Background:The rate of cesarean delivery has significantly increased in China in the last decade.Women with prior cesarean history tend to have a higher risk of uterine rupture during termination of the pregnancy in mid-trimester than those without such a history.The aim of our study was to evaluate the influences of the potential risk factors on uterine rupture in women with prior cesarean.Methods:We conducted this retrospective study of women with prior cesarean section,who underwent mid-trimester pregnancy termination between January 2006 and December 2013 in Peking Union Medical College Hospital.The protocol was oral administration ofmifepristone and misoprostol for the patients with the gestational ages below 16 weeks or intra-amniotic injection of ethacridine lactate (EL) for those with at least 16 weeks of gestational ages.The thickness of the lower uterine segment (LUS) was measured before the termination of pregnancy.Logistic regression was used to study the risk factors of uterine rupture.Results:The total rate of successful abortion was 93.9％ (62/66).Four patients failed in induction,and one of them received curettage,whereas the other three experienced uterine rupture (4.5％).The successful rates of abortion were 85.7％ (30/35) for women treated with mifepristone-misoprostol and 86.1％ (31/36) for those treated with EL.There was a significant difference in the mean LUS thickness between the uterine rupture group (3.0 ± 2.0 mm) and the nonrupture group (7.0 ± 3.0 mm) (P ＜ 0.05).The LUS thickness of＜3 mm was associated with uterine rupture during mid-trimester pregnancy termination in women with prior cesarean (odds ratio,94.0; 95％ confidence interval 4.2-2106.1) after adjusted matal age,gestational age,interdelivery interval and prior cesarean section.Severe bleeding that required transfusion occurred in one case (1.5％).Conclusions:Both the mifepristone-misoprostol and the EL regimens were effective and safe for the termination of mid-trimester pregnancy in women with prior cesarean.A thinner LUS is associated with a relatively high risk of uterine rupture.