VBAC Success Calculator (Flamm Score)
Calculate the probability of a successful Vaginal Birth After Cesarean (VBAC) at admission for labor.
The Flamm Score: Predicting VBAC Success
The Flamm Score is a validated and easy-to-use clinical tool that estimates the chances of a successful Trial of Labor After Cesarean (TOLAC) resulting in a Vaginal Birth After Cesarean (VBAC).
Why use this score?
This 10-point score uses data readily available at admission to the labor ward to counsel the patient:
- Decision making: Encourages trial of labor in patients with a high score (> 4).
- Risk management: Identifies patients with a low probability of success (score ≤ 2) to consider an early repeat cesarean, minimizing maternal and fetal morbidity risks associated with prolonged labor.
Risk Factors and Contraindications
VBAC is generally contraindicated in cases of a classical (vertical) uterine incision, a history of uterine rupture, or major obstetric contraindications (e.g., placenta previa). Continuous fetal monitoring is imperative during a trial of labor (TOLAC).
Probability of Success by Score
| Flamm Score | Success Probability |
|---|---|
| 0 - 2 pts | 49 % |
| 3 pts | 60 % |
| 4 pts | 67 % |
| 5 pts | 77 % |
| 6 pts | 89 % |
| 7 pts | 93 % |
| 8 - 10 pts | 95 % |
References:
1. Flamm BL, Geiger AM. Vaginal birth after cesarean delivery: an admission scoring system. Obstet Gynecol. 1997;90(6):907-10.
[NIH - PubMed]
2. ACOG Practice Bulletin No. 205. Vaginal Birth After Cesarean Delivery. Obstet Gynecol. 2019;133(2):e110-e127.
[ACOG Official]
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