Rhythm method criticized as a killer of embryos
New Scientist, 25 May 2006
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.
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
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 windowAs 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.
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.
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.
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 fireOther
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.
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."
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).