In the spring 2008 issue of HCEUSA (see "Ethical Currents," pp. 12-13), we provided an update on the controversy over emergency contraception. Among other things, we noted an update article by priest, theologian and scientist, Fr. Nicanor Pier Austriaco, on the mechanism of action of levenorgestrel (LNG) or Plan B (National Catholic Bioethics Quarterly 7 (Winter 2007): 703-707). After reviewing the scientific literature, Fr. Austriaco came to the conclusion that the "studies published in the past few months provide mounting evidence that levenorgestrel has little or no effect on post-fertilization events" (p. 707).

In the most recent issue of the same journal (National Catholic Bioethics Quarterly [Autumn 2008]: 418-425), Fr. Austriaco published another article in which he replies to his critics. Readers of this column are referred to the entire article. Here we report only Fr. Austriaco's conclusions.

If Plan B is abortifacient, the author observes, it can have this effect in three primary ways. The first is by increasing the rate of ectopic pregnancies. However, he notes that the"combined data from five clinical trials with nearly six thousand women showed that the rate of ectopic pregnancies in women who have used Plan B is 1.02 percent as compared to the overall national ectopic pregnancy rate between 1.24 percent and 1.97 percent. In light of this finding, it is unlikey that Plan B increases the ectopic pregnancy rate …" (p. 422).

The second way in which Plan B could be abortifacient is by preventing implantation of an embryo. This can occur by altering the lining of the endometrium, making it inhospitable to implantation. "[M]orphological and biochemical analyses of endometrial biopsies of women who had taken Plan B eight or nine days prior to the biopsy have revealed that the drug does not dramatically alter the structures of this tissue.This suggests that the drug does not compromise endometrial development" (p. 422).

It could also occur by disrupting the function of the corpus luteum which releases hormones that are necessary for the proper development of the endometrium, including making it receptive to an embryo. After reviewing the scientific literature, Fr. Austriaco concludes that "[T]ogether, these data suggest that the risk of a post-fertilization effect from this mode of action for any particular individual woman, if it is real, would be vanishingly small" (p. 423).

Or, it could occur by directly interfering with the implantation process itself. Fr. Austriaco replies: "[O]ne study that directly tested the ability of human embryos to implant on endometrial tissue exposed to LNG — though grossly immoral — does not support this mode of action for Plan B" (p. 423). Two other more recent studies confirm this conclusion.

A third way in which Plan B could be abortifacient is by destroying an already implanted embryo. With regard to this possibility, Fr. Austriaco says: "[A] report from the FDA shows that Plan B does not increase the rate of pregnancy loss or the frequency of fetal abnormalities once a pregnancy has been established" (p. 423).

Fr. Austriaco concludes his article: "[I] stand by my earlier conclusion: In light of the available scientific evidence and given the inherent limitations of the studies, it is unlikely that Plan B is an abortifacient" (p. 424).

— R.H.

 

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