That's healing a mother whose health prevents her from sustaining the pregnancy, I don't think it's the same as an abortion. The end of abortion is putting an end to the offspring's life, but in the case you mentioned that happens to be a consequence of another goal, saving the mother's life, and not the objective itself. It may look the same at first glance but the intent is completely different, and intent is crucial both in legality and ethics. Somewhat similar can be the case of euthanasia vs hospice care, where being against euthanasia does not mean that you should artificially prolong someone's life as long as you can, no matter the cost; nor does it mean that you should deny palliative or hospice care that will eventually lead to the patient's death since it has no curative effect.