Adverse perinatal outcomes associated with macrosomia in nulliparous women: A multicenter cohort study

Objective: Our study aimed to evaluate the combined risk of macrosomia and nulliparity. We investigated whether macrosomia is independently associated with an increased rate of intrapartum cesarean delivery (CD) and adverse maternal and neonatal outcomes among nulliparous women delivering at term. Methods: We conducted a retrospective cohort study including nulliparous women with singleton, term (37–42 weeks) deliveries between 2005 and 2024 at two university-affiliated medical centers in Jerusalem, Israel. Women who delivered macrosomic neonates (birth weight ≥4000 g) were compared with those delivering neonates weighing 3000–3500 g. Exclusions included multifetal gestations, preterm deliveries, elective cesareans, fetal anomalies, and antepartum demise. The primary outcome was intrapartum cesarean delivery. Secondary outcomes included a range of maternal and neonatal complications. Multivariable logistic regression was used to adjust for potential confounders including maternal obesity, pre-gestational diabetes, labor induction, and gestational age at delivery. Results: Among 86 801 eligible nulliparous women, 2762 (3.2%) delivered macrosomic neonates and 40 963 (47.2%) served as the control group. The rate of intrapartum CD was significantly higher among macrosomic deliveries compared to controls (18.6% vs. 7.8%, P < 0.01), though this association was not statistically significant after adjustment (adjusted odds ratio [aOR] 1.81, 95% confidence interval [CI]: 0.91–3.58). Macrosomia was independently associated with increased odds of shoulder dystocia (aOR 33.42, 95% CI: 11.32–98.68), postpartum hemorrhage (aOR 2.13, 95% CI: 1.79–2.54), blood transfusion (aOR 2.45, 95% CI: 1.51–3.98), chorioamnionitis (aOR 2.03, 95% CI: 1.57–2.61), neonatal intensive care unit admission (aOR 1.62, 95% CI: 1.15–2.29), neonatal hypoglycemia (aOR 2.23, 95% CI: 1.32–3.77), and Erb's palsy or clavicular fracture (aOR 9.43, 95% CI: 4.01–22.21). Stratification by birth weight categories revealed a dose–response relationship, with the highest complication rates among neonates >4500 g. Conclusion: In nulliparous women delivering at term, macrosomia is independently associated with a higher risk of multiple adverse maternal and neonatal outcomes. These findings underscore the compounded risk faced by nulliparous women with macrosomic fetuses and highlight the need for enhanced prenatal surveillance and individualized delivery planning in this population.