The "medical difficulties" that they would have caused involved the death of all 4 babies. With the mother having serious enough complications to require hospitalization at only 15 weeks of pregnancy, there was virtually no chance of all the babies surviving, a large chance that they would all die, and a certainty that any who survived would have serious mental and physical disabilities. It makes no sense to take a large risk of killing all the babies by trying to keep them growing inside a mother whose body couldn't handle this, and therefore couldn't provide adequate nutrition and oxygen to these way pre-viable fetuses, when they had the option of delivering 2 healthy babies instead.
My wife had to be hospitalized at 20 weeks and again at 24. My son made it fine. Pregnancies are often difficult, assuming the sky is falling every time there’s something wrong is being hysterical.