Factors affecting the outcome of early medical abortion: a review of 4132 consecutive cases

Objective To assess the outcome of a regimen of a reduced dose of mifepristone followed by one or two doses of vaginal misoprostol as a non-surgical method for termination of pregnancy.

Design Prospective observational study.

Setting Aberdeen Royal Infirmary, Aberdeen, Scotland.

Population Women seeking abortion under the 1967 Abortion Act.

Methods Factors influencing the outcome in a consecutive series of 4132 women undergoing early medical abortion in one Scottish teaching hospital since 1994.

Main outcome measures Complete abortion rates following one or two doses of misoprostol. The effect of age, gestation, previous pregnancy and previous termination on complete abortion rates following the medical regimen.

Results Of the 4132 women, 95 (2.3%) aborted within 48 hours of mifepristone and a further 3942 (95.4%) achieved complete abortion following administration of one or two doses of misoprostol. Thus, the overall complete abortion rate was 97.7% (4037/4131). A total of 94 (2.3%) women required surgical intervention of whom 13 (0.3%) had a continuing pregnancy. Following change of the regimen to include the possibility of two doses of misoprostol the continuing pregnancy rates were significantly reduced (OR = 5.88) and gestation ceased to have an effect on overall efficacy. Women who had a previous abortion were more likely to have a failed medical abortion (OR = 2.09), while women with no previous termination, but a previous live birth were more likely to have a failed abortion (OR = 2.03).

Conclusion Mifepristone in combination with one to two doses of vaginal misoprostol is an effective regimen for early medical abortion. The option of administering two doses of misoprostol significantly reduced the ongoing pregnancy rates and abolished the effect of gestation on overall efficacy. Previous termination was the strongest predictor of failed medical abortion.