Timing of antenatal steroids exposure and its effects on neonates

Antenatal corticosteroid (ACS) has long been regarded as the standard of care for women at risk of preterm labour. There are, however, varying practices and regimes in ACS administration. It is unclear if "a window of efficacy" truly exists and if the benefits of ACS would diminish after 7 days from the first dose. The objective of this study is to determine if the time interval between antenatal corticosteroids and delivery influences the neonatal outcomes in preterm deliveries from 23⁺⁵ to 36⁺⁶ weeks' gestation.

This is a retrospective analysis of 302 women and 352 infants who delivered from 23⁺⁵ to 36⁺⁶ weeks' gestation in KK Women's and Children's Hospital from 1st November 2014 to 31st January 2015. The timings of the first two doses of corticosteroids and the delivery were retrieved. Neonatal outcomes were compared between those delivering within 7 days and those delivering beyond 7 days of first dose of ACS.

61.2% of preterm infants received at least one dose of antenatal corticosteroids, of which 23.6% received it within the window of efficacy. Overall incidence of respiratory distress asyndrome in our study is 17.6%. Significantly, neonates with ACS exposure beyond 7 days were seven times more likely to have RDS as compared to those exposed to ACS within the window of efficacy (RR 0.535, 95% CI 0.166-1.72), after adjusting for potential confounders.

The results of this study support the current practice among obstetricians to aim to administer ACS within 7 days of delivery.