The rhythm method - the only form of contraception approved by the Catholic Church - may actually be the source of mass-scale embryo carnage.
Or so at least says Luc Bovens, a professor of philosophy at the London School of Economics.
Part of Catholics' opposition to the contraceptive pill, he points out, is that it in the event that a woman ovulates despite it and the egg is fertilised, then the pill's effect on the lining of the uterus may prevent the resulting embrryo from implanting. Since, according to Church doctrine, life begins at fertilisation then that can technically be interpreted as an abortion. Ditto for the intrauterine device (IUD).
In natural menstrual cycles, free from hormonal or pharmaceutical or mechanical manipulation, there is an optimal time of conception - within a day or two of the egg being released from the ovary. Leave them too long and they start to pass their prime, less able to carry the genetic recipe for a healthy baby.
So, Bovens says in the Journal of Medical Ethics, it's reasonable to assume that some of the rhythm method's effectiveness comes not from preventing the egg and sperm getting together in the first place, but from the creation of runt embryos that don't stand a chance of passing muster in the great Darwinian survival race. Add a decaying uterus lining later in the cycle and the poor clump of cells doesn't stand a snowball's.
The same argument could apply to a newly released egg that is fertilised by geriatric sperm, still hanging around from before the period of abstinence.
"If it is callous to use a technique that makes embryonic death likely by making the uterine wall inhospitable to implantation," Bovens writes, "then clearly it is callous to use a technique that makes embryonic death likely by organising one's sex life so that [fertilised] ova lack resilience and will face a uterine wall inhospitable to implantation."
It might be possible to draw a divide, he says, between deliberate, active abortion and accepting that the loss of an embryo is one of a range of possible actions of a form of contraception.
"There may indeed be a psychological distinction, similar to the comfort a person in a firing squad receives from not knowing that it was his bullet that killed the victim," Bovens sniffs. "But I do not think that this argument has any normative force."
On the other hand, he concludes, fretting about the question at all could be seen as, "a reductio ad absurdam of the cornerstone of the argument of the pro-life movement, namely that the deaths of early embryos are a matter of grave concern."
