Cardiovascular responses to maternal betamethasone administration in the intrauterine growth-restricted ovine fetus.

OBJECTIVE: The objective was to characterize the effect of glucocorticoid treatment on fetal organ blood flow and regional cerebral blood flow in normally grown fetuses and fetuses with intrauterine fetal growth restriction (IUGR). STUDY DESIGN: Studies were undertaken in both control and IUGR fetal sheep; growth restriction was induced by ligation of 1 umbilical artery. Fetuses received colored microspheres for organ blood flow calculations before and after 2 maternal betamethasone injections (BM1 and BM2). RESULTS: Following BM1, cardiac output was significantly decreased in the control fetuses and blood flow to the heart and placenta was unchanged, whereas total cerebral blood flow was significantly decreased (P<.001), consistent with cerebral vasoconstriction. In the fetuses with IUGR, the cardiac output was significantly increased at +33 hours relative to BM1, and blood flow was increased in all organs; notably, there was a 2-fold increase in cerebral blood flow (P=.03). CONCLUSION: The cardiovascular response of the fetus with IUGR to glucocorticoids is profoundly different from the control fetuses, which may induce both short- and long-term injury.