VBAC Counseling Support Tool

VBAC Probability Calculator

Estimate the likelihood of a successful vaginal birth after cesarean (VBAC) using research-informed clinical factors such as age, BMI, prior births, indication for cesarean, Bishop score, and labor characteristics.

The calculation logic is loosely inspired by validated VBAC prediction models and published cohort data, but it does not reproduce any single proprietary or guideline calculator. It is designed for education and counseling support only.

Enter clinical details

More complete and realistic data will give a more tailored estimate. Use the best information you have available, or typical/rounded values if you are unsure.

Maternal age (years)

VBAC success is usually higher at younger ages and gradually decreases after the mid-30s.

BMI before pregnancy

Higher BMI can lower the chance of VBAC and increase surgical risk, but many people still have successful VBACs.

Number of prior vaginal births

Any prior vaginal birth, especially after the cesarean, is a strong positive factor.

History of previous VBAC?

A previous successful VBAC usually predicts a high chance of success again.

Indication for prior C-section

Non-recurrent indications are generally more favorable than true “failure to progress” reasons.

Onset of labor

Spontaneous labor tends to have higher success and slightly lower rupture risk than induction.

Bishop score at admission

Higher scores (more favorable cervix) are linked with better chances of vaginal birth, including VBAC.

Estimated fetal weight (grams) (optional)

Larger babies may reduce the chance of VBAC somewhat, especially if there was previous concern about pelvic fit.

This tool assumes a singleton pregnancy, one prior low-transverse cesarean, and no absolute contraindications to labor (such as placenta previa or prior uterine rupture). Those situations require specialist review.

Your VBAC probability estimate

This is an approximate percentage based on a research-inspired scoring model. It is meant to support conversations, not to guarantee any outcome or to replace your clinician’s judgment.

Estimated chance of successful VBAC

–%

Success category: –

Success category

Lower chance Higher chance

You

Your VBAC estimate

–%

An approximate probability based on the answers you entered.

Typical VBAC success

≈ 60–80%

Many large studies report overall success rates in this general range for well-selected candidates.

Uterine rupture risk

≈ 0.3–0.7%

For one prior low-transverse cesarean with trial of labor. Your individual risk may differ.

Positive factors in your profile

These features are generally associated with higher VBAC success in published research and validated prediction models.

Factors that may reduce your VBAC likelihood

These points do not mean VBAC is unsafe or impossible, but they may lower the chance of success or warrant closer monitoring.

Counseling notes and limitations

VBAC can reduce the lifetime number of cesareans and is often associated with fewer complications than multiple repeat cesareans, especially for future pregnancies.
The highest risk situation is usually a failed trial of labor that ends in an urgent cesarean. Planning, monitoring and clear thresholds for intervention are crucial.
This calculator does not include all important factors, such as the number of prior cesareans, inter-pregnancy interval, type of uterine closure, medical conditions, or local hospital policies.
Use this estimate as a starting point for shared decision making. It should never be the only reason to offer or deny a trial of labor after cesarean (TOLAC).

Important safety notice This calculator is for information and education only. It does not provide medical advice, diagnosis, or treatment and should not replace individualized assessment by an obstetric professional. The numbers are approximate and may not match official calculators or your local hospital’s data.

How to use this result Discuss this estimate with your obstetrician, midwife, or maternity team. Ask them to review your operative notes, clarify why your prior cesarean was done, interpret your Bishop score, and explain how your hospital manages VBAC, induction, and emergency cesarean.