Abstract: Mifepristone combined with misoprostol has been widely applied in medical abortion for terminating first trimester pregnancy due to its effectiveness, safety and acceptability. However, there are some unfavourable problems, such as incomplete abortion and ongoing pregnancy. Several factors have been found to be related to the clinical outcomes of medical abortion, such as single misoprostol, the insufficient dose of mifepristone or misoprostol, the short interval time of two medicines, oral administration of misoprostol, the increased pregnancy time, the oversized pregnancy sac diameter, the multiple parous history, the history of cesarean section, the uterine anteflexion or retroflexion and the inappropriate intervention. Those factors related to the outcomes of medical abortion, as well as the mechanism, are discussed in this review, which is helpful for the clinic to improve the effectiveness and safety of medical abortion.

Key words: Mifepristone, Misoprostol, Pregnancy trimester, first, Abortion, induced