A nun is "automatically excommunicated" (and reassigned) because she was part of a medical ethics committee that concluded that a woman had to have an abortion or risk her own death. I always understood the life of the mother to be a reasonable excuse for such a thing, but apparently not:
"I am gravely concerned by the fact that an abortion was performed several months ago in a Catholic hospital in this diocese," Bishop Thomas J. Olmsted said in a statement sent to The Arizona Republic. "I am further concerned by the hospital's statement that the termination of a human life was necessary to treat the mother's underlying medical condition. An unborn child is not a disease. While medical professionals should certainly try to save a pregnant mother's life, the means by which they do it can never be by directly killing her unborn child. The end does not justify the means."
Olmsted added that if a Catholic "formally cooperates" in an abortion, he or she is automatically excommunicated.