Ureaplasma colonization of amniotic fluid and efficacy of antenatal corticosteroids for preterm lung maturation in sheep

Objective: To assess the efficacy of maternal betamethasone for improving preterm lung function, in the presence of inflammation induced by amniotic fluid ureaplasma colonization. ----- ----- Study design: Ewes bearing single fetuses were randomized to receive an intra-amniotic injection of Ureaplasma parvum (serovar 6; 2×107 colony forming units) or vehicle at 86±2 days of pregnancy (mean±SD: term is 150d), followed by maternal intramuscular betamethasone (0.5mg/kg) or saline, either 2 or 7 days before delivery of lambs at 123±1d. ----- ----- Results: Amniotic fluid IL-8 was elevated by ureaplasmas (p=0.049) but unaffected by betamethasone. Lung inflammation induced by ureaplasmas was not affected by betamethasone. Lung compliance was increased by ureaplasma colonization (p=0.009) and betamethasone (p=0.042), and effects were additive. Lung surfactant was increased by ureaplasma colonization (p<0.001) and betamethasone 7 days (p=0.001), but not 2 days, before delivery. ----- ----- Conclusion: Inflammation improves preterm lung function due to increases in surfactant. Antenatal corticosteroids further augment lung function, through an apparently independent mechanism.