When it is really and truly a definite choice of only one between the mother and the baby, the mother “wins”, especially if there are other children involved. That’s a miniscule fraction of one percentage, and is a totally different situation than the rest of them because of the fact that it has to do with saving lives. Save one or the other, the mother needs to take care of any other children she has, and may be able to have another baby.
But if it is a choice between killing the innocent baby or (something else that does not mean certain death for the mother), then murder is not an option. Saving the mother’s life is not murder in a case like the one described.
See a picture here of a baby at 20 weeks from conception, sucking his thumb:
http://www.medicinenet.com/fetal_development_pictures_slideshow/article.htm
http://www.babycenter.com/fetal-development-images-20-weeks
At eight weeks, it has a beating heart:_slideshow/article.htm
Abortion is a practice that involves the baby more than anybody else, including the mother.
http://www.medicinenet.com/fetal_development_pictures