The frequency of prior antenatal corticosteroid therapy in late preterm birth pregnancies.

We sought to quantify how often women with late preterm birth (LPTB) receive antenatal corticosteroid (ACS) therapy prior to 34 weeks and to determine its effects on neonatal respiratory morbidity. LPTBs (34 (0)/ (7) to 36 (6)/ (7) weeks) over a 1-year period at a single tertiary care hospital were studied. A composite neonatal respiratory outcome was defined as mechanical ventilation, continuous positive airway pressure with fraction of inspired oxygen (F IO(2)) >40% for >2 hours or F IO(2) >40% for >4 hours within the first 72 hours of life. Multivariate logistic regression analysis was used to evaluate the association between ACS therapy and neonatal respiratory morbidity. Over the study period, 503 LPTBs met the study criteria and 6.8% ( N = 34) had ACS therapy <34 weeks. Most had exposure >7 days prior to delivery (64.7%). Almost one-half of those receiving prior ACS therapy delivered between 34 and 35 weeks. There was no difference in the rate of prior ACS therapy based on LPTB indication for delivery. After adjusting for confounding factors, prior ACS therapy was not associated with lower respiratory morbidity (odds ratio [OR] 2.0, 95% confidence interval [CI] 0.2 to 16.3, P = 0.53). Advancing gestational age was the only variable associated with respiratory morbidity (OR 0.50, 95% CI 0.26 to .94, P = 0.03). In our population, prior ACS therapy was infrequent and was not associated with improvements in neonatal respiratory morbidity following LPTB.