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.