Effects of antenatal glucocorticoids on pulmonary vascular reactivity in the ovine fetus

Objectives: Although mechanisms of glucocorticoids-induced parenchymal lung maturation have been largely studied, little is known about the pulmonary vascular effects of antenatal glucocorticoids (GCs). We therefore hypothesized that antenatal GCs may alter the hemodynamic response to vasodilatory agents in the fetal lung. Study Design: We tested the hemodynamic response to acetylcholine, increased PaO2, and norepinephrine infusion before and after maternal GC administration in chronically prepared, late-gestation fetal lambs (135-137 days of gestational age, term = 147 days). Results: We found that antenatal GCs (1) do not change the basal pulmonary vascular tone and (2) do not alter the vasodilatory response to acetylcholine and increased PaO2 but enhanced the norepinephrine-mediated pulmonary vasodilation. Conclusion: Our results indicate that antenatal GCs alter the pulmonary vascular reactivity to catecholamines. We speculate that the benefits of antenatal GCs on the cardiovascular adaptation at birth may be related to potentiation of catecholamines vascular effects. (Am J Obstet Gynecol 2003;189:208-15.)