If sex were natural, then like the animals, we would know how to do it without being taught. Natural things don't require anything being taught. It's not natural for people to speak and just because they do doesn't mean it's natural. Talking is a condition, just like intercourse.

Maybe I should have been clear about what I mean. In the examples you listed, the woman does not want to be pregnant. The only difference between is the last one and the other examples is that the man wants the woman to have to have the baby. What you are doing giving the man the final authority (not so different from the Pope in that regard), when it is the woman's body that is at the issue. If a fetus is just potenial, like an idea, then the woman has the right to do anything with the idea she is given no matter what the man wants. Since men always have the "me stronger, me more powerful" card, I hardly see why pregnancy can't be the domain where women have a greater deal of control.