The development of the female external genitalia is promoted by the presence of estrogen and other hormones within the maternal system. The phallus described earlier continues to grow to become the clitoris. Meanwhile, the urogenital folds are developing into the labia minora. Their development is similar to that in the male. They grow up along side the phallus except that in the female, they fuse only at the most posterior aspect to form the frenulum.
The labioscrotal folds continue to grow as well, fusing at their most posterior and anterior portions to form labial commissures. The portions of the labioscrotal folds which do not fuse form the labia majora.
In the female, the anus and urogenital orifices (urethra and vagina) open into the same cavity, the vestibule of the vagina.
For the sake of comparison, it should be noted that the vestibule is homologous to the male penile urethra and the labia majora to the scrotum
If there are excessive androgens present in the fetus during development of the external genitalia, varying degrees of masculization of the external genitalia may occur. This is known as adrenocortical hyperplasia
