of miscarriage, presumably, he says, due to aged gametes. "Actually confirming this is not easy, though," he admits.
Paul Tully, general secretary for the Society for the Protection of Unborn Children in London, UK, says this may cause concern to users of natural family planning. "It may lead to adjustment in the way they use it," he says. "But I don't think it will undermine the whole technique."
Journal reference: Journal of Medical Ethics (vol 32, p 355).
