I'm sure it's just a matter of numbers before one would need to save the mother's life, but I could only imagine it would be extremely rare. They almost passed a bill back when Clinton was president to limit abortion (late term only if I recall correctly) and Clinton wanted to change the words "life of the mother" to "health of the mother". That could have been mental health. I recall it was quiet in the Senate waiting for the vote and it was either right before or after the veto override vote was cast, a baby started crying.