Antenatal corticosteroids beyond 34 weeks gestation: What do we do now?

The practice of antenatal corticosteroid administration in pregnancies of 24-34 weeks of gestation that are at risk of preterm delivery was adopted over 20 years after the first randomized clinical trial in humans. It is biologically plausible that antenatal corticosteroid in pregnancies beyond 34 weeks of gestation would reduce rates of respiratory morbidity and neonatal intensive care admission. Mostly guided by the results of a large multicenter randomized trial of antenatal corticosteroid in late preterm infants, the Antenatal Late Preterm Steroids Trial, the American Congress of Obstetricians and Gynecologists has released a practice advisory that the "administration of betamethasone may be considered in women with a singleton pregnancy between 34 0/7 and 36 6/7 weeks of gestation at imminent risk of preterm birth within 7 days." However, many unanswered questions about the risks and benefits of antenatal corticosteroids in this population remain and should be considered with the adoption of this treatment recommendation. This review of the literature indicates that the greatest effect is in the reduction of transient tachypnea of the newborn infant, which is a mostly self-limited condition. This benefit must be weighed against unanticipated outcomes, such as neonatal hypoglycemia, and unknowns about long-term neurodevelopmental follow up and metabolic risks. Amelioration of respiratory morbidity in late preterm infants does not preclude these infants from having other complications that are related to prematurity that require intensive care. Other possible morbidities of prematurity may be magnified if these babies no longer have respiratory symptoms. Conversely, if these late preterm babies no longer exhibit respiratory symptoms and "look good," they may be discharged before other morbidities of prematurity have resolved and be at risk for readmission. Furthermore, it is also important to ensure that unintended consequences are avoided to achieve a minor benefit. Some of these consequences may include treatment with multiple steroid courses or "treatment creep" in women at 34 to < 37 weeks of gestation who do not meet the inclusion/exclusion criteria of the Antenatal Late Preterm Steroids Trial, particularly when a high percentage of women do not receive antenatal corticosteroid within 7 days of delivery. Finally, we believe that caution should be exercised before wide-scale universal adoption of antenatal corticosteroid for pregnancies that are at risk of preterm birth at 34 to < 37 weeks of gestation, when it is unclear whether there are long-term effects. For a more balanced rationale for the decision to use antenatal corticosteroid treatment in pregnancies at > 34 weeks of gestation, we urge for ongoing research into the risks and benefits of antenatal corticosteroid use in preterm infants overall, for better prediction of preterm birth so that antenatal corticosteroid can be administered within the ideal time frame, and for long-term neurodevelopmental follow-up of the participants in the large randomized Antenatal Late Preterm Steroids Trial.