Antenatal Betamethasone for Women at Risk for Late Preterm Delivery

Infants who are born at 34 to 36 weeks of gestation (late preterm) are at greater risk for adverse respiratory and other outcomes than those born at 37 weeks of gestation or later. It is not known whether betamethasone administered to women at risk for late preterm delivery decreases the risks of neonatal morbidities.

We conducted a multicenter, randomized trial involving women with a singleton pregnancy at 34 weeks 0 days to 36 weeks 5 days of gestation who were at high risk for delivery during the late preterm period (up to 36 weeks 6 days). The participants were assigned to receive two injections of betamethasone or matching placebo 24 hours apart. The primary outcome was a neonatal composite of treatment in the first 72 hours (the use of continuous positive airway pressure or high-flow nasal cannula for at least 2 hours, supplemental oxygen with a fraction of inspired oxygen of at least 0.30 for at least 4 hours, extracorporeal membrane oxygenation, or mechanical ventilation) or stillbirth or neonatal death within 72 hours after delivery.