Work

Association of sonographic estimated fetal weight with primary cesarean delivery after adjustment for neonatal birthweight in term nulliparous pregnancies

Year: 2026

Type: article

Abstract: Objective To examine whether a relatively higher prenatal sonographic estimated fetal weight (EFW), compared with the newborn's eventual birthweight, is associated with primary cesarean delivery among term nulliparous pregnancies. Methods We conducted a single-center retrospective cohort study at Vinmec Times City International Hospital between January and September 2024. Eligible women were nulliparous with singleton, cephalic, term pregnancies, entered spontaneous labor or underwent induction of labor, and had sonographic EFW recorded within 7 days of delivery. The linear association between EFW and neonatal birthweight was described using Pearson correlation, while agreement was assessed using signed error, mean absolute percentage error (MAPE), the proportion within ±10% of birthweight, and Bland-Altman analysis. The primary modified Poisson model examined EFW–birthweight discrepancy while accounting for neonatal birthweight and adjusting for maternal age, gestational age at delivery, fetal sex, and scan-to-delivery interval. Results Among 353 women, 168 (47.6%) underwent cesarean delivery. Mean EFW was 3,205 ± 267 g and mean neonatal birthweight was 3,178 ± 314 g. Prenatal EFW and neonatal birthweight were positively correlated (Pearson r = 0.78). Mean signed error was +27.1 g, MAPE was 5.15%, and 89.0% of estimates were within ±10% of birthweight. In the primary linear model, each 100-g greater EFW–birthweight discrepancy was associated with an 11% higher risk of cesarean delivery after accounting for neonatal birthweight and prespecified covariates (adjusted risk ratio [aRR] 1.11, 95% CI 1.04–1.20; p = 0.003). Findings were consistent across prespecified sensitivity analyses (aRR range, 1.11–1.14). Conclusion Among term nulliparous women, a relatively higher prenatal sonographic EFW compared with eventual neonatal birthweight was associated with a higher risk of primary cesarean delivery. This association should not be interpreted as evidence that knowledge of EFW caused cesarean delivery and should be considered in light of residual confounding and individual-level uncertainty in EFW.

Source: Frontiers in Medicine

DOI: 10.3389/fmed.2026.1989181