Unintentional Extensions of the Cesarean Hysterotomy Incision: A Review and Proposed Classification System

Unintentional hysterotomy extensions are common but poorly defined complications of cesarean delivery. This narrative review synthesizes observational and interventional studies evaluating the definition, incidence, risk factors, and sequelae of hysterotomy extensions, and summarizes available evidence on preventative strategies. Cesarean delivery in the second stage of labor consistently emerges as the strongest independent predictor of hysterotomy extensions. Hysterotomy extensions are reliably associated with greater blood loss, higher transfusion rates, longer operative times, and increased risk of intraoperative injury. Evidence regarding subsequent uterine rupture is conflicting and limited. In contrast, several cohorts suggest that cervical or lower-segment trauma may increase the risk of spontaneous preterm birth in later pregnancies. Randomized and comparative studies suggest several delivery methods that may reduce hysterotomy extension. Overall, unintentional hysterotomy extension appears to be a frequent, morbid, and underrecognized complication of cesarean birth for which standardized terminology, a pragmatic grading system, and higher-quality prospective data are needed.