This a problem I find with it, too. Advocates of NFP will say that it is more effective than ABC in preventing pregnancy, and that it can be safely used by women who face dangerous pregnancies. While at the same time, it allows intercourse to remain ordered to procreation. If a woman is endangered by procreation, ordered to procreation is exactly what you don’t want.
What this means, to my sense, is that a woman who is endangered by pregnancy **and **who practices NFP **and **who gets pregnant has had herself endangered by God’s Will. I cannot accept the idea that God wills people to get sick and die.
When my neighbor got pregnant against her doctor’s advice, and she died as a result, was it God’s Will that she leave behind a husband and three young children, as well as lose the in-utero baby? It was, if anything, her free will that led to her death. She knew the risks and chose to take a chance. She lost. But that was not God’s Will.