BACKGROUND: Termination of pregnancy is an important and necessary back-up method for family planning services in many countries. The combination of mifepristone and misoprostol is a widely used alternative to surgical evacuation of the uterus in early pregnancy; however, there are few reports about medical abortion in women with a prior uterine incision and few studies have described curettage occurring as part of the procedure and an indication for the intervention. Curettage in a prior uterine incision can increase operative complications. The purpose of this study was to investigate whether vaginal bleeding intervals, routine ultrasound scan and serum beta-hCG test after medical abortion could accurately identify women with uterine scars who would require curettage. METHODS: Six hundred sixty-eight women with a uterine scar and at up to 49 days of gestation underwent a medical abortion with mifepristone and misoprostol. Each woman took 50 mg and 25 mg of mifepristone orally in the morning and in the evening, respectively, for 2 days and 600 mcg of misoprostol orally on the third day. RESULTS: Of the 668 women, 6 (0.9%) were lost to follow-up. The overall complete abortion rate was 91.7%; 55 women underwent curettage, including 2 women with heavy bleeding, 3 women with ongoing pregnancy and 34 women with incomplete abortion. The incomplete abortion rate was significantly greater in women with persistent bleeding lasting 21 days than in women with persistent bleeding lasting 14 days (p<.001), and the overall sensitivity and specificity of vaginal bleeding interval (21 days) were 97.1% and 75%, respectively. The incomplete abortion rate was also greater in women whose serum beta-hCG was >or=500 IU/L than in women whose serum beta-hCG was <500 IU/L (p<.001), and the overall sensitivity and specificity of serum beta-hCG (>or=500 IU/L) were 97.1% and 62.5%, respectively. Moreover, the incomplete abortion rate was greater in women with an endometrial thickness >or=15 mm than in women with an endometrial thickness <15 mm (p<.001), and the overall sensitivity and specificity of endometrial thickness (>or=15 mm) were 94.1% and 75%, respectively. No complication occurred. CONCLUSIONS: The combination of mifepristone and misoprostol was found to be a safe and effective method to terminate early pregnancy in women with a previous cesarean delivery. If a woman with a prior uterine incision experienced vaginal bleeding intervals >or=21 days and/or had a bilayer endometrial thickness >or=15 mm and/or serum beta-hCG >or=500 IU/L after a medical abortion, then she should undergo curettage.