Pseudohermaphroditism in a female child is most commonly due to -
Classic 21 α hydroxylase deficiency is the most common cause of Ambiguous genitalia in a new born.

Pseudo hermaphroditism

A congenital abnormality of the external genitalia and of the body in which one possesses sex glands of one sex but genitals of the opposite sex.
21 α hydroxylase deficiency
17 α hydroxylase deficiency
11 β hydroxylase deficiency
3 β Hydroxysteroid dehydrogenase deficiency