Can we be sure if a baby's going to die anyway? Can we ever use abortion as an escape?

There have been many times when a doctor has assumed that an unborn baby will not survive through birth and then asked the mother to end her pregnency, when the mother refuses to end her pregnency and it turns out, the baby is able to survive.

When can a mother or a doctor be sure a baby will not survive birth? Different events in history shows that doctors often make mistakes like these or manipulate their ideas to support their own theory. The Bible and other sources of history both show that it's possible for any sickness to be cured, although there's no garntee of it.