We investigated the effects of intra-amniotic (IA) betamethasone or budesonide injections on lung structure 2 or 7 d after treatment in preterm fetal sheep. Pregnant ewes received intra-amniotic betamethasone (2 mg/kg fetal weight), budesonide (2 mg/kg), saline or maternal intramuscular betamethasone (0.5 mg/kg maternal weight), or saline. Lambs were delivered 2 or 7 d later at 124 d of gestation. Morphometric analysis was conducted on the right upper lung lobe. Intra-amniotic corticosteroids, 2 or 7 d before delivery, resulted in higher average alveolar volumes than controls (2 d: 25 -35 , 7d: 15 -25 ). All corticosteroid treatments resulted in thinning of alveolar walls 7 d after treatment and a higher proportion of alveolar ducts and a lower alveolar wall fraction relative to controls 2 or 7 d after treatment. The changes in structural lung indices correlated with the improved lung function at 2 d. Structural lung indices and increased surfactant correlated with the improved lung function at 7 d. Similar structural changes induced by intra-amniotic corticosteroids and maternal intramuscular betamethasone were associated with improvements in lung function at 2 and 7 d.
Polglase, G., Nitsos, I., Jobe, A., Newnham, J., & Moss, T. (2007). Maternal and intra-amniotic corticosteroid effects on lung morphometry in preterm lambs. Pediatric Research, 62(1), 32 - 36. https://doi.org/10.1203/PDR.0b013e3180686433