Calculating Your VBAC Odds
If you have had a c-section in the past, you may be wondering if you are a good candidate for a Vaginal Birth After Cesarean (VBAC) for your current pregnancy. While the phrase "once a c-section, always a c-section" was medical gospel decades ago, it is completely outdated today.
Our VBAC Calculator uses the updated, race-neutral MFMU (Maternal-Fetal Medicine Units) clinical model. This is the exact same mathematical formula many obstetricians use to help counsel patients on their delivery options.
Factors That Affect VBAC Success
The mathematical model uses several key pieces of your obstetric and physical history to calculate your odds of success:
- Prior Vaginal Delivery: This is the strongest predictor of a successful VBAC. If your body has successfully delivered a baby vaginally in the past (either before or after your c-section), your odds of success skyrocket.
- Reason for Prior C-Section: Why did you have your last c-section? If it was for a one-time issue like a breech baby or fetal distress, your odds of a successful VBAC are very high. If it was for "Failure to Progress" (you were stuck at 6cm dilated for hours), your odds are slightly lower, but a VBAC is absolutely still possible.
- Maternal Age & BMI: Younger age and lower Body Mass Index (BMI) at the time of delivery generally correlate with higher VBAC success rates.
What is a "Good" Score?
According to ACOG, a calculated probability greater than 60-70% means you have roughly the same chance of a successful vaginal delivery as a first-time mother. However, even if your calculated probability is 40%, you still have a 4 in 10 chance of success. Many women with "low" scores go on to have incredibly smooth, successful VBACs.