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To compare maternal and neonatal outcomes among large-for-gestational-age neonates with and without prenatal ultrasound suspicion of large-for-gestational-age.

We conducted a population-based retrospective cohort study of term large-for-gestational-age births in Ontario, Canada (2012–2021) using linked health administrative data. Outcomes included labour interventions, maternal complications, and neonatal outcomes. Propensity scores with overlap weights were applied in modified Poisson regression models.

Among 82,359 large-for-gestational-age births, 3,969 (4.8%) had prenatal ultrasound suspicion of large-for-gestational-age. After adjustment, suspected large-for-gestational-age had higher rates of induction (aIRR [adjusted incidence rate ratio] 1.48, 95% CI 1.44–1.52), planned cesarean (2.76, 2.54–3.00), unplanned cesarean (1.40, 1.33–1.48), postpartum hemorrhage (1.16, 1.06–1.27), shoulder dystocia (1.10, 1.02–1.19), and neonatal intensive care unit admission (1.33, 1.23–1.43). Operative vaginal delivery and obstetric trauma rates were lower among deliveries with suspected large-for-gestational-age (0.69, 0.61–0.79 and 0.83, 0.72–0.96 respectively). In sensitivity analyses 1) removing gestational hypertension variables from the propensity score and 2) including those without a documented complication of suspected-large-for-gestation-age but a late third trimester ultrasound to the exposed group, results were similar to the main analysis.

Prenatal ultrasound suspicion of large-for-gestational-age is associated with altered management but does not reduce cesarean delivery or shoulder dystocia but is effective in reducing operative vaginal delivery and obstetric trauma in a cohort of confirmed large-for-gestational-age births. Sensitivity analyses accounting for potential mediating factors and misclassification bias further supported the above findings.