π€° VBAC Success Factors Checker
Which factors favor a vaginal birth after cesarean?
Favorable VBAC factors
For informational purposes only, not medical advice.
Six factors from the Grobman VBAC prediction model shape the odds of vaginal birth after cesarean: younger age, lower BMI, prior vaginal delivery, prior VBAC, a non-recurring reason for the first cesarean, and spontaneous labor. Checking four of the six, as in 4 of 6, describes a moderate-to-higher likelihood profile. Overall, 60 to 80 percent of VBAC attempts succeed, according to ACOG.
An important honesty note: this page counts favorable factors for education. The clinical Grobman model computes a personalized probability with logistic regression; reproducing its exact coefficients here would pretend to a precision a web page cannot verify for you. The factor count organizes your thinking and your conversation with your OB, and the OB's counseling provides the number.
How to Use This Checker
Answer the six questions about your history and this pregnancy. The tool counts your favorable factors and places your profile in context.
Answer the history questions: age under 35, pre-pregnancy BMI under 30, any prior vaginal delivery, and any prior VBAC.
Answer the pregnancy questions: whether the prior cesarean was for a non-recurring reason like breech or fetal distress rather than labor arrest, and whether labor starts spontaneously.
Read your factor count and bring it to your prenatal visits. Ask your OB for their personalized estimate and their VBAC experience.
Why These Six Factors
Prior vaginal delivery is the heavyweight: a pelvis that has done it before usually does it again, and a prior VBAC is stronger still. Non-recurring indications matter because a cesarean for breech says nothing about labor capacity, while one for arrest of descent raises the question again. Higher BMI and induction both nudge success down modestly, and age effects are gradual rather than cliff-edged.
The Grobman model behind this list was validated on thousands of VBAC attempts and is the most studied prediction tool in obstetrics. Its message is encouraging: most candidates who attempt labor succeed, and the factors help identify who benefits most from trying.
Worked Example
A 32-year-old with pre-pregnancy BMI 27, one prior cesarean for breech, no prior vaginal delivery, planning induction at 39 weeks: yes to age, BMI, and non-recurring indication, no to the rest, totaling 4 of 6 favorable factors, a moderate profile.
Her counseling would note the encouraging pieces, young, healthy weight, breech indication, alongside the honest caveats: no proven pelvis and induction slightly lowers success. Many OBs would quote her a personal chance in the 60s, discuss uterine rupture risk around 0.5 to 1 percent, and support either choice. That conversation, not the factor count, makes the decision.
Reading Your Result
| Favorable factors | Profile |
|---|---|
| 5 to 6 | Higher likelihood. Most such attempts succeed; discuss proceeding with confidence. |
| 3 to 4 | Moderate likelihood. A genuine choice; the OB's personalized estimate matters most. |
| 0 to 2 | Lower likelihood. Still often reasonable to attempt with informed consent; discuss trade-offs carefully. |
My take: the factor count should expand your options, not restrict them. Even lower-count profiles succeed regularly, and the absolute risks of both paths, VBAC and repeat cesarean, are small. The right choice is the informed one you make with your doctor, not the one a checklist picks.
Limits
This checklist is deliberately not the Grobman probability: equal weighting of factors is a simplification, and real prediction needs the model's coefficients plus your clinician's judgment. It also cannot weigh scar type, inter-pregnancy interval, estimated fetal weight, or provider and hospital VBAC experience, all of which matter. Treat it as a discussion organizer.
Related Tools
Pregnancy planning tools pair naturally: the pregnancy due date calculator, the pregnancy weight gain calculator, and the ovulation calculator for timing.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the VBAC success rate?
About 60 to 80 percent of attempted VBACs result in vaginal birth, per ACOG. Success is highest with prior vaginal delivery and lowest with recurring indications like labor arrest, but most candidates who attempt labor succeed.
What is the Grobman model?
A validated prediction model for VBAC success using maternal age, BMI, prior vaginal delivery, prior VBAC, and whether the prior cesarean was for a recurring indication. It is the most studied VBAC prediction tool and informs counseling, though this page simplifies it to a factor checklist.
What is the strongest predictor of VBAC success?
Prior vaginal delivery, especially a prior VBAC. A proven pelvis outweighs every other factor in the models. Women with a prior VBAC have success rates well above the average.
What is the risk of uterine rupture with VBAC?
About 0.5 to 1 percent for one prior low-transverse cesarean. It is the key risk in VBAC counseling: uncommon but serious, which is why VBAC is recommended only where emergency cesarean is available.
Who should not attempt VBAC?
ACOG advises against it with prior classical or T-shaped uterine incisions, prior uterine rupture, or when the facility cannot perform emergency cesarean. Multiple prior cesareans need individualized counseling.
Does induction lower VBAC success?
Somewhat. Induced labor has modestly lower success rates than spontaneous labor in VBAC candidates, though many inductions still succeed. The indication for induction and cervical readiness both matter.
Does BMI affect VBAC success?
Higher pre-pregnancy BMI modestly reduces success rates in the models. It is one factor among several, not a disqualifier; many patients with higher BMI have successful VBACs.
What is a non-recurring indication?
A reason for the prior cesarean unlikely to repeat, such as breech presentation or fetal distress, as opposed to recurring ones like arrest of labor. Non-recurring indications predict better VBAC success.
Can I have a VBAC after two cesareans?
Sometimes, with careful counseling. Success rates are lower and rupture risk higher than after one, so ACOG calls it a reasonable option for selected candidates in equipped facilities, decided individually.
How should I use this checklist?
Count your favorable factors, then bring the result to your OB visits. Ask for their personalized estimate, their VBAC volume, and the hospital's emergency readiness. The checklist starts the conversation; your doctor finishes it.