472: Influence of the interval between antenatal corticosteroid administration and preterm labor on the occurrence of respiratory morbidity

Abstract

The aim of this study was to determine whether the effectiveness of a single complete course of antenatal corticosteroids (ACS) in the prevention of neonatal respiratory morbidity depends on the interval between ACS administration and delivery. A retrospective cohort study was performed in two perinatal centres among all women with threatened preterm labor who completed a single course of antenatal corticosteroids (betamethasone) before a gestational age of 34 weeks. We excluded women with a triplet pregnancy, women who delivered more than 21 days after completion of the ACS and antenatal deaths. Each neonate born from a twin pregnancy was analysed separately. We categorized the patients in three groups: ACS-delivery interval <7 days (1), between 7 and 14 days (2) and >14 days (3). Neonatal respiratory morbidity was defined as intubation of the neonate. We performed a logistic regression analysis to control for differences in gestational age at delivery. We included 254 neonates, of which 155 (61%) neonates were born <7 days after ACS, 64 (25%) neonates were born 7-14 days after ACS and 35 (14%) neonates were born >14 days after ACS. In total 76 (33%) neonates needed intubation. The risk for intubation in group 2 and group 1 was comparable (odds ratio 1.7 [95% CI 0.77-3.8]). However, neonates delivered >14 days after ACS (group 3) had an increased risk of needing intubation (odds ratio 4.6 [95% CI 1.6 – 14]). This effect was mainly found in the subgroup of neonates born between 28 and 32 weeks. As the effect of ACS administration is decreasing in time, administration of the first dose of ACS in women with threatened preterm labor should be considered carefully.