Reevaluating the Efficacy of Medical Abortion

Allison A. Hedley, Princeton University
Charlotte Ellertson, Population Council
Abigail Norris Turner, Population Council
James Trussell, Princeton University

We propose a new standard method for evaluating the efficacy of medical abortion. Previous research on the efficacy of medical abortion has followed the conceptual model for the analysis of surgical abortion; the failure rate is computed by simple division and expressed as a proportion. While this method of calculating efficacy is appropriate for the discrete event of surgical abortion, it is inappropriate for medical abortion because it fails to account for the temporal process of medical abortion and allows for only one type of failure. We assert that the conceptual model used to calculate contraceptive efficacy is more appropriate because: 1) Life table procedures incorporate the important dimension of time in success and 2) Both method and elective failures are calculated. Using data on more than 6,500 women from 6 previously conducted medical abortion studies, we use life table procedures to reevaluate the efficacy of medical abortion.