Single and multiple prenatal glucocorticoid exposures improve preterm newborn lamb cardiovascular and renal function similarly

OBJECTIVE: Renal and cardiovascular function improves in preterm newborn lambs after a single prenatal betamethasone treatment. We hypothesized that multiple betamethasone exposures would further improve renal and cardiovascular adaptation. STUDY DESIGN: Pregnant ewes were chosen randomly to receive saline solution, one dose of 0.5 mg/kg betamethasone at 104 days of gestation, or three doses of 0.5 mg/kg betamethasone at 104, 111, and 118 days of gestation. Lambs were delivered at 125 days of gestation (preterm) or 145 days of gestation (term). Renal and cardiovascular responses to phenylephrine were evaluated at 2 hours of age. RESULTS: The preterm single and multiple betamethasone-treated lambs comparably increased glomerular filtration rate, urinary flow and osmolar clearance, and sodium excretion in response to phenylephrine. Term responses were similar and not influenced by betamethasone exposure. CONCLUSION: Multiple courses of betamethasone do not further improve renal and cardiovascular responses from a single betamethasone dose. Renal and cardiovascular function at term is not affected by early prenatal betamethasone exposure.