Ultrasound suspicion of fetal large for gestational age: A population-based cohort study using propensity score...

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.