VBAC Calculator

Author: Henrick Yau

- 5 October 2026

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This calculator helps estimate your chances of successful vaginal birth after a previous cesarean section (VBAC). Enter your details below to get a personalized assessment.

Personal Information

Maternal Age:

BMI (Body Mass Index):

Enter your pre-pregnancy or current BMI

Obstetric History

Prior Vaginal Birth:

Prior Successful VBAC:

Number of Previous Cesareans:

Reason for Previous Cesarean:

Current Pregnancy

Gestational Age at Delivery:

Estimated Fetal Weight:

Induction Planned:

Bishop Score (if known):

Leave at 5 if unknown

Additional Risk Factors

Gestational Diabetes

Hypertensive Disorder

Suspected Fetal Macrosomia

Short Interpregnancy Interval (<18 months)

Understanding VBAC Success Factors

The likelihood of successful vaginal birth after cesarean depends on many factors. This calculator uses evidence-based research to estimate success rates, but individual outcomes may vary.

Key Predictive Factors

Prior Vaginal Birth: A previous successful vaginal delivery significantly increases VBAC success rates
Reason for Prior Cesarean: Non-recurring reasons (like breech position) generally have better VBAC outcomes
Maternal Age: Younger maternal age is associated with higher success rates
BMI: Lower BMI is linked to higher VBAC success rates
Induction: Spontaneous labor typically has higher success rates than induced labor

VBAC Benefits

Shorter recovery time
Lower risk of surgical complications
Reduced risk of respiratory problems for baby
Earlier mother-baby contact and breastfeeding
Higher likelihood of successful vaginal births in future pregnancies

VBAC Risks

Uterine Rupture: Rare but serious complication (0.5-1% with one prior cesarean)
Failed VBAC: May lead to emergency cesarean, which carries higher risks than planned cesarean
Blood Transfusion: Slightly increased risk compared to planned repeat cesarean

Disclaimer: This calculator provides estimates based on statistical models and research data. It is for informational purposes only and should not replace professional medical advice. Always consult with your healthcare provider to make decisions about your delivery options. Individual outcomes may vary based on numerous factors not accounted for in this tool.

VBAC Success Probability Formula (Simplified):


    Estimated Success Rate = Base Rate (72%) + Sum of Positive and Negative Adjustments

Each adjustment is based on individual factors like maternal age, BMI, previous birth history, and current pregnancy conditions.

What the VBAC Calculator estimates

The VBAC (Vaginal Birth After Caesarean) Calculator is a useful tool for pregnant women who have had one or more caesarean deliveries. It estimates the likelihood of achieving a successful vaginal birth in a future pregnancy. The calculator uses evidence-based data from medical research and applies a formula that takes into account age, BMI, delivery history, and current pregnancy details.

How a personalised success estimate supports your planning

Planning for childbirth after a caesarean can feel uncertain. The VBAC Calculator helps by offering a personalised estimate of success, giving expectant mothers and their healthcare providers an extra layer of insight. Here’s how it can support your decision-making:

Provides a clear percentage estimate of successful vaginal delivery
Highlights both positive and negative influencing factors
Shows the risk of uterine rupture based on your profile
Offers visual data to better understand your chances
Gives tailored tips and suggestions for birth planning

Entering your details to calculate your VBAC chance

Using the calculator is straightforward and takes only a few minutes. Here's how:

Step 1: Enter your age and pre-pregnancy BMI
Step 2: Fill in your obstetric history—past vaginal births, VBAC attempts, and reasons for previous caesareans
Step 3: Provide current pregnancy information—gestational age, fetal weight, induction plans, and Bishop score
Step 4: Select any additional risk factors like gestational diabetes or hypertension
Step 5: Click “Calculate VBAC Success Rate” to view your results

You’ll see your personalised success rate, risk level, and recommendations for a safer and more informed birth experience.

Who Should Use This Tool?

This calculator is helpful for individuals who:

Are currently pregnant and had a caesarean before
Are exploring delivery options and want to understand their VBAC chances
Want to discuss data-backed options with their care provider

Questions about VBAC success prediction

Is this calculator a substitute for medical advice?

No. This tool is for informational purposes only. Always discuss your results and delivery options with your doctor or midwife.

How accurate is the VBAC success rate?

The calculator uses a large body of clinical research to provide estimates, but personal medical conditions may affect your actual outcome.

What does a “good” success rate mean?

A score above 70% generally suggests a higher likelihood of success, but outcomes depend on many variables. Your healthcare provider can help interpret your score in context.

How does this compare to other tools like a pregnancy calculator or ovulation tracker?

The VBAC Calculator focuses specifically on delivery outcomes after a caesarean. Other tools—like a pregnancy week calculator, fertility calendar, or pregnancy weight guide—track timelines, weight, and fertile windows. Each plays a different role in pregnancy and fertility planning.

Can I use this tool with others like a due date estimator or conception calculator?

Yes. Many women use this alongside tools like a baby due date tool, conception date estimator, or fertility tracking resource to gain a complete picture of their reproductive health journey.

Why VBAC Planning Matters

Choosing between VBAC and a repeat caesarean can have long-term effects on your health and future pregnancies. This calculator empowers you with data so you can talk confidently with your care team. It works well with tools like a pregnancy due date calculator, track pregnancy timeline apps, and ovulation tracking guides.

Using the VBAC Calculator to inform your birth plan

The VBAC Calculator is a valuable step in understanding your delivery options. With clear insights into success probability and potential risks, you can better prepare for a safer and more informed birth. Always combine this information with professional medical guidance to make the best decision for you and your baby.