There are rare casses where a mother's life is put in danger by her pregnancy, yes. Are we to then justify abortion for everyone else based on these rare cases? I may have to shoot someone out of self defense, but this doesn't make it OK to shoot any one for any other reason, does it?
My arguement against abortion is that we must preserve human life. All human life. When it comes down to a life or death situation I can see how the woman should be given a concession to terminate the pregnancy. Her life and the child's life are equally important. I think, though, that if we as a culture accepted the full personhood of the unborn, a lot more women than you might think would opt to risk their lives for their children. I know that I would.