To evaluate the effects of prior single-layer compared with double-layer closure on the risk of uterine rupture.A multicenter, case-control study was performed on women with a single, prior, low-transverse cesarean who experienced complete uterine rupture during a trial of labor. For each case, three women who underwent a trial of labor without uterine rupture after a prior low-transverse cesarean delivery were selected as control participants. Risk factors such as prior uterine closure, suture material, diabetes, prior vaginal delivery, labor induction, cervical ripening, birth weight, prostaglandin use, maternal age, gestational age, and interdelivery interval were compared between groups. Conditional logistic regression analyses were conducted.Ninety-six cases of uterine rupture, including 28 with adverse neonatal outcome, and 288 control participants were assessed. The rate of single-layer closure was 36% (35 of 96) in the case group and 20% (58 of 288) in the control group (P<.01). In multivariable analysis, single-layer closure (odds ratio [OR] 2.69; 95% confidence interval [CI] 1.37-5.28) and birth weight greater than 3,500 g (OR 2.03; 95% CI 1.21-3.38) were linked with increased rates of uterine rupture, whereas prior vaginal birth was a protective factor (OR 0.47; 95% CI 0.24-0.93). Single-layer closure was also related to uterine rupture associated with adverse neonatal outcome (OR 2.89; 95% CI 1.01-8.27).Prior single-layer closure carries more than twice the risk of uterine rupture compared with double-layer closure. Single-layer closure should be avoided in women who could contemplate future vaginal birth after cesarean delivery.II.