Antenatal betamethasone improves postnatal transition in late preterm lambs with persistent pulmonary hypertension of the newborn

BACKGROUND: Persistent pulmonary hypertension of the newborn (PPHN) is associated with increased oxidative stress in pulmonary arteries (PA). Betamethasone decreases the oxidative stress and improves anti-oxidant balance in PPHN. We investigated whether antenatal betamethasone improves pulmonary vasodilation and postnatal oxygenation in late preterm lambs with PPHN. METHODS: PPHN was induced by constriction of fetal ductus arteriosus from 128 to 136d gestation. Ewes were given 2 i.m. doses of betamethasone or saline at 24h and 12h before Cesarian-section delivery at 136d gestation, simulating late preterm birth. Newborn lambs were mechanically ventilated for 8h with monitoring of blood gas and hemodynamic variables. Lungs were harvested post mortem to determine oxidative stress markers and in vitro responses of PA. RESULTS: Postnatal arterial partial pressure of oxygen and pH were higher and the oxygenation index and arterial partial pressure of carbon dioxide lower in betamethasone treated lambs. PA pressure was lower and systemic pressure higher in betamethasone lambs. Betamethasone decreased the oxidative stress markers and increased endothelial nitric oxide synthase expression in ventilated PPHN lungs. CONCLUSION: Antenatal betamethasone decreases oxidative stress and improves postnatal transition in late preterm lambs with PPHN. This study suggests a potential benefit for antenatal betamethasone in late preterm births.