(121) Antenatal Corticosteroid Exposure in Late Preterm Small for Gestational Age: A Population Cohort Study

Objective: To examine outcomes in parturients who delivered a small for gestational age (SGA) newborn in the late preterm period and who either received antenatal corticosteroids (ANCS) or did not.

Study Design: This population-based retrospective cohort study used U.S. Vital Statistics dataset (2016-2020). The inclusion criteria were singleton, liveborn non-anomalous individuals delivering between 34.0 – 36.6 weeks' gestation with SGA neonate (birth weight < 10% for gestational age, Duryea EL et al) and known status of exposure to ANCS at any time in gestation. The primary outcome was a composite neonatal adverse outcome including Apgar score < 5 at 5 min, immediate assisted ventilation, assisted ventilation > 6 hrs., surfactant use, seizure, or neonatal mortality. Multivariable Poisson regression models were used to estimate adjusted relative risks (aRR) and 95% confidence intervals (CI). A subgroup analysis by gestational age was performed.  Annual percent change (APC) was calculated to assess changes in rates of ANCS exposure over study period.

Results: Of 19 million live births during the study period, 109,985 (0.6%) met inclusion criteria, and among them, 26,151 (24%) individuals with SGA neonates received ANCS. After adjustment, the composite neonatal adverse outcome, mainly driven by respiratory complications, was higher among those who received ANCS than those who did not (aRR 1.31, 95% CI 1.27-1.35). This difference persisted in gestational age subgroup analysis at 34 (aRR 1.35, 95% CI 1.29 – 1.42), 35 (aRR 1.27, 95% CI 1.21 – 1.35) and 36 weeks' gestation (aRR 1.31, 95% CI 1.24 – 1.38). The rate of ANCS exposure remained stable over the 5 years period (APC 14.2 95% CI -1.1 – 31.9).

Conclusion: Among individuals with late preterm neonates and small for gestational age, 1 out of 4 had exposure to antenatal corticosteroids, and it was associated with a higher risk of neonatal morbidity.