Preterm lung function after retreatment with antenatal betamethasone in preterm lambs.

Abstract

We hypothesized that two doses of betamethasone administered 1 week apart would further enhance postnatal pulmonary function in preterm lambs (compared with a single dose). Fetal sheep (121 days' gestation) randomly received saline solution or betamethasone (0.5 mg/kg) as a single injection. Six days later fetal sheep were retreated with either saline solution or corticosteroid, and postnatal lung function was evaluated 1 day later. Betamethasone improved compliance and ventilation efficiency index nearly 50%, and total lung volume increased twofold. No effects of treatment-to-delivery interval (1 vs 7 days) or corticosteroid retreatment on pulmonary function were apparent. Although surfactant pool sizes increased as a function of duration of exposure, no additional effect of corticosteroid retreatment was noted. Antenatal betamethasone increased messenger ribonucleic acid levels for the surfactant proteins A and C, and retreatment augmented surfactant protein B messenger ribonucleic acid levels but suppressed surfactant protein A and C messenger ribonucleic acid. Improved postnatal lung function resulting from antenatal betamethasone was not augmented by retreatment.