What should be done when during pregnancy the life of the mother is under threat and doctors recommend abortion?

From: Utkarsh Parekh

I have a dilemma, my sister in london is in her 3 trimester of pregnancy, her water has broken. part of the foetus membrane has also come out. She is under observation and undergoing complete bed rest.

Doctors have advised after check up to abort the child (MTP) they say that child growth will be abnormal. Keeping child would entail risk to life of mother & also the foetus, since they are unsure of its growth.