Uterine rupture risk in a trial of labor after cesarean section with and without previous vaginal births

Purpose: Previous cesarean delivery (CD) is the main risk factor for uterine rupture when attempting a trial of labor. Previous vaginal delivery (PVD) is a predictor for the trial of labor after cesarean (TOLAC) success and a protective factor against uterine rupture. We aimed to assess the magnitude of PVD as a protective factor from uterine rupture. Methods: A retrospective cohort study was conducted, including women who underwent TOLACs from 2003 to 2015. Women with and without PVD were compared. Inclusion criteria were one previous CD, trial of labor at ≥ 24 weeks’ gestation, and cephalic presentation. We excluded pre-labor intrauterine fetal death and fetal anomalies. The primary outcome was a uterine rupture. Secondary outcomes were maternal and fetal complications. Logistic regression modeling was applied to analyze the association between PVD and uterine rupture while controlling for confounders. Results: A total of 11,235 women were included, 6795 of which had a PVD. Women with PVD had significantly lower rates of uterine rupture (0.18% vs. 1.1%; OR 0.19, p < 0.001), were less likely to be delivered by an emergency CD (13.2% vs. 39.4%, OR 0.17, p < 0.0001), were more likely to undergo labor induction (OR 1.56, p < 0.0001), and were less likely to undergo an instrumental delivery (OR 0.14, p < 0.001). Logistic regression modeling revealed that PVD was the only independent protective factor, with an aOR of 0.22. Conclusion: PVD is the most important protective factor from uterine rupture in patients undergoing TOLAC. A trial of labor following one CD should therefore be encouraged in these patients.