Effect of previous live birth and prior route of delivery on the outcome of early medical abortion.

Objective: To determine the association between type of previous delivery (vaginal compared with cesarean) on the success of medical abortion with mifepristone-misoprostol in early pregnancy.

Methods: The records of 879 women with intrauterine pregnancies at or before 56 days of gestation who underwent medical abortions were reviewed. Medical treatment consisted of 600 mg mifepristone orally followed 48 hours later with oral misoprostol. An ultrasound examination was performed 14-21 days after treatment, and a successful medical abortion was defined as an empty uterus without surgical intervention. Univariable and multivariable logistic regressions were used to determine risk factors for failure of medical abortion.

Results: A total of 797 (90.7%) women had successful medical abortions; 82 (9.3%) had failed medical abortions. Multivariable logistic regression indicated that women with gestational ages greater than 42 days (odds ratio [OR] 2.53, 95% confidence interval [CI] 1.55-4.05) had higher odds of failed abortion compared with a gestational age less than 43 days. Parous women (OR> or =3.94, 95% CI 1.83-8.53) and those with prior cesarean delivery (OR 9.59, 95% CI 4.30-21.39) were more likely to have failed abortions compared with nulliparous women. Among 523 parous women (68 had failed abortion), those with gestational ages greater than 42 days (OR 2.07, 95% CI 1.22-3.50) and prior cesarean delivery (OR 3.33, 95% CI 1.95-5.69) were more likely to have failed abortions compared with those with gestational ages less than 43 days or with prior vaginal delivery.

Conclusion: Parous women are at increased risk for failed medical abortion in comparison with nulliparous women. Prior cesarean delivery is significantly associated with failed medical abortion.