ToolsCalculators
VBAC Risk Score for Successful Vaginal Delivery (Flamm)
Predicts likelihood of successful vaginal birth after cesarean.
VBAC Risk Score for Successful Vaginal Delivery (Flamm)
Age < 40 years
Vaginal birth history
Reason for prior cesarean other than failure to progress
Cervical effacement at admission
Cervical dilation >= 4 cm at admission
Result0 points
Estimated probability of successful VBAC about 49%.
- Predicted VBAC success
- 49%
When to use
- Counselling patients considering a trial of labour after cesarean about likelihood of success.
Formula
Points: age <40 = 2; vaginal birth history (both before and after = 4, after only = 2, before only = 1); prior cesarean not for failure to progress = 1; effacement (>75% = 2, 25-75% = 1); dilation >=4 cm = 1. Range 0-10; higher scores predict higher VBAC success (about 49% at 0-2 up to ~95% at 8-10).
Pearls and pitfalls
- Estimates likelihood of success, not the risk of uterine rupture, which must be weighed separately.