Does NFP Lead to “Massive Embryonic Death”?

FertilizationUh, no. But that’s precisely what Luc Bovens would have us believe. Bovens is a professor at the London School of Economics and Political Science who recently wrote an article titled “The Rhythm Method and Embryonic Death”, which appeared in the British Medical Journal‘s subsidiary, the Journal of Medical Ethics. In the article, Bovens writes:

What has gone unnoticed is that, if one is willing to make a few relatively innocent assumptions, then the rhythm method may well be responsible for massive embryonic death and the same logic that turned pro-lifers away from morning after pills, IUDs and pill usage, should also make them nervous about the rhythm method.

Here, Bovens makes an all-too-common mistake: he equates natural family planning (NFP) with the “(calendar) rhythm method”–which is obsolete, and has been for decades. Aside from ecological breastfeeding, the two most common forms of NFP now used by couples are the Sympto-Thermal Method and the Billings Ovulation Method, both of which are vastly different–and far more scientifically sound–than calendar rhythm. Bovens goes on to state his assumptions:

The first assumption is that there are a great number of conceptions that never result in missed menses. There are estimates that only 50% of conceptions actually lead to pregnancies. The second assumption is that, even in clinical trials, the rhythm method can fail due to the fact that a pregnancy results from sexual intercourse on the last days before and the first days after the prescribed abstinence period. Estimates of the effectiveness of the rhythm method vary in the literature, but let us set its effectiveness for clinical trials at 90%—that is, conscientious rhythm method users can expect one pregnancy in ten woman years. The third assumption is that there is a greater chance that a conception will lead to a viable embryo if it occurs in the centre interval of the fertile period than if it occurs on the tail ends of the fertile period. This assumption is not backed up by empirical evidence, but does have a certain plausibility. From assumption one, we know that there is a high embryonic death rate. It seems reasonable to assume that an embryo that results from an “old” ovum (that is waiting at the end of the fertile period) or an “old” sperm (that is still lingering on from before ovulation), and that is trying to implant in a uterine wall that is not at its peak of receptivity, is less viable than an embryo that comes about in the centre interval of the fertile period. Let us make a conservative guess that the chance that an embryo conceived in the centre interval of the fertile period, which coincides with the abstinence period in the rhythm method—let us call this “the heightened fertility (HF) period”—is twice as likely to be viable as an embryo conceived at the tail ends of the fertile period.

Bovens then proceeds to make his case that “millions of rhythm method cycles per year globally depend for their success on massive embryonic death.” In a series of letters published on the Journal of Medical Ethics’ website, Bovens’ article gets the scientific smackdown it deserves. Dr. Mark Whitty demolishes Boven’s “assumptions”–and, in the process, presents some key lessons about human reproduction:

[Bovens’] first assumption that 50% of natural human conceptions are lost is an often-repeated figure based on problematic research in 1956 (1) using histological anaysis of hysterectomies where intercourse was encouraged prior to surgery. The higher figure of 78% often quoted rests on a 1975 analysis (2) of an hypothesis based on a series of weak assumptions. Animal studies commonly give percentages in single figures. Boven’s third assumption is wholly invalid in the light of current knowledge of human reproductive physiology. The ovum lasts for about 12 hours, 24 at most; sperm may last up to 3-5 days with the support of both the appropriate types of cervical mucus and of the activity of the cervical crypts. Any conception is as viable as the next, barring a fatal genetic or developmental defect; there is no truth to the old “old sperm” or “old ovum” speculation, or its “twice as likely to be viable”, “lack resilience” and “reduced survival chances” assumption. Neither is there any truth in the “heightened fertility (HF)” and ‘tail- end fertility” idea, with or without further speculative assumptions about extrapolated comparative embryonic viability based on this innacuracy. A luteal phase of less than 11 days may be insufficient to sustain a natural conception, but this is a case for medical intervention. So all that follows based on the HF and other assumptions is invalid. His fourth point of counter-argument depends on the idea that natural conception could be timed in NFP use for when the endometrium is inhospitable to an embryo; this is physiological nonsense. The symphony of ovulation-related events ensures that the endometrium is ready for implantation until when either the corpus lutem expires or ßHCG is produced. It is a complete fallacy to assert, even in regard to the obsolete rhythm method, that any NFP methods “depend for their successes on massive embryonic death”.

Whitty notes another major flaw in Bovens’ article:

The article fails to acknowledge the distinction between natural loss and loss caused by deliberate human intervention; common sense and every criminal law system recognise the importance of knowledge and intent in human responsibility; in particular, the fact that accidental deaths happen does not justify causing similar deaths.

In other words, there is no moral comparison between NFP and artificial contraception. Not surprisingly, this distinction was lost on major international newspapers who proved to be willing buyers of Bovens’ bill of goods:

What is perhaps most interesting about the uncritical reaction by members of the mainstream media to Bovens’ article is that his background is in philosophy and sociology–not in biology, medicine, or any of the “hard sciences”. It’s especially ironic considering how often these same mainstream media portray pro-lifers–especially those of us who oppose contraception–as a gaggle of slack-jawed, unsophisticated, anti-scientific bumpkins.

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