VBAC/TOLAC Success Probability Calculator (Grobman Model)

Estimate probability of vaginal birth after cesarean (VBAC) using the Grobman nomogram. Inputs include age, BMI, prior vaginal delivery, prior VBAC, prior cesarean indication, cervical exam, and ethnicity.

Weight
Height
Clinical Guidance

BMI is a screening measure of body size, not a direct measure of body fat. The standard WHO categories are underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

BMI can overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Interpret it alongside waist circumference and clinical context rather than as a standalone diagnosis.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.
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How It Works

Estimate probability of vaginal birth after cesarean (VBAC) using the Grobman nomogram. Inputs include age, BMI, prior vaginal delivery, prior VBAC, prior cesarean indication, cervical exam, and ethnicity

Each component has a specific meaning:

  • Grobman nomogram — The grobman nomogram recorded for the scenario being assessed.

Note: Interpret the vbac/tolac success result against the thresholds and context described above.

How to Use

Enter the Grobman nomogram for the scenario you are assessing. Estimate probability of vaginal birth after cesarean (VBAC) using the Grobman nomogram. Inputs include age, BMI, prior vaginal delivery, prior VBAC, prior cesarean indication, cervical exam, and ethnicity. Use the vbac/tolac success result to inform your calculation.

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Frequently Asked Questions