Timing of antenatal corticosteroid administration and survival in extremely preterm infants : A national population-based cohort study

Objective: To explore the association between administration-to-birth interval of antenatal corticosteroids (ACS) and survival in extremely preterm infants. Design: Population-based prospective cohort study. Setting: All obstetric and neonatal units in Sweden from 1 April 2004 to 31 March 2007. Population: All live-born infants (n = 707) born at 22-26 completed weeks of gestation. Methods: The relationship between time from first administration of ACS to delivery and survival was investigated using Cox proportional hazards regression analysis. Main outcome measures: Neonatal (0-27 days) and infant (0-365 days) survival, and infant survival without major neonatal morbidity (intraventricular haemorrhage grade ≥ 3, retinopathy of prematurity stage ≥ 3, periventricular leukomalacia, necrotising enterocolitis, or severe bronchopulmonary dysplasia). Results: Five-hundred and ninety-one (84%) infants were exposed to ACS. In the final adjusted model, infant survival was lower in infants unexposed to ACS [hazard ratio (HR) = 0.26; 95% confidence interval 0.15-0.43], in infants born 7 days after ACS [HR = 0.56 (0.32-0.97)], but not in infants born 24-47 h after ACS [HR = 1.60 (0.73-3.50)], as compared with infants born 48 h to 7 days after administration. The findings were similar for neonatal survival. Survival without major neonatal morbidity among live-born infants was 14% in unexposed infants and 30-39% in steroid-exposed groups, indicating that any ACS exposure was valuable. Conclusions: Administration of ACS 24 h to 7 days before extremely preterm birth was associated with significantly higher survival than in unexposed infants and in infants exposed to ACS at shorter or longer administration-to-birth intervals. Tweetable abstract: Timing of antenatal corticosteroids is important for extremely preterm infants' survival