Objectives: Antenatal corticosteroids are standard of care for women at risk of a preterm birth and demonstrated to be protective against poor outcomes in neonates including respiratory disorders, mortality and intraventricular hemorrhage (IVH). Its benefits may vary by gestational age, and accurate estimation is needed in a single-center population to account for practice variation.
Methods: A retrospective cohort of infants admitted to the hospital's neonatal intensive care unit, 1997-2015. Using Poisson regression, we separately modeled the incidence rate ratio of death, grade III or IV intraventricular hemorrhage (IVH), and moderate to severe bronchopulmonary dysplasia (BPD) testing the moderating effects of gestation on antenatal steroids, controlling for potential confounding.
Results: Among 5314 infants admitted, death occurred in 298 (6%), severe IVH in 244 (5%), and BPD in 527 (10%). Antenatal steroids were protective of death and BPD in the adjusted analysis, and there was multiplicative interaction where each week increase in gestational age combined with steroid therapy resulted in 13% reduced incidence for each outcome.
Conclusions for practice: Antenatal steroids are protective against severe IVH and moderate to severe BPD, and when combined with gestational age, steroids are associated with greater protective benefits in older neonates. There is likely an ideal window to maximize the benefits of antenatal steroids, and future etiologic research should consider the joint effects with gestational age.
Keywords: Antenatal steroids; Effect modification; Gestational age; Interaction.