Abortion is murder, but murder can be justified.
It's always on a case by case basis and it should be mainly up to the mother and the doctor.
The mother's health needs to come first, so if a fetus is threatening mother's life and there is no other safe option then abortion is absolutely legitimate.
Another case would be severe genetic disabilities as that individual is nonviable anyway (yes, eugenics) and the mother shouldn't be forced to take care of them.
Another case is rape. This one is difficult as not wanting the child to be a reminder of the traumatic experience is understandable however children shouldn't be punished for crimes of their parents. Adoption is probably better tbh.
Than there is "I'm not ready" and that's not a justification, that's an excuse. Nobody is ever ready to be a parent.