Effects of three courses of maternally administered dexamethasone at 0.7, 0.75, and 0.8 of gestation on prenatal and postnatal growth in sheep.

OBJECTIVES: To evaluate the effects of repeated low doses of maternally administered dexamethasone (DM) on growth in sheep during fetal life and the first 2 years of postnatal life.

METHODS: Ewes received 3 courses of DM (1 course: four 2-mg intramuscular injections at 12-hour intervals) or saline beginning at 103, 110, and 117 days of gestation (dGA). At 119 dGA, fetal BW and organ weight were recorded. Total placentome number, weight, and morphologic distributions were recorded. Placentome glucocorticoid receptor expression was determined by immunocytochemistry. Newborn BW and organ weight were recorded within 12 hours of birth. Duration of gestation was recorded. Measurements were collected on body weight (BW), biparietal diameter (BPD), crown-to-rump length, thoracic girth circumference, abdominal girth circumference, and radial bone length for 2 months. Maternal estradiol and progesterone levels were measured daily from 135 dGA.

RESULTS: At 119 dGA, DM significantly decreased BW. Placentome glucocorticoid receptor expression increased after DM exposure. DM did not significantly decrease BW at birth but did prolong gestation length. DM decreased maternal estradiol before lambing. DM decreased newborn brain weight and BPD. After 2 weeks of age, no effect of DM on postnatal growth could be found.

CONCLUSIONS: This study shows that repeated maternal DM treatment at doses threefold lower than what women in preterm labor receive results in decreased fetal BW, prolonged gestation length, decreased newborn brain weight, and BPD.