Most common cause aof ambigious genitalia in a female child is
CONGENITAL ADRENAL HYPERPLASIA

Clinical presentation: Ambiguity of sex detected at birth are due to androgenital syndrome unless proved otherwise. Hirsutism and amenorrhea may be presenting features around puberty in milder form

Diagnosis at birth

An enlarged clitoris
Presence of penile urethra or hypospadius
Hyponatremia,hypakalemia and hypotension
Fusion of labia minora
Placenta steriod sulfatase deficiency
Fetal aromatase deficiency
Wnt4 mutation
Congenital adrenal hyperplasia