Antenatal glucocorticoids and the developing brain: mechanisms of action.

Glucocorticoids are critical for normal brain development. There is no doubt that prenatal treatment with synthetic glucocorticoid affords great benefit to the preterm infant. However, animal studies, now carried out in many species, indicate that there may be some long-term physiological costs of early exposure to excess glucocorticoid, and that these appear sex-dependent. Further, the effects may not become apparent until later life. Given the dynamics of corticosteroid receptor systems in late gestation, it is likely that there are critical windows of development when specific regions of the brain are more sensitive to the influence of synthetic glucocorticoid. Once such windows have been identified it will be possible to target prenatal treatments, so as to maximize benefit and reduce risk of long-term effects. Notwithstanding, the data reviewed below indicate that caution should be exercised in the use of multiple course glucocorticoid therapy during pregnancy.