Effectiveness of Antenatal Corticosteroids in Reducing Respiratory Disorders in Late Preterm Infants: Randomized Clinical Trial

Late preterm infants are at increased risk of transient tachypnea of the newborn, respiratory distress syndrome, and other respiratory disorders. Such late preterm infants as well as preterm infants born before 34 weeks of gestation often require oxygen and ventilatory support and admission to neonatal intensive care units. Antenatal treatment with corticosteroids accelerates lung maturation in preterm infants. The benefits of antenatal treatment with corticosteroids before 34 weeks of pregnancy are well established, but it is unclear whether these effects extend to late preterm term infants born after 34 weeks of gestation. This randomized triple-blind trial conducted in Brazil evaluated the effectiveness of treatment with antenatal corticosteroids at 34 0/7 to 36 6/7 weeks of pregnancy in reducing the incidence of neonatal respiratory disorders among women at risk of imminent premature delivery. The primary study outcome measure was the occurrence of neonatal respiratory disorders (respiratory distress syndrome or transient tachypnea of the newborn). Secondary outcomes included neonatal morbidity (any respiratory complications or other morbidity), need for ventilatory support, and duration of stay in hospital. A total of 320 women were randomized to receive intramuscular doses of betamethasone 12 mg (n = 163) or placebo (n = 157) for 2 consecutive days. The final analysis included 144 women in the corticosteroid group and 130 in the placebo group. There was no difference between the groups in the rates of respiratory distress syndrome (1.4% [2 subjects] in the corticosteroid group vs. 0.8% [1 subject] in the placebo group; P = 0.54) or rates of transient tachypnea of the newborn (24% [34 subjects] in the steroid group vs. 22% [29 subjects] in the placebo; P = 0.77). Corticosteroid treatment did not reduce the risk of respiratory morbidity at 34, 35, and 36 or more weeks of gestation; the risk of respiratory morbidity after adjustment for gestational age was 1.12, with a 95% confidence interval of 0.74 to 1.70. No difference was found between the steroid and placebo groups in the need for ventilatory support (19% vs. 20%), outcomes for neonatal morbidity (62%, n = 88 vs. 72%, n = 93; P = 0.08), or in the duration of stay in hospital (5.12 vs. 5.22 days; P = 0.87). The rate of jaundice requiring phototherapy was lower among babies whose mothers had received corticosteroids ([24%, n = 34] vs. 38% [n = 49]; the risk ratio was 0.63, with a 95% confidence interval of 0.44–0.91; P = 0.01). These findings suggest that antenatal treatment with corticosteroids at 34 to 36 weeks of gestation is not associated with a significant reduction in the incidence of neonatal respiratory disorders among preterm infants.