Rape isn't a justifiable excuse to have an abortion.
Pregnancy in the event of rape is not relevant to the case for abortion on demand...To argue for abortion on demand from the hard cases of rape and incest is like trying to argue for the elimination of traffic laws from the fact that one might have to violate some of them in rare circumstances, such as when one's spouse or child needs to be rushed to the hospital. Proving an exception does not establish a general rule.
The unborn entity is not an aggressor when its presence does not endanger its mother's life (as in the case of a tubal pregnancy). It is the rapist who is the aggressor. The unborn entity is just as much an innocent victim as its mother. Hence, abortion cannot be justified on the basis that the unborn is an aggressor.
This argument begs the question by assuming that the unborn is not fully human. For if the unborn is fully human, then we must weigh the relieving of the woman's mental suffering against the right-to-life of an innocent human being. And homicide of another is never justified to relieve one of emotional distress.