Uterine Rupture: Risk Factors

Uterine rupture is a catastrophic obstetric emergency defined as a full-thickness disruption of the uterine wall, classified as complete (all layers including serosa disrupted, with fetal parts extruding into the peritoneal cavity) or incomplete (uterine muscle disrupted but visceral peritoneum/serosa remains intact, also called uterine dehiscence). Complete rupture carries significantly higher maternal and fetal mortality. The most important risk factor is a prior uterine scar, particularly from a previous classical (vertical) cesarean incision, which has a 4-9% rupture risk during subsequent labor compared to 0.2-0.7% for a prior low-transverse incision. Trial of labor after cesarean (TOLAC) is considered acceptable for patients with one prior low-transverse cesarean scar, but is contraindicated with prior classical or T-incision scars, prior uterine rupture, or more than two prior cesarean deliveries. Rupture occurs when intrauterine pressure during contractions exceeds the tensile strength of the scarred myometrium. The low-transverse scar sits in the passive lower segment with less contractile stress, while the classical scar traverses the actively contracting upper segment, explaining the difference in rupture rates. Oxytocin augmentation and prostaglandin cervical ripening agents (misoprostol, dinoprostone) significantly...