941 Single betamethasone dose for late prematurity and neonatal morbidity

Although the standard regimen for late preterm birth (LPTB) antenatal corticosteroids involves two doses of betamethasone given 24 hours apart, not all women remain pregnant long enough to receive a second dose. We sought to compare neonatal morbidity among individuals at risk of LPTB following a single dose of betamethasone (BMZ) versus placebo. We performed a secondary analysis of the ALPS trial (Gyamfi-Bannerman C. et al., NEJM; PMC4823164). All individuals enrolled in the parent trial that received a single dose of either BMZ or placebo were included. Individuals with randomization-to-delivery interval > 24 hours were excluded. Primary outcome was a composite of respiratory support at 72 h, including continuous positive airway pressure or high flow nasal cannula ≥ 2 h, oxygen with an inspired fraction of ≥ 30% for ≥ 4 h, or mechanical ventilation. Of the 2,831 individuals in the parent trial, 1,083 (38%) met inclusion criteria; of them 539 (50%) received BMZ. The placebo and BMZ groups had similar clinical characteristics; rates of premature rupture of membranes (41% vs. 43%), spontaneous labor (50% vs. 50%), and cesarean delivery (18% vs. 17%) did not differ between groups. Age and race were balanced as well. Table 2 describes neonatal outcomes for the study population. Compared to placebo, the primary respiratory outcome was not lower among those who received a single BMZ dose (aRR 1.10, 95% CI 0.84-1.46). Furthermore, a single dose of BMZ was associated with neonatal hypothermia compared to placebo (aRR 1.55, 95% CI 1.07-2.26). Stratification by randomization-to-delivery intervals of 12-hour increments also showed no differences between groups. In individuals with LPTB pregnancies who received betamethasone and delivered prior to a second dose, there were no differences in neonatal respiratory morbidities compared to placebo. Our analysis supports the concept that the optimal timing of benefit for BMZ is greater than 48 hours of administration.