The rhythm method and embryonic death
- Correspondence to: L Bovens London School of Economics and Political Science, Department of Philosophy, Logic, and Scientific Method, Houghton Street, London WC2A 2AE, UK;
- Received 9 August 2005
- Accepted 11 August 2005
Some proponents of the pro-life movement argue against morning after pills, IUDs, and contraceptive pills on grounds of a concern for causing embryonic death. What has gone unnoticed, however, is that the pro-life line of argumentation can be extended to the rhythm method of contraception as well. Given certain plausible empirical assumptions, the rhythm method may well be responsible for a much higher number of embryonic deaths than some other contraceptive techniques.
↵i By the probability calculus, the probability of viability (p) equals the conditional probability of viability given that the conception occurred outside the HF period (q) times the probability that the conception occurred outside the HF period (r) plus the conditional probability of viability given that the conception occurred during the HF period (2q) times the probability that the conception occurred during the HF period (1-r). Hence, p = qr + 2q(1-r). We set p = 1/2 by assumption one and let r ε [1/10, 1/3]. Hence q ε [10/38, 3/10] ≈ [1/4, 1/3].
↵ii John Harris makes a similar argument for procreation.2 If one is genuinely concerned about embryonic death, then one should choose reproductive techniques that minimise embryonic death. If IVF had developed to the point that a pregnancy could be brought about at minimal cost of embryonic death, then one would be required to refrain from reproducing through sexual intercourse, because it would come at a needlessly high cost of embryonic death. Harris (Harris,2 p 346) takes this to be a reductio ad absurdum of the reverence with which the pro-life movement treats embryos in the discussion about stem cell research.