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Vaginal birth after cesarean (VBAC) probability calculator
Predicted probability of successful VBAC for counseling on trial of labor.
Vaginal birth after cesarean (VBAC) probability calculator
Maternal age
years
Pre-pregnancy weight
Height
Arrest of dilation or descent was the indication for the prior cesarean delivery
Vaginal delivery before the prior cesarean delivery (but no VBAC since)
Prior successful VBAC (vaginal delivery after a prior cesarean delivery)
Treated chronic hypertension
Complete the fields above to see the result.
When to use
- Antenatal counseling of a woman with one prior cesarean delivery who is considering a trial of labor after cesarean (TOLAC).
Formula
w = −5.952 − 0.023×age(yr) − 0.024×weight(kg) + 0.056×height(cm) − 0.597×arrest-of-labor indication(0/1) + 0.868×prior vaginal delivery only(0/1) + 1.869×prior VBAC(0/1) − 0.966×treated chronic hypertension(0/1); predicted probability (%) = exp(w) / (1 + exp(w)) × 100.
Pearls and pitfalls
- This 2021 model removed maternal race and ethnicity from the original 2007 Grobman nomogram after they were shown to systematically lower predicted probabilities for Black and Hispanic patients.
- Applies to term, singleton, vertex pregnancies with exactly one prior low-transverse cesarean delivery; not validated for prior classical or unknown uterine incisions.
References
- Grobman WA, Sandoval G, Rice MM, et al. Prediction of vaginal birth after cesarean delivery in term gestations: a calculator without race and ethnicity. Am J Obstet Gynecol. 2021;225(6):664.e1-664.e7.
- Grobman WA, Lai Y, Landon MB, et al. Development of a nomogram for prediction of vaginal birth after cesarean delivery. Obstet Gynecol. 2007;109(4):806-812.