Antenatal associations with lung maturation and infection.

Chronic clinically unapparent chorioamnionitis is a common antenatal exposure for very preterm infants, and these infants have variable degrees of lung maturation and a high risk of developing bronchopulmonary dysplasia. Exposure of fetal sheep to intra-amniotic endotoxin or IL-1alpha induces chorioamnionitis and lung injury (decreased alveolarization and microvascular injury), which resolves to a phenotype of striking lung maturation (increased surfactant, improved gas exchange and lung mechanics). The immune responses of the fetus also are suppressed or induced (matured) in time and dose-dependent ways by either chorioamnionitis or antenatal corticosteroids. These experimental observations contribute to explanations of why preterm infants have variable degrees of lung maturation at birth and unpredictably develop bronchopulmonary dysplasia BPD.