Single Most Important Predictor of Successful Vaginal Birth After Cesarean Section

Having had a previous vaginal birth is the single most important predictor of successful vaginal birth after cesarean section (VBAC). 1, 2

Key Predictors of VBAC Success

Previous vaginal delivery, particularly a previous successful VBAC, is strongly associated with higher rates of successful vaginal delivery in subsequent pregnancies 1, 2, 3
About 74% of U.S. women who attempt labor after cesarean (LAC) have a successful vaginal birth 1
Women with a history of previous vaginal delivery have significantly higher odds of successful VBAC (odds ratio 3.90,95% CI 2.1-7.4) 3
Non-recurrent indications for the previous cesarean section (such as fetal distress, breech presentation) significantly increase the likelihood of successful VBAC compared to recurrent indications like cephalopelvic disproportion 3

Higher Bishop scores and more progression in labor at admission increase the likelihood of successful VBAC 1, 4
Cervical dilation of more than 3cm at admission is associated with successful VBAC 4
Rupture of membranes at admission is a positive predictor for successful VBAC 4
The likelihood of successful VBAC decreases when:
- Labor is induced using oxytocin 1
- Estimated fetal weight is ≥4,000g (8 lb, 13 oz) 1, 5
- Presence of meconium or malposition is noted 4

Labor induction carries varying risks of uterine rupture depending on the method used 1:
- Oxytocin: 1.1% (95% CI, 0.9% to 1.5%)
- Prostaglandin E2: 2% (95% CI, 1.1% to 3.5%)
- Misoprostol: 13% (based on one fair-quality cohort study)
Misoprostol should not be used for cervical preparation or induction of labor in women with a previous cesarean delivery 1
While short-term maternal outcomes are as good or better with VBAC compared to repeat cesarean delivery, perinatal mortality is slightly higher 1

For most women who have had one or two cesarean deliveries, attempting VBAC is practical and safe 1
Physicians should discuss the possibility of VBAC early in prenatal care, considering each patient's risk factors 1
While predictive scoring models have been developed, they have limited value in determining which women have a greater risk of cesarean delivery 1, 6
When counseling patients, emphasize that those with a previous vaginal delivery have approximately 85% chance of successful VBAC 5
Physicians should reevaluate the labor plan when patients present in labor, considering factors that may affect the chance of delivering vaginally 1

Failing to recognize the significance of previous vaginal delivery as the strongest predictor of VBAC success 1, 2, 3
Using misoprostol for cervical ripening or induction in women with previous cesarean delivery 1
Not considering the indication for previous cesarean section when counseling about VBAC success 3
Overlooking the importance of cervical status at admission (dilation, effacement, station) as predictors of success 1, 4
Underestimating the impact of fetal weight on VBAC success rates 1, 5