Abstract
Whether levonorgestrel taken as an emergency contraceptive has an abortifacient effect is a matter of great importance for Catholic bioethics. While many have argued that LNG-EC does not have a postovulatory effect, a recent literature review has convincingly established that inhibition of ovulation cannot account for all of the pregnancy reduction observed in clinical settings among those who take LNG-EC. This essay proposes a secondary mechanism of action of LNG-EC that is postovulatory but prefertilization; it argues that LNG-EC may act in a contraceptive fashion by interfering with transport of the ovum to the site of fertilization in the timely fashion needed for reproductive success. While this mechanism of action cannot be established with the moral certitude required of these matters of life and death, further research may validate this mechanism beyond a reasonable doubt. National Catholic Bioethics Quarterly 14.2 : 235–244.
