Preterm newborn lamb renal and cardiovascular responses after fetal or maternal antenatal betamethasone.

The optimal dose, route of administration, and treatment-to-delivery interval necessary to induce beneficial extrapulmonary effects of glucocorticoids are not known. Pregnant ewes (127 days gestation) were randomized to receive maternal or fetal intramuscular injections of betamethasone (0.2 or 0.5 mg/kg body wt) or saline 24 h before cesarean delivery of their lambs. Three hours after delivery, low-dose maternal vs. control lamb mean arterial pressure [64 +/- 4 vs. 47 +/- 2 (SE) mmHg], glomerular filtration rate (1.7 +/- 0.2 vs. 0.7 +/- 0.1 ml.min-1.kg-1), and total renal sodium reabsorption (219 +/- 31 vs. 85 +/- 12 mueq.min-1.kg-1) were increased. Comparable increases were observed in the high-dose maternal and fetal groups without effects in the low-dose fetal group. This study provides the first quantitative data demonstrating that even short-term (24-h) antenatal betamethasone exposure alters preterm newborn cardiovascular and renal functions. These responses are route and dose dependent and are comparable to glucocorticoid-induced maturational effects after longer-term antenatal exposure.