Disorders of sexual differentiation, otherwise known as intersex disorders or ambiguous genitalia, are a broad spectrum of conditions that result in the baby’s genitalia being not well formed or having characteristics of both sexes.

This can result from chromosomal, gonadal, or genital abnormalities.  Females with ambiguous genitalia can have enlargement of the clitoris, abnormal appearing labia, and fusion of the vagina with the urethra (urogenital sinus).  Males with ambiguous genitalia can have a small penis, hypospadias, a small or abnormal appearing scrotum, and undescended testicles.

The most common cause of ambiguous genitalia is congenital adrenal hyperplasia, which occurs with an incidence of 1 in 15,000 live births. These children lack an enzyme in the adrenal gland that is necessary for processing corticosteroids, and as a result, accumulate steroid intermediates that cannot be processed by the defective enzyme.  In virilizing (masculinizing) forms of this disease, these intermediates lead to increase production of androgens (male hormone) during fetal development which can lead to masculinization of the genitalia.