What’s the best way to predict the success of a trial of labor after a previous C-section?

Hashima and Guise: A 3-point scoring tool

Hashima and Guise evaluated 16 variables and identified 7 associated with TOLAC outcome: indication for cesarean delivery (recurrent vs nonrecurrent), chorioamnionitis, macrosomicinfant, age, anemia, diabetes, and infant sex, from which they created a 3-point scoring tool using the variables most associated with TOLAC outcome. Each variable was assigned a score of 0 or 1, and the likelihood of TOLAC success was calculated.¹⁰

They found a relationship between score and TOLAC success. The original study population of 10,828 was randomly divided into a score development and validation group. TOLAC success percentages were most discordant between the tool development and internal validation groups for score 0 at 7%. Scores 1 to 3 were within 4% of each other.

ACOG lists strong predictors of a successful vaginal birth after cesarean as previous vaginal birth and spontaneous labor.

Schoorel: A model designed for Western Europeann women

Finally, Schoorel et al developed and internally validated a prediction model for a Western European population, to be used during counseling in the third trimester of pregnancy.¹¹ Six variables were identified and entered into the model calculations: prepregnancy BMI (entered as a continuous variable), (OR=0.96; 95% CI, 0.92-1.00); previous cesarean for nonprogressive labor (OR=0.50; 95% CI, 0.33-0.76); previous vaginal delivery (OR=3.81; 95% CI, 2.10-6.92); induction of labor (OR=0.52; 95% CI, 0.33-2.10); estimated fetal weight >90th percentile (OR=0.54; 95% CI, 0.14-2.02); and white ethnicity (OR=1.61; 95% CI, 0.97-2.66). The authors noted that the predicted probability of TOLAC success ranged from 39% to 93%, with a mean of 72% (standard deviation, 11%), and only noted the predicted probabilities were well calibrated from 65% upwards without additional data on specific performance.

RECOMMENDATIONS

The American College of Obstetricians and Gynecologists (ACOG) lists strong predictors of a successful vaginal birth after cesarean as previous vaginal birth and spontaneous labor. Factors associated with decreased probability of success are recurrent indication for initial cesarean delivery (labor dystocia), increased maternal age, nonwhite ethnicity, gestational age greater than 40 weeks, maternal obesity, preeclampsia, short interpregnancy interval, and increased neonatal birth weight. ACOG does not offer any weighted or risk-based scoring tools for predicting success.¹³

Neither the American Academy of Family Physicians nor the American College of Nurse Midwives recommend specific scoring tools or success predictors.