Estimate the chance of a successful vaginal birth after caesarean with the Grobman 2021 refit model, which uses no race or ethnicity terms.
Result
How to use this tool
Enter age, pre-pregnancy weight and height.
Say whether the prior caesarean was for arrest of dilation or descent.
Say whether there was a vaginal delivery before it, or a previous VBAC.
Flag medication-treated chronic hypertension, then read the chance as counselling information.
Formula & worked example
Age 30, 70 kg, 165 cm, no arrest indication, a vaginal delivery before the prior caesarean, no prior VBAC and no treated hypertension gives w = 1.79 and a chance of about 85.7%.
Limitations — read this before you rely on it
Counselling aid only, from a US cohort; not validated for every population and not a substitute for obstetric advice. It estimates success only, not rupture or other risks. This tool is for education only and is not medical advice. Talk to a clinician about any result that worries you, and never change treatment because of a calculator result.
Frequently asked questions
A vaginal birth after a previous caesarean, usually attempted as a trial of labour (TOLAC) in a suitable hospital.
The 2021 refit removed those terms; it kept the same discrimination (AUC about 0.75) without them.
No. It is a population estimate from a US academic-centre cohort and individual outcomes vary.
This model estimates success only, not rupture risk, which must be discussed separately with an obstetrician.
It was developed for people with one prior low transverse caesarean at term with a singleton vertex pregnancy.