Why do women give birth?
Thats how god wanted it to be. Alternate answer: Because women have the reproductive system to do so. If men had the reproductive system of women and vice versa then women would be fertilizing men and men would have the children. Currently human reproductive-ness is not at all at any threat, just look at the worlds 6.7 billion people. With women producing the children we have lasted for many generations, not to mention the ones to come.