I didn't always feel this way. Anna Clark wrote a fascinating post at RH Reality Check about her evolution from being "pro-life" to being pro-choice. Amanda Marcotte also has an interesting debate on this topic happening at Pandagon. I made the following comment;
Both this post, and the one at RH Reality Check were really interesting. I went through a similar evolution in my opinions on abortion. Although now I would identify totally as pro-choice, there was a time when, although I never described myself as ‘pro-life’, I felt uncomfortable with the idea of abortion being used unless it was in the case of rape or for medical reasons. I don’t really know what changed. I suppose I grew up and had sex, and realised that life is not as black-and-white as I had previously thought. When I look back, I can’t believe that I ever thought it was just or fair to pit a fully-formed adult woman with an independent existence, thoughts and feelings, with a fetus.I suppose I wanted to expand on this point a little bit. In some senses, before I became sexually active, and was therefore forced to accept that an unwanted pregnancy was a risk for me, I was intellectually lazy about the whole issue. It is easier in many ways to believe that you are not one of the women who might have to have an abortion at some point in your life. You can feel morally superior to the women who do not live in the little bubble that you do. What I realised as I got older though, is that there is no particular type of woman who has an abortion. There is no particular reason why women have abortions, their reasons are as diverse as they are. And whilst I might never become a woman who has had an abortion, that doesn't mean that I shouldn't care about the rights, and the dignity, of women who have had to make that choice. After all, they are no different to me.
Just to add on a slightly different topic, someone in comments asked how pro-choicers should respond to the question, "why is it a baby when it is a planned pregnancy, and a fetus when it is unplanned?" Amanda Marcotte answered the question very well, by pointing out that we trust women to define their own experiences, so, for a woman who has being trying to get pregnant, she of course looks forward to the birth of her baby, and thus refers to it as such. In contrast, a woman who is faced with an unwanted pregnancy does not have that same happy anticipation of the birth. For her, it is only a fetus, and that it valid too. I would just like to add to the examples of self-definition that Amanda used. I think that a very good response to this question would simply be, "why is it 'sex' when you have consented, and 'rape' when you haven't?" Because people have different experiences, and so define those experiences differently.