I remember reading "The Good Earth" by Pearl S. Buck in high school, in which the mother euthanizes her own child in order to survive.
It's interesting to see what Buck herself had to say:
“… I fear the power of choice over life or death at human hands. I see no human being whom I could ever trust with such power – not myself, not any other. Human wisdom, human integrity are not great enough. Since the fetus is a creature already alive and in the process of development, to kill it is to choose death over life. At what point shall we allow this choice? For me the answer is – at no point, once life has begun. At no point, I repeat, either as life begins or as life ends, for we who are human beings cannot, for our own safety, be allowed to choose death, life being all we know.”
[Italics added]