Medical abortion regimens: historical context and overview.

Medical abortion offers an important alternative to surgical abortion for women with early pregnancies who wish to avoid a surgical procedure. More than 3 million women worldwide have had medical abortions in the past decade alone. The best-studied regimens include mifepristone orally followed 36 to 48 hours later by a prostaglandin analog administered either orally or intravaginally. Because of political and social restrictions related to mifepristone, however, researchers have investigated alternative regimens, most notably methotrexate and misoprostol. Mifepristone regimens are approximately 95% effective for abortion at </=49 days' gestation. Efficacy between 50 and 63 days' gestation varies according to the type and route of administration of the prostaglandin analog. Complete abortion rates among these later gestations are clinically acceptable when mifepristone is followed by intravaginally administered misoprostol or gemeprost. This report reviews the development, efficacy, and side effects of mifepristone regimens.