OBJECTIVE: Our purpose was to determine whether a prior cesarean delivery affects the incidence of complications in women having an indicated midtrimester medical pregnancy termination. STUDY DESIGN: A retrospective review of women who underwent a midtrimester medical termination of pregnancy from January 1980 to July 1995 ascertained obstetric history, uterotonic agent(s), and the occurrence of uterine rupture, blood transfusion, or curettage. The frequencies of maternal complications were compared in women with and without a prior cesarean section. RESULTS: Our study population included 606 women with a mean gestational age of 21.1 ± 3.1 weeks and a mean maternal age of 26.3 ± 7 years. Seventy-nine (13%) had undergone a prior cesarean section. There was no significant difference in the need for curettage between women with and without a prior cesarean section. However, there was an increased need for blood transfusions in women with a prior cesarean delivery (11.4% vs 5.3%, odds ratio 2.3, 95% confidence interval 1.1 to 5.0, p = 0.04). The incidence of uterine rupture was significantly higher among women with a prior cesarean (3.8% vs 0.2%, odds ratio 20.8, 95% confidence interval 14.1 to 104, p = 0.008). CONCLUSION: Our data suggest that a prior cesarean section is a risk factor for uterine rupture and blood transfusion in women having a midtrimester pregnancy termination.