It doesn't really come up very often at all in the real world. Many things are wrong with the idea of this. First and foremost, a law against procured, purposeful abortion wouldn't prevent a doctor from saving a woman's life. It wouldn't have an effect on the less than 1% of abortions which occur for this reason. The ethical thing would be for abortion to be illegal, and for doctors to genuinely make every effort to save both mother and child. If the baby dies as a secondary effect of saving the mother, without any action taken to specifically kill the woman's child, then no unethical killing has taken place. "Abortion" in the process of saving a mothers life is not abortion. It is an unintended effect, and a failure in the saving of both the mother and the baby.