Association between ultrasonographic parameters of Cesarean scar defect and outcome of early termination of pregnancy

Objective To determine whether Cesarean scar defect (CSD) parameters assessed by transvaginal sonography (TVS) might affect the outcome of early termination of pregnancy (TOP) with mifepristone-misoprostol. Methods This was a retrospective review of 183 women with previous Cesarean delivery who received oral mifepristone and misoprostol for TOP. A successful TOP was defined by the absence of an intrauterine gestational sac, with no need for surgical intervention. CSD was diagnosed by TVS in the presence of a hypoechogenic indentation within the myometrium of the lower uterine segment at the site of a previous Cesarean incision. Women were analyzed in three subgroups according to size of defect (ratio of residual myometrial thickness over the defect to adjacent myometrial thickness < 30%, 30%-70% and > 70%). Results Of the 183 women, 43 (23.5%) had failure of TOP. Fifty-nine (32.2%) had CSD detectable at TVS, and these women had a higher failure rate of TOP than did those without CSD (38.9% vs 16.1%; P = 0.001). CSD was associated significantly with failure of TOP (odds ratio, 3.32 (95% CI, 1.64-6.75)). The TOP failure rates in relation to defect size in the myometrial thickness ratio < 30%, 30%-70% and > 70% subgroups were 57.1%, 25.0% and 18.2%, respectively. There was a linear trend in failure rate across these ratios (Cochran-Armitage trend test; P = 0.015). Conclusions Women with CSD are at increased risk of failed TOP. Women with a defect in which the residual myometrial thickness was < 30% of the adjacent myometrial thickness tended to have a greater chance of failed TOP. CSD detected at TVS is of clinical relevance in counseling women with a history of Cesarean delivery who are considering TOP.