Induction of Labor in Nulliparas: Comparative Outcomes by Indication

Abstract To evaluate obstetric and neonatal outcomes among nulliparous patients undergoing induction of labor (IOL) for different clinical indications. This retrospective cohort study included singleton nulliparas at ≥ 37 weeks’ gestation with intact membranes and an unfavorable cervix who underwent IOL at a single academic center over seven years. Participants were categorized by indication: (1) placental complications (hypertensive disorders, fetal growth restriction, abruption, oligohydramnios), (2) diabetes mellitus (DM), (3) isolated fetal macrosomia, (4) prolonged pregnancy (≥ 41 weeks), (5) reduced fetal movements (RFM), (6) non-reassuring fetal heart rate (NRFHR), (7) multiple indications (≥ 2 of the above), and (8) elective IOL (control). Outcomes were compared between each group and the control. Multivariable logistic regression was performed, with Holm–Bonferroni adjustment for multiple comparisons. Among 2582 IOLs, 489 were elective, 447 for placental complications, 194 for DM, 54 for isolated macrosomia, 790 for prolonged pregnancy, 98 for RFM, 97 for NRFHR, and 413 for multiple indications. Isolated macrosomia was associated with higher total CD rates and CD due to labor arrest. NRFHR at presentation was associated with subsequent CD and intervention due to NRFHR, while placental-related and multiple-indication IOLs were associated with intervention due to NRFHR. DM and multiple-indication IOLs were associated with the composite neonatal adverse outcome. In multivariable analyses, isolated macrosomia remained strongly associated with CD due to labor arrest (aOR 5.18, 95% CI 2.65–10.11; Holm-adjusted p < 0.007), while DM and multiple indications were associated with the composite neonatal outcome (aOR 2.06 and 1.81, respectively). Among nulliparous patients undergoing IOL, obstetric and neonatal outcomes differed according to the indication for induction. These findings provide indication-specific prognostic information for counseling and intrapartum preparedness but should not be interpreted as comparing the safety of IOL with expectant management.