Betamethasone may damage brain of growth-restricted fetus

Intrauterine growth-restricted fetuses given antenatal glucocorticoids to promote maturation of the lungs may be at increased risk of brain damage, according to the results of a study in sheep published in the March issue of Endocrinology.

Euan M. Wallace, MD, of Monash University in Victoria, Australia, and colleagues conducted a study in sheep pregnant with twins. The size of one of the fetuses was restricted by ligation of the fetus's umbilical artery while the other twin was used as a control. Five of the ewes received betamethasone while four received saline on two consecutive days after surgery.

Carotid blood flow in the control fetuses decreased 3.5 hours after the first dose of betamethasone was administered, before returning to baseline at the 5.5-hour mark. However, in restricted-growth fetuses, carotid flow declined by a similar amount as in the control fetuses, but shot 25% over baseline, peaking at 11 hours.

Miller SL, Chai M, Loose J, et al. The effects of maternal betamethasone administration on the intrauterine growth-restricted fetus. Endocrinology. 2007;148:1288-1295.