Unintended lower-segment hysterotomy extension at cesarean delivery and the risk for uterine rupture during a subsequent trial of labor

Objective: To evaluate the association between unintended uterine extension in cesarean delivery and uterine scar disruption (rupture or dehiscence) at the subsequent trial of labor after cesarean delivery (TOLAC). Methods: This is a multicenter retrospective cohort study (2005–2021). Parturients with a singleton pregnancy who had unintended lower-segment uterine extension during the primary cesarean delivery (excluding T and J vertical extensions) were compared with patients who did not have an unintended uterine extension. We assessed the subsequent uterine scar disruption rate following the subsequent TOLAC and the rate of adverse maternal outcome. Results: During the study period, 7199 patients underwent a trial of labor and were eligible for the study, of whom 1245 (17.3%) had a previous unintended uterine extension and 5954 (82.7%) did not. In univariate analysis, previous unintended uterine extension during the primary cesarean delivery was not significantly associated with uterine scar rupture in the following subsequent TOLAC. Nevertheless, it was associated with uterine scar dehiscence, higher rates of TOLAC failure, and a composite adverse maternal outcome. In multivariate analyses, only the association between previous unintended uterine extension and higher rates of TOLAC failure was confirmed. Conclusion: A history of unintended lower-segment uterine extension is not associated with an increased risk for uterine scar disruption following subsequent TOLAC.