Estimate VBAC success with a legacy Grobman-style counseling model, framed as discussion support rather than a stand-alone eligibility rule.
This page estimates VBAC success with a Grobman-style counseling model for trial of labor after cesarean (TOLAC). It uses age, BMI, delivery history, prior cesarean indication, and cervical findings to generate a rough success probability that can help structure counseling.
The key limitation is that the legacy published model includes race-adjusted coefficients and was designed as a counseling aid, not as a gatekeeping rule. Because of that, the most honest way to read this page is as a legacy decision-support model rather than as a definitive answer about whether a patient should or should not attempt TOLAC.
Use the output only in the context of clinician counseling, obstetric history, uterine-scar details, facility capability, and patient preferences.
A VBAC counseling model can be useful when the discussion has become too abstract and the team needs a rough estimate of how favorable the labor history and current presentation look.
Its value is in structuring conversation. It should not override clinical eligibility, patient goals, or a modern individualized discussion of uterine rupture risk, emergency cesarean access, and other pregnancy-specific factors.
MFMU VBAC Prediction Model (simplified Grobman): Logit = 3.766 - (0.039 × age) - (0.067 × BMI) - 0.671 (if African American) - 0.468 (if Hispanic) + 0.888 (if prior vaginal delivery) + 1.003 (if prior VBAC) + 0.446 (if non-recurring indication) + 0.105 × cervical dilation (cm) + 0.017 × effacement (%) Probability = 1 / (1 + e^(-logit))
Result: Predicted VBAC Success: 78.3%
This profile has several factors that improve modeled success, including prior vaginal delivery, a non-recurring prior cesarean indication, and a favorable cervix. The result should be used to support counseling, not to substitute for the full TOLAC eligibility discussion or to impose a numeric cutoff.
This page is useful when the counseling discussion needs a rough legacy-model estimate of VBAC success instead of an unstructured impression.
It does not determine eligibility for TOLAC, and it should not be used to deny TOLAC because of a single number. The race-adjusted coefficients in the historical model are one reason to read it cautiously.
Use it as one part of a shared decision-making conversation that also covers scar type, prior birth history, facility capability, induction plans, and patient values.
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This page reproduces a legacy Grobman-style VBAC counseling model that estimates the probability of successful vaginal birth after cesarean from age, BMI, delivery history, prior cesarean indication, and cervical findings. It is intentionally framed as a counseling aid rather than a stand-alone eligibility rule.
Because the historical model included race-adjusted coefficients, the output should be read cautiously and should not be used to offer or deny TOLAC by itself. Modern counseling still depends on the broader obstetric picture, uterine-scar history, facility capability, and patient preferences.
There is no universal go/no-go cutoff. The number is one counseling input, and the decision still depends on clinical eligibility, uterine-scar history, emergency cesarean capability, and patient preferences.
With one prior low-transverse cesarean, uterine rupture risk during TOLAC is roughly 0.5% to 0.7%. Risk is higher with classical scars, multiple prior cesareans, short inter-delivery intervals, and some induction methods.
Yes. Induction can lower VBAC success compared with spontaneous labor, and induction planning should follow current obstetric guidance for TOLAC candidates.
The legacy published model included race-adjusted coefficients, which is one reason the calculator should be treated as a historical counseling model rather than a stand-alone decision rule. Many clinicians now prefer counseling approaches that do not let race-based coefficients decide access to TOLAC.
This model was primarily developed for patients with one prior cesarean. TOLAC after two prior cesareans needs separate counseling and institution-specific capability review.
Yes, but the estimate is rougher before admission because cervical findings are not yet known. Prenatal counseling should still focus on the full obstetric context rather than the model alone.