Prenatal virilization of a genetically female fetus can occur when an excessive amount of androgen is produced by the fetal adrenal glands or is present in maternal blood. In the severest form of congenital adrenal hyperplasia, complete masculinization of a genetically female fetus results in an apparently normal male anatomy with no palpable testes. More often, the virilization is partial and the genitalia are ambiguous.
It can also be associated with progestin-induced virilisation.