Decreased respiratory compliance in infants less than or equal to 32 weeks' gestation, delivered more than 7 days after antenatal steroid therapy.

OBJECTIVES: Our objective was to compare the pulmonary function (respiratory compliance) of infants who were < or = 32 weeks' gestation and delivered > 7 days after a single course of antenatal steroids versus infants who were delivered 1 to 7 days after a single course of antenatal steroids.
METHODS: A prospective cohort study of respiratory system compliance was conducted of infants < or = 32 weeks' gestation within 72 hours of life and before surfactant therapy if needed. The study (remote) group was composed of infants who were treated with antenatal steroids > 7 days before delivery and the comparison group (ideal group) of matched infants who were treated with antenatal steroids 1 to 7 days before delivery. Respiratory system compliance was measured with the single-breath occlusion technique.
RESULTS: Twenty-eight remotely treated infants and 28 ideally treated infants were studied. The remote group had a significantly lower respiratory system compliance per kilogram and total respiratory system compliance when compared with the ideal antenatal steroids group. Within the remote group, infants who received antenatal steroids 8 to 14 days (n = 10) before delivery had a significantly higher respiratory system compliance and a trend to less surfactant need (10% vs 33%) as compared with infants who received antenatal steroids > 14 days (n = 18) before delivery.
CONCLUSIONS: Infants who were < or = 32 weeks' gestation and remotely treated with antenatal steroids (average 21 days) had a significantly lower respiratory compliance compared with matched infants who were ideally treated with antenatal steroids. We speculate that the lower respiratory system compliance may reflect the dissipation of beneficial effects of antenatal steroids on pulmonary function when delivery occurs > 7 days after therapy and particularly when therapy is > 14 days before delivery.