I never understood the rape/incest exception, because
(1) you don't allow the child to get aborted because of something the father did (unless you don't oppose abortion in the first place, of course), and
(2) there's always the possibility of abuse (which is what Link is talking about). If a woman is going to kill her baby (already a despicable thing to do), what's to stop her from lying about rape? Anyone can say I got raped and no one will bother to check (certainly not the abortion clinic!)
This post is why men should not make decisions on women's bodies.