Single and repetitive maternal glucocorticoid exposures reduce fetal growth in sheep

OBJECTIVE: We evaluated the effects of single or three repeated doses of maternal betamethasone on fetal growth at preterm and term delivery in sheep. STUDY DESIGN: Pregnant ewes were randomly assigned to receive one dose of 0.5 mg/kg betamethasone at 104 days' gestational age; three doses of betamethasone at 104, 111, and 118 days' gestational age; or saline for controls. Lambs were delivered at 125 days' (preterm) or at 145 days' (term) gestational age for assessments of fetal growth. RESULTS: The single betamethasone exposure at 104 days' gestational age caused symmetric growth retardation of 11% at 125 days' gestational age and 14% at term. The three-dose exposures decreased body weights by 25% in preterm lambs and by 19% at term. Organ protein and deoxyribonucleic acid per kilogram of body weight were selectively decreased in preterm lambs. At term the decreases in organ weight, protein, and deoxyribonucleic acid were proportionate to the decreased birth weight. CONCLUSION: One or three doses of maternal glucocorticoids begun at an early gestational age caused symmetric growth retardation in lambs delivered prematurely, and the decreased fetal size persisted to term.