841: Late preterm antenatal corticosteroids and neonatal morbidity and mortality: estimating population-level absolute risk measures

Abstract

Randomized trial evidence suggests administration of antenatal corticosteroids (ACS) in the late preterm period (34-36 weeks) reduces neonatal respiratory complications. However, the risk-benefit tradeoff is less clear than in earlier gestational ages because baseline risks of adverse outcomes are lower, which may increase the number needed to treat (NNT) and decrease absolute risk reductions (ARRs) from week to week. Estimates of ARRs and NNTs based on population baseline rates of neonatal morbidity and mortality in the US population are critical for clinical counseling but are not readily available. Our objective was to generate these absolute risk estimates associated with ACS administration in late preterm gestations. We conducted a retrospective cohort study of births at 34-36 weeks’ gestation in the United States in 2012 and 2013 using the US Linked Birth-Infant Death records (CDC). Neonates were excluded if their mothers received ACS. Outcomes were neonatal death, NICU admission, assisted ventilation, and surfactant use. We applied relative risk estimates from recent randomized controlled trials to baseline risks in the US population to generate ARRs and NNTs with 95% confidence intervals for neonatal morbidity associated with ACS administration, stratified by gestational week at birth. There were 543,259 late preterm births in the United States in 2012-2013. ARRs for neonatal mortality and morbidities decreased with advancing gestational age, and NNTs increased (Figures 1 and 2). At 34 weeks’ gestation, 31 (95% CI, 20-85) pregnant women would need to be treated with ACS to prevent one assisted ventilation; at 36 weeks, the number was 83 (54-229). Likewise, the NNT for surfactant use was 123 (77-4796) at 34 weeks and 518 (326-20212) at 36 weeks. Our estimates of absolute risk measures derived from population baseline risks of neonatal morbidities are generalizable to the general obstetrical population. These absolute risk measures may be more useful for patient counseling and clinical decision making than relative risks from randomized trial populations alone.View Large Image Figure ViewerDownload Hi-res image Download (PPT)