Effect of corticosteroids on brain growth in fetal sheep

Objective: To compare the effects of single and repeated courses of cortico steroids on brain growth in fetal sheep. Methods: Pregnant sheep were given intramuscular betamethasone (0.5 mg/kg) at 105 days' gestation followed at 111, 118, and 124 days by equivalent vol umes of sterile normal saline (n = 12) or betamethasone (n = 12). Controls received equivalent volumes of sterile normal saline at all four intervals (n = 12). Lambs were delivered at 125 (preterm) or 145 (term) days. After p erfusion, we measured weights (grams) for whole brain, cerebrum, cerebellum and brain stem, volumes (milliliters) for whole brain and cerebrum, and ma ximum cerebral anterior-posterior length, width, and depth (centimeters). Results: In the single-injection group at preterm, there were no significan t differences (P =.070) in whole-brain weight between the corticosteroid-tr eated animals (38.0 +/- 1.81 g) and controls (42.5 +/- 1.65 g). Cerebral le ngth and depth were significantly reduced in the corticosteroid group (P < .05); other measures were not significantly different. At term, whole-brain weight was significantly lower (47.5 +/- 1.70 g; P = .022) compared with c ontrols (53.4 +/- 1.73 g). All other measures were significantly reduced (P < .05) except cerebral and brain-stem weights and cerebral length. In the group that received repeated injections at preterm, whole-brain weight was significantly reduced (35.5 +/- 1.65 g; P = .005) compared with controls (4 2.5 +/- 1.65 g). All other measures were significantly reduced (P < .05) ex cept cerebellar and brain-stem weights. At term, whole-brain weight was als o significantly reduced (42.4 +/- 1.52 g; P =.001) compared with controls ( 53.4 +/- 1.73 g) as were all other measures (P < .05). Conclusion: Administration of single and repeated courses of corticosteroid s to pregnant sheep retarded fetal braingrowth. (C) 1999 by The American Co llege of Obstetricians and Cyneeologists.