What determines the gender of a baby?

if the baby is in the right position a sonographer can usually tell what the sex is at your 22 week sonogram. they say if you carry the baby high it is a girl and if you carry a baby low it is a boy. that was how it was for me , but i wouldn't rely on it. with my son i carried really low and all out front and with my daughter i carried high and wide( she is the reason i now have love handles) also alot of women "just know". trust your instincts!!!!