Eclampsia would be a reason for ending a pregnancy. It's an extreme complication of pregnancy, that by definition, occurs after 20 weeks. A pregnant woman develops seizures and altered mental status (like being in a coma.) It's associated with severe hypertension (BPs 200+/120+,) generalized edema, and signs of kidney, liver, and other organ dysfunction. I saw a case early in my training which I never forgot. She was a teenager, and about 22 weeks into her 1st pregnancy--which are risk factors. When she wasn't having seizures, she was comatose. Her BP was sky high (systolics well over 200 as I recall.) Her kidneys were failing, and she was becoming massively swollen with fluid. There are medications which can help, but she was on max doses and not responding at all. The only definitive treatment is to end the pregnancy. Which means to induce labor or do a C-section ASAP. That's what had to be done in the case I saw. OK, strictly speaking, this isn't performing an abortion. But even with today's high-tech neonatal life support, a 22 week preemie's chance of survival is
0-10%. So it is terminating a pregnancy in a way that will very likely result in a dead baby. But it may be necessary to save the mom's life, or prevent a catastrophic cerebral hemorrhage or other permanent brain damage.
http://emedicine.medscape.com/article/253960-overview#a1