Overview
Clinical Meaning
Vaginal birth after cesarean (VBAC) refers to a successful vaginal delivery in a patient with a prior cesarean section.
Vaginal birth after cesarean (VBAC) refers to a successful vaginal delivery in a patient with a prior cesarean section. Trial of labor after cesarean (TOLAC) is the planned attempt at vaginal delivery. The primary concern during TOLAC is uterine rupture, which occurs when the prior cesarean scar (typically a low transverse hysterotomy) separates during labor. Uterine rupture occurs in approximately 0.5-0.7% of TOLAC attempts with a prior low transverse incision but rises to 4-9% with a prior classical (vertical) incision, making classical incisions an absolute contraindication. During rupture, the myometrium separates at the scar, and the fetus, placenta, or both may be extruded partially or completely into the peritoneal cavity, causing catastrophic maternal hemorrhage, fetal hypoxia, and potential maternal or fetal death. The clinician evaluates TOLAC candidacy using validated prediction models (MFMU VBAC Success Calculator) incorporating factors such as: prior vaginal delivery (strongest positive predictor, success >85%), indication for prior cesarean (failure to progress vs. non-recurrent indication), cervical dilation at admission, BMI, maternal age, interpregnancy interval (>18 months preferred), and gestational age. Absolute contraindications include prior classical or T-incision, prior...
