No one is obligated to do anything. Whether I have an abortion or not, or I kill someone unknown, hardly anyone will truly be affected. Childbirth is not relevant to us either. In tribes and small villages; anything trying to keep something alive, births might be more relevant. And honestly, we should not care even then. If everyone just stops giving birth, then that is an issue, but natural drives to have children and raise them will always prevent all of that.
It is not a woman's sole purpose to have children. It is also not a man's obligation to impregnate a woman, and as we have seen in our lifetimes, humans are good for much more than just procreating. Some women (and men) choose to take care of children that are not their own, or contribute to the world in another way. Not to mention, some women are physically unable to bear children. Shall I even mention body autonomy?