Challenges in Prenatal Treatment with Dexamethasone.

Classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency causes elevated androgen levels, which can lead to virilization of female external genitalia. Prenatal dexamethasone treatment has been shown to be effective in preventing virilization of external genitalia when started prior to 7-9 weeks of gestation in females with classic CAH. However, CAH cannot be diagnosed prenatally until the end of the first trimester.