This person is less than an animal. The children might cause medical difficulties, so let's pick two that we will execute. Never mind that playing God is not for humans. It's much easier to rationalize murder when you can claim some possible health risk or that humans are the highest level of consciousness.
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.