Introduction
First introduced by Liggins and Howie in 1972,1administration of a single course of antenatal corticosteroids (ACS) to women at risk of preterm birth between 24 and 34 weeks gestation, has been shown to significantly reduce infant morbidity and mortality.2 3 Nevertheless, translation of this knowledge into clinical practice has been less than ideal: population-based studies show that rates of any ACS use ranged from 65% among deliveries at 24-27 weeks, to 79% among deliveries at 28-32 weeks and 50% of deliveries at 33-34 weeks’ gestation in Canadian settings in 2008-12.4 5 Rates of optimal ACS prophylaxis were significantly lower, and these rates reflect the challenges associated with accurate prediction of preterm delivery, differences in international guidelines, and inconsistencies in clinical practice.6 An added concern is the significant rate of ACS administration among women who go on to deliver at term gestation.4
In recent years there has been a re-evaluation of the upper gestational age limit for ACS prophylaxis following the Maternal Fetal Medicine Units Network Antenatal Late Preterm Steroids trial (ALPS) in 2016.7 The ALPS study, which was a double-blind, placebo-controlled, randomized trial published in April 2016, showed that administration of ACS to women at risk for delivery at late preterm gestation (i.e., 34+0 to 36+6 weeks) significantly reduces the rate of neonatal respiratory complications.7 In response, the American College of Obstetricians and Gynecologists (ACOG)8 and the Society for Maternal-Fetal Medicine (SMFM)9 altered their guidance regarding ACS administration to include women at risk of late preterm delivery. However, the higher rates of hypoglycemia following ACS therapy at late preterm gestation,7 (potentially leading to longer-term risks of developmental delay),10 and the paucity of rigorous follow-up studies regarding the long-term effects of ACS exposure in late-preterm infants,10 led several experts11 12 to advise against ACS administration in the late preterm period. The 2018 Canadian guideline from the Society of Obstetricians and Gynaecologists of Canada (SOGC) also did not support initiation of ACS therapy at 35 and 36 weeks gestation.13
Given the existing evidence and conflicting guidelines, it is unclear how clinical practice has changed with regard to ACS prophylaxis for women at risk of late preterm delivery. We carried out a study to investigate how the ALPS trial findings, and the recent ACOG, SMFM and SOGC guidelines, have been translated into clinical practice in Canada and the United States. We also assessed rates of optimal and suboptimal trends in ACS use.