VBAC Calculator – Vaginal Birth After Cesarean

Vaginal birth after cesarean section (VBAC) refers to a planned attempt to deliver vaginally when a woman has had one or more previous cesarean deliveries. VBAC is an important option in modern obstetric care because it can offer several advantages over repeat cesarean section, including shorter maternal recovery time, fewer surgical complications, lower risk of uterine adhesions, and in some cases better outcomes for future pregnancies. However, VBAC also carries a small but real risk of uterine rupture, which occurs in approximately 0.5–1% of attempted labors after cesarean. Successful VBAC rates in published studies range broadly from 60% to 80%, with individual outcomes strongly influenced by patient-specific clinical factors. The most powerful predictor is whether the woman has previously delivered vaginally: women with at least one prior vaginal delivery — either before or after the cesarean — have substantially higher success rates than those with no prior vaginal births. The reason for the original cesarean also matters: non-recurring indications such as breech presentation or placenta previa generally predict better outcomes than recurring ones such as failure to progress or cephalopelvic disproportion. Other factors that affect VBAC success include maternal age (younger women generally have higher success rates), pre-pregnancy BMI (obesity reduces VBAC success), gestational age at delivery, the presence of gestational diabetes or hypertension, and the method of labor induction if labor does not start spontaneously. Prostaglandin cervical ripening agents are associated with a higher risk of uterine rupture and are generally avoided in VBAC candidates; spontaneous onset of labor carries the lowest risk. This calculator uses a scoring model derived from published VBAC predictor research to generate an estimated probability. It weighs each clinical factor based on its known association with VBAC success in large observational studies. The model is educational and simplified; it does not replace the validated nomograms developed by Grobman and colleagues using the MFMU Network dataset, which remain the gold standard for VBAC counseling in clinical practice. Candidates for VBAC should be counseled in detail by their obstetric team. Absolute contraindications include prior classical (vertical) uterine incision, prior uterine rupture, and certain uterine surgeries. Attempted VBAC should occur in a facility capable of emergency cesarean delivery. Continuous fetal heart rate monitoring during labor is standard of care. This tool is for informational and educational use only. It should not be used as a substitute for individualized clinical assessment by a qualified healthcare provider.