Effect of Antenatal Steroids on Haemodynamics in the Normally Grown and Growth Restricted Fetus

The administration of antenatal glucocorticoids to women in preterm labour confers clear and significant benefits on perinatal outcomes, decreasing the incidence of respiratory distress syndrome and intraventricular hemorrhage in preterm babies, thereby reducing rates of mortality and morbidity. However, there is an evolving body of research addressing the non-pulmonary consequences of antenatal glucocorticoid administration, particularly in the growth restricted fetus. In particular, synthetic glucocorticoids, such as betamethasone and dexamethasone, are strong modulators of vascular structure and function such that antenatal glucocorticoids may have profound and lasting effects on fetal/neonatal cardiovasculature. This review examines the clinical and experimental literature on the benefits and risks of antenatal glucocorticoids in the well-grown preterm infant and in infants affected by intrauterine growth restriction (IUGR), highlighting the significant lack of specific information on the effects of antenatal glucocorticoids in IUGR infants. This is important because IUGR is associated with preterm birth and so the IUGR fetus is likely to be exposed to antenatal glucocorticoids. Recent experimental studies have shown that the fetal hemodynamic actions of exogenous glucocorticoids are profoundly different in IUGR fetus compared with the well-grown fetus with possible adverse implications for the development of the immature brain. Such observations merit caution clinically and further investigation.