In the case of rape or incest; the baby has done no wrong so why murder it.
In the case of the motherâ€™s health being threatened by her pregnancy:
"When the life of the mother is truly threatened by her pregnancy, if both lives cannot simultaneously be saved, then saving the motherâ€™s life must be the primary aim. If through our careful treatment of the motherâ€™s illness the pre-born patient inadvertently dies or is injured, this is tragic and, if unintentional, is not unethical and is consistent with the pro-life ethic. But the intentional killing of an unborn baby by abortion is never necessary."