Now, listen to me, this is the topic that I have seriously discussed many times in real life.
According to religions, abortion is a sin but life is farm from paradise.
1. If woman was raped and got pragnanted that way, it's definitely up to mother whether she wants to give a birth of do an abortion, no one can blame her because she was impregnated forcefully, without her will.
2. If Doctor tells couples that their child will have birth defect, then it's up to couple to decide whether they want to dedicate their life to that kid or do an abortion. Personally, I think that no one can blame mother for abortion in this case because child with birth defect usually makes life pure hell for parents and child also suffers from defect, some of them include pain, disabilities and etc.
3. If mother got pregnant accidently via one night stand and she doesn't want baby, then abortion is probably okay, probably, because child will suffer from growing up without loving parents and most likely she will be abused by a mother or stepfather. But this part is very debatable and I don't have fixed opinion about that. There are cases when mother doesn't want baby but grandparents take it as their responsibility to grow them, so, it's very debatable.
You just said my mind. Why bring a child into the world to suffer when you know you are not capable financially, morally and otherwise to raise a child? In as much as we know that most people abort their babies due to some selfish reasons, abortion cannot be wrong in all cases. Sometimes it is necessary to abort when the life of the mother is at stake.
In some countries where abortion is illegal, people tend to drink all form of concoctions or visit quacks who know little or nothing about the abortion process. This can result in complications for the woman or even death. Most times, if the foetus is not terminated successfully, it can can lead to some defects in the baby if the child is finally born.
In my view, abortion should be legalised for special cases like you listed above. You don't force a rape victim to keep a child simply because abortion is a sin. Having a child should be a matter of personal decision. And consenting adults should as much as possible protect themselves from unwanted pregnancy. This will save you the stress of going through the abortion process.