WARNING OPINION INCOMING:
Abortion on demand ("I don't wanna be pregnant!") : Bad
Abortion because baby is "inferior" ("I don't wanna have to care for this baby who may only live two days") : Bad, I believe the baby should be given a chance to live, who knows, tests may have been performed incorrectly, or the damage not as severe as originally thought. If the abortion is because the parents don't want to have to raise a retarded child or a disabled one, that is pure selfishness on the part of the parents.
Abortion because mother would die otherwise ("I really want this baby, but if I have it, I will die and they baby may too") : *shrug* Depends on the situation I'd say. And this is rather rare in America.