I've skipped to many lessons on biology xd
I tough that visible genitalia wouldn't appear untill the first 3 orso months of pregnancy?
Visible genitalia are being created according to the combination of X and Y chromosomes. The only instance of disfigurment may appear when the chromosomes are formed in an erronous way, casuing hermaphroditism, among others... but I digress. Point being, when the first helix is created, there ain't no turning back anymore - it's either XX or XY (...or the previously mentioned erronous combinations).