Timing of antenatal corticosteroids and neonatal pulmonary mechanics

OBJECTIVE: We sought to compare lung mechanics in infants treated with mult iple courses of antenatal corticosteroids with those in matched control inf ants delivered >7 days from dosing and those of matched untreated infants. STUDY DESIGN: Eighteen infants who received multiple courses of corticoster oids and were delivered within 7 days of dosing were matched with 18 infant s who received 1 course of corticosteroids >7 days before delivery (remote) and 18 untreated infants. Respiratory compliance and functional residual c apacity were measured within 36 hours. Differences were compared by analysi s of variance. RESULTS: Infant demographics were similar. Respiratory compliance was highe r in the multiple-course group than in the remote or untreated group (P < . 02). Functional residual capacity was higher in the multiple-course group t han in the untreated group (P < .05) but similar to that found in the remot e group. CONCLUSION: Babies delivered after multiple courses of corticosteroids and within 7 days of dosing demonstrated improved respiratory compliance compar ed with untreated and remotely treated infants. This suggests that the enzy me system responsible for surfactant production can be repetitively induced despite prior treatment with corticosteroids. The increased functional res idual capacity in remotely treated infants may reflect a maturation of lung architecture independent of surfactant production.