Glucocorticoids in the fetus are either of maternal origin or syntheiszed from placental progesterone in the fetal adrenal cortex(which lacks zona reticularis). Glucocorticoids are essential for a lot of developmental events, but three of them are most important which goes as follows.
1. The production of surfactant by Type II alveolar epithelial cells after the eight month of life. That is why we administer betamethasone or dexamethasone to mothers at risk of preterm birth to reduce the risk of respiratory distress syndrome.
2. The development of a functional hypothalamo-pituitary axis; which is essential for development of reproductive cycle and modulation of myriad endocrine functions.
3. The induction of thymic involution. That is why we do prolonged corticosteroid therapy prior to complicated thymectomy and which also inhibits thymopoiesis albeit reversibly.