VBAC Success Score Calculator

VBAC Success Score Calculator for Obstetrics & Gynecology. Higher historical scores describe more favorable admission characteristics within the model, but this implementation deliberately avoids low-probability and high-probability labels. ACOG advises against using a calculator score to block access to a trial of labor after cesarean; its advisory was reaffirmed in September 2025. The score does not estimate uterine rupture, compare all benefits and harms of repeat cesarean, or establish eligibility. Preferences and clinical assessment remain central.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

This implements the historical Flamm-Geiger 1997 admission score, not the contemporary NICHD prediction equation. Five contributions are added: the age contribution changes at 40 years; the four vaginal-birth-history categories contribute 0, 1, 2 or 4; the first-cesarean indication contributes 0 or 1; effacement contributes 0 below 25%, 1 from 25% through 75%, and 2 above 75%; dilation contributes 1 at 4 cm or greater. The total is 0-10. No cohort percentage is returned as a personal probability, and no race or ethnicity input is used.

When to use this calculator

Use this historical score for a documented admission assessment or educational comparison of scoring methods. It requires information available during the current labor admission, so it is not an early-pregnancy counseling calculator with guessed cervical findings. Flamm and Geiger studied 5022 trial-of-labor patients split into derivation and testing groups. That study design does not validate this website or establish applicability to every contemporary setting.

Inputs used

  • Completed maternal age in years, with no default assumption about being under 40.
  • Vaginal birth history before, after, both sides of, or never relative to the first cesarean.
  • Documented indication for the first cesarean, distinguishing failure to progress from another reason.
  • Cervical effacement percentage and dilation in cm from the current labor admission examination.
  • Explicit confirmation that admission measurements are available; unknown history is not a negative finding.

Clinical interpretation

Higher historical scores describe more favorable admission characteristics within the model, but this implementation deliberately avoids low-probability and high-probability labels. ACOG advises against using a calculator score to block access to a trial of labor after cesarean; its advisory was reaffirmed in September 2025. The score does not estimate uterine rupture, compare all benefits and harms of repeat cesarean, or establish eligibility. Preferences and clinical assessment remain central.

Worked example

At age 32, with a vaginal birth before but not after the first cesarean, a prior indication other than failure to progress, admission effacement 75% and dilation 4 cm, the contributions are 2 + 1 + 1 + 1 + 1 = 6. Effacement exactly 75% receives one point; 75.1% receives two. Holding all other example inputs constant, age 40 reduces the total to 4. Those boundary changes describe the historical rule, not abrupt biological changes in the chance of birth.

Limitations and safety notes

The original model and later studies have different populations and care patterns, so percentages are not automatically transportable. A small external prospective study cannot provide a universal calibration. Missing indication, unknown vaginal-birth history or unavailable cervical findings must not be scored as absence. Numeric entry bounds are technical scope limits, not study-derived eligibility criteria. Prior incision type, contraindications, fetal presentation, resources for emergency care and other important clinical details are not modeled. No patient-level validation of this implementation is claimed.

Frequently asked questions

Is a score of 6 the same as a 60% chance of VBAC?

No. Points are not percentages. Neither multiplying the score by ten nor assigning a historical cohort percentage creates a validated personal estimate. This calculator reports the arithmetic and its context only.

References

  • https://pubmed.ncbi.nlm.nih.gov/9397100/
  • https://www.jogi.co.in/storage/files/predicting_successful_trial_of_labor_after_cesarean_deliveryevaluation_of_two_scoring_systems.pdf
  • https://pmc.ncbi.nlm.nih.gov/articles/PMC6626212/
  • https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2021/12/counseling-regarding-approach-to-delivery-after-cesarean-and-the-use-of-a-vaginal-birth-after-cesarean-calculator

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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