To be blunt, a woman chooses to let a man stick his penis in her. That's where the choice about your own body comes in, and that's where it stops. Having an abortion isn't about what you do to your body, it's about the fact that you are ending a life that only exists because of your actions. Being pro-choice is just another way of not taking responsibility for what you do.
Now, I'll add that I think most of the people on this board who are against abortion, including myself, understand that cases of rape and incest are different. But if a woman goes out, has sex, and gets pregnant, it takes a lot of nerve for her to believe that she has the right to end that life for her own convenience.