It would be trajic to all indeed. The future mother and her family would have to face their options. One option should surely be adoption. Unless you simply prefer the death penalty for the unborn fetus. In cases like that, most of us in society would agree that at least three options should be made available. Most would probably opt for adoption.
And if a mother brings an infant into the world with birth defects that continue to make it wholly dependent on the mother, then the government should have to continue to have no voice in whether that mother continues to provide support for the newborn infant, or end it's life. Just a continuation of your logic.