In most conditions in which the mother is in grave condition because of an unborn child, the child has already passed away. Removing an incomplete miscarriage (no heart beat is detected) isn’t the same as an abortion.
Other situations, such as pre-eclampsia, where the mother’s life is in grave danger, doesn’t tend to happen until the third trimester, in which case labor can be induced and the baby born early.
What condition did you have in mind in which the mother is at risk of dying and the baby is still alive in the womb? I would be able to answer your question better if I know this information.
Abortion is a grave sin, but God is merciful. This does not mean you can get an abortion and God will forgive you. Our salvation isn’t guaranteed, only our path to salvation is. What you do in life gets you there, following the Lord’s teaching is how. So someone having an abortion doesn’t mean they are doomed to hell so to say if they truly repent, are truly remorseful, accept complete responsibility for there action, and refrain from doing it again. If you do these things then there is a chance God will forgive you. This does NOT mean you can get an abortion and assume repenting will guarantee you will go to Heaven. Believing in Jesus and upholding the sacraments does NOT mean you can go out and kill someone and all is forgiven, salvation doesn’t work that way.
That being said, the Catholic church offers support programs for those who have committed the sin of abortion and are in need of help. More about these services can be found here, and an open letter to women who are struggling after abortion can be found here.
And no, you cannot go out and bomb an abortion clinic or other vigilante justice.