(536) Betamethasone Exposure Among Term Newborns Following Recommendation for Late Preterm Antenatal Corticosteroids

Objective: Since the Antenatal Betamethasone for Women at Risk for Late Preterm Delivery (ALPS) Trial, antenatal corticosteroids (ACS) have become standard of care for patients at risk of late preterm delivery. Emerging data suggest term newborns exposed to preterm ACS are at increased risk of adverse outcomes. We aim to compare betamethasone exposure among term newborns before and after implementation of late preterm ACS.

Study Design: We conducted a cohort study of singleton live born term deliveries within a regional hospital system between 1/2013-3/2019. Deliveries were classified as pre- and post-ALPS, matched 1:2 in sequential fashion. Pre-ALPS deliveries occurred between 1/2013-4/2016; post-ALPS deliveries occurred between 4/2017-3/2019 with a 1-year post-publication washout. Exclusions were dexamethasone recipients and missing delivery data. The primary outcome was betamethasone exposure among term newborns. Secondary outcomes included neonatal intensive care unit (NICU) admission and small for gestational age (SGA). Analyses were performed with student’s T test and chi-square test.

Results: Among 20,460 term deliveries, 6,820 were pre-ALPS and 13,640 were post-ALPS. Baseline characteristics were similar. Post-ALPS term neonates had increased exposure to betamethasone compared to pre-ALPS infants (3.1% versus 1.2%, OR 2.6, 95% CI 2.0-3.3). The percentage of pregnancies exposed to betamethasone that subsequently delivered at term increased with advancing gestational age at administration (figure). Among term-born neonates, 315 received ACS before 34 weeks, 190 after 34 weeks and 19,938 were ACS unexposed. SGA was most common in the ACS < 34 week group (11.4%) followed by the ≥ 34 week group (11.0%) and then unexposed neonates (6.1%, p< 0.001). Similarly, NICU admission was highest among < 34 week infants followed by late preterm ACS and unexposed, respectively (6.0% vs 4.7% vs 2.6%, p< 0.01).

Conclusion: Implementation of late preterm ACS correlated with substantially increased risk for betamethasone exposure among term-born neonates, potentially increasing both short- and long-term morbidity.