A clinical decision making model for NTSV deliveries

ObjectiveTo evaluate modifiable antepartum and intrapartum factors associated with nulliparous, term, singleton, vertex (NTSV) cesarean delivery and to model risk stratified induction timing strategies that minimize cesarean risk across maternal risk profiles. Study DesignThis retrospective cohort study included all NTSV deliveries at a tertiary care center from January 2015 through August 2025 (overall cohort n=10,525; limited risk cohort n=5,663). Machine learning identified key predictors of cesarean delivery, with maternal age and pre pregnancy body mass index (BMI) used to define low, moderate, and high risk strata. Logistic regression estimated the association between induction and cesarean delivery, and a Monte Carlo simulation compared elective induction at 39, 40, or 41 weeks versus expectant management to 42 weeks within each stratum. ResultsCesarean delivery occurred in 20.1% of the overall cohort and 19.0% of the limited risk cohort, with a U shaped relationship between gestational age and cesarean risk and lowest rates at 38-39 weeks. Induction was associated with higher cesarean rates than spontaneous labor in both cohorts (overall: 24.1% vs. 17.1%; limited risk: 22.9% vs. 15.7%) after adjustment for age, BMI, and gestational age. No single induction policy minimized cesarean risk across all strata. For high risk patients (age >=35 years and BMI >=35), induction at 39 weeks yielded the lowest modeled cesarean rate, whereas later delivery (40 to 41 weeks or expectant management to 41 weeks) was favored for low and moderate risk patients. A universal 39 week induction policy for low and moderate risk strata modestly increased modeled cesarean rates, adding an estimated 46 cesarean deliveries. ConclusionGestational age at delivery and induction strategy are key modifiable determinants of NTSV cesarean delivery, but optimal timing varies by maternal age and BMI risk profile, supporting risk stratified rather than universal 39 week induction policies.