The most important thing in life, from the biological point of view is to be able to generate offspring, transmit your genes, have children, etc.
The human body is wise and knows how to distribute the greatest essential requirements for our heir. But this implies that also in some occasions.
From the general and scientific point of view, the doctor should do everything possible to save the baby. The whole organism that managed to reproduce is already biologically successful.
From my point of view, and emotional, I would prefer to safeguard the mother .. although there is a risk that I can not have more babies.
From the ethical point of view, the doctor will keep a place for the present.