Pseudo hermaphroditism in a female child is most commonly due to:

a. 21-hydroxylase deficiency(Ref: Nelson's 20/e p 2714-2723, Ghai 8/e p 526-527)Classic 21-hydroxylase deficiency is the most common cause of ambiguous genitalia in a female newborn. Virilization is usually apparent at birth in females, i.e. Pseudo hermaphroditism of a female child.