How does Buddhism define abortion?
In Buddhism, life starts at the moment of conception. So abortion breaks the 1st precept and causes bad Karma no matter how you try to justify it. Even if the husband's intention is to save the wife(mother), it still causes bad Karma. To give you an analogy, let's say a bear captured your wife and is about to kill her. Say you have a gun with you. You can shoot the bear and save your wife, but it still breaks the 1st precept and causes bad Karma.