VBAC Risk Score Calculator — Flamm-Geiger Admission Score
The Flamm-Geiger Admission Score (1997) assigns points to five clinical criteria at the time of hospital admission to estimate the likelihood of a successful vaginal birth after cesarean (VBAC). Score 0–10, with higher values indicating greater VBAC likelihood.
Maternal age
Prior vaginal delivery history
Indication for prior cesarean
Cervical effacement on admission
Cervical dilation on admission
Flamm-Geiger score: 0 (lowest likelihood) to 10 (highest likelihood) of VBAC success
- 1
Age points (< 40 yr = 2, ≥ 40 yr = 0)
2 - 2
Prior vaginal delivery points
1Before prior CS = 1 pt; prior VBAC = 4 pts; none = 0 pts. - 3
Cervical criteria (indication + effacement + dilation)
1 + 1 + 0 = 2 - 4
Total VBAC admission score
2 + 1 + 2 = 5
How does this calculator work?
Flamm-Geiger VBAC Admission Score: Age <40 (2 pts) + Prior VD before CS (1) or prior VBAC (4) + non-recurring indication (1) + effacement ≥75% (1) + dilation ≥4 cm (1) = max 10. Score ≤2: ~49% success; 3–4: ~60–68%; 5–6: ~77–89%; 7–10: ~85–89%. Source: Flamm & Geiger, Obstet Gynecol 1997.
Formula
How this is calculated
The Flamm-Geiger VBAC Admission Score was developed by Flamm and Geiger (Obstetrics and Gynecology, 1997) from a multi-centre cohort of women undergoing trial of labour after cesarean (TOLAC). Five criteria available at admission are each scored: maternal age under 40 (2 points, as older age is associated with lower VBAC rates); prior vaginal delivery history — a prior vaginal delivery before the index cesarean (1 point) or a prior successful VBAC (4 points, the strongest predictor); a non-recurring indication for the previous cesarean — breech presentation, placenta previa, or similar conditions that will not recur (1 point), as opposed to recurring causes like cephalopelvic disproportion or failure to progress; cervical effacement of ≥75% on admission (1 point); and cervical dilation of ≥4 cm on admission (1 point).
The maximum score is 10. In the original validation cohort, scores ≤2 were associated with approximately 49% VBAC success; scores of 3–4 with approximately 60–68%; scores of 5–6 with approximately 77–89%; and scores of 7–10 with approximately 85–89%. The strong weighting on prior vaginal delivery (especially prior VBAC) reflects its dominant predictive value.
Limitations: the score was derived in 1990s US hospital settings and has been validated in several but not all populations. It does not account for the specific reason for failure in prior labours, maternal obesity (BMI), or indication for the current induction. The MFMU (Maternal-Fetal Medicine Units Network) calculator published by Grobman et al. (2007) offers a more detailed multivariable logistic model including ethnicity and BMI but requires a computer-based nomogram. This score is one clinical input; delivery decisions require full obstetric clinical assessment.
Frequently asked questions
In the Flamm-Geiger validation study, scores of 5 or above were associated with VBAC success rates of approximately 77–89%. Scores of 8–10 reflect the combination of favourable cervix, prior VBAC history, and non-recurring indication — the highest-probability profile. Scores ≤2 were associated with approximately 49% success, reflecting an unfavourable clinical picture where some units would counsel towards elective repeat cesarean (ERCS).
TOLAC (trial of labour after cesarean) refers to the attempt at vaginal delivery after a prior cesarean, whereas VBAC (vaginal birth after cesarean) is the successful outcome — the actual vaginal delivery. When a TOLAC is unsuccessful, the birth ends in a repeat cesarean. Scoring systems like Flamm-Geiger predict the probability that a TOLAC will result in a VBAC rather than an unplanned repeat cesarean.
A prior VBAC proves that the woman has already delivered vaginally after a uterine scar, directly demonstrating that her pelvis and uterus can accommodate vaginal birth in that clinical context. This is a far stronger predictor of success than having had a vaginal delivery before the cesarean (which occurred under different circumstances). Accordingly, the Flamm-Geiger model assigns 4 points to prior VBAC versus just 1 point for prior vaginal delivery before the index cesarean.
Also known as
TG we-Calculate Editorial Team. (2026). VBAC Risk Score Calculator — Flamm-Geiger Admission Score [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/vbac-risk-score-calculator
TG we-Calculate Editorial Team. "VBAC Risk Score Calculator — Flamm-Geiger Admission Score." TG we-Calculate. 2026. https://we-calculate.com/calculator/vbac-risk-score-calculator.
TG we-Calculate Editorial Team, "VBAC Risk Score Calculator — Flamm-Geiger Admission Score," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/vbac-risk-score-calculator
@misc{wecalculate_vbac_risk_score_calculator, title = {VBAC Risk Score Calculator — Flamm-Geiger Admission Score}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/vbac-risk-score-calculator}}, year = {2026}, note = {TG we-Calculate} }
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