Estrogen receptors are present within the fetal brain, suggesting that estrogens may exert an influence on cerebral development. Loss of placentally derived estrogen in preterm birth may impair development.Baboons were delivered at 125 days of gestation (term approximately 185 days), randomly allocated to receive estradiol (n = 10) or placebo (n = 8), and ventilated for 14 days. Brains were assessed for developmental and neuropathological parameters.Body and brain weights were not different between groups, but the brain/body weight ratio was increased (P < .05) in estradiol-treated animals. There were no differences (P > .05) between groups in any neuropathological measure in either the forebrain or cerebellum. There were no intraventricular hemorrhages; 1 estradiol animal displayed ectactic vessels in the subarachnoid space.Brief postnatal estradiol administration to primates does not pose an increased risk of injury or impaired brain development.