Development and validation of a predictive nomogram for cesarean delivery in term singleton pregnancies complicated by small for gestational age undergoing labor induction

To identify antenatal and post-ripening factors associated with cesarean delivery in term singleton pregnancies complicated by small for gestational age (SGA) undergoing induction of labor, and to develop and internally validate a predictive nomogram intended for post-ripening dynamic risk assessment. We conducted a retrospective cohort study of 507 women with term singleton pregnancies whose neonates were retrospectively confirmed as SGA (birth weight below the 10th percentile for gestational age and sex) and who underwent induction of labor at Fujian Maternity and Child Health Hospital between October 2017 and December 2022. The cohort was randomly split into a derivation cohort (n = 354, 70%) and an internal validation cohort (n = 153, 30%). The primary outcome was cesarean delivery after induction of labor, irrespective of indication. Univariable and multivariable logistic regression were used to identify independent factors associated with the outcome, and a nomogram was developed in the derivation cohort and assessed in the internal validation cohort. Cesarean delivery after induction of labor occurred in 134 (26.4%) women. Four factors were independently associated with the outcome: maternal age (aOR 1.08, 95% CI 1.01-1.15), admission weight (aOR 1.04, 95% CI 1.01-1.07), induction with dinoprostone versus a Cook double balloon (aOR 2.08, 95% CI 1.13-3.81), and Bishop score after cervical ripening (aOR 0.65, 95% CI 0.54-0.80). The nomogram showed an area under the receiver operating characteristic curve of 0.78 (95% CI 0.73-0.84) in the derivation cohort and 0.77 (95% CI 0.68-0.86) in the internal validation cohort, with adequate calibration (Hosmer-Lemeshow P = 0.397 and 0.812, respectively) and clinical net benefit on decision curve analysis. Among term singleton pregnancies with SGA already undergoing induction of labor, the proposed nomogram may support post-ripening dynamic risk assessment for cesarean delivery and serve as an adjunct to clinical judgment for counseling, intrapartum surveillance, and perinatal preparedness. External validation in independent multicenter cohorts is warranted.