The Hypothalamic-Pituitary-Adrenal Axis and the Fetus

Glucocorticoids (GCs), cortisol in humans, influence multiple essential maturational events during gestation. In the human fetus, fetal hypothalamic-pituitary-adrenal (HPA) axis function, fetal adrenal steroidogenesis, placental 11β- hydroxysteroid dehydrogenase type 2 activity, maternal cortisol concentrations, and environmental factors impact fetal cortisol exposure. The beneficial effects of synthetic glucocorticoids (sGCs), such as dexamethasone and betamethasone, on fetal lung maturation have significantly shifted the management of preterm labor and threatened preterm birth. Accumulating evidence suggests that exposure to sGCs in utero at critical developmental stages can alter the function of organ systems and that these effects may have sequelae that extend into adult life. Maternal stress and environmental influences may also impact fetal GC exposure. This article explores the vulnerability of the fetal HPA axis to endogenous GCs and exogenous sGCs.