personally, i believe there is nothing wrong with infant deaths.
ofcourse id rather they all live to a ripe old age, but - like the rest of nature - we compete for resources, food, warmth, etc.
some deaths will occur, and indeed do with the young ones.
if the mature parents cannot support the infant for its first few years (id say 6 is the minimal age from which a human can survive alone) and they have a less than reasonable chance of surviving to help it grow, it, from a survivalist point of view, it makes sense to keep the "investment" made in the parents.
if they live on, they can sire other children.
that is cold and calculating, but what i believe to be correct.
however, ALL parents would (usually) DIE to save thier children.
that is what I would do if i had to choose.
so, again, personally i would never kill one of MY infants.
during the pregnancy the feotus is not human - in a reasoning, conscious manner.
i dont see a problem with ending it, in order to save the mother.
overall it depends on the reason for killing the infant.
if the reason is to save an older, more fertile person, that can sire more children later on, it is sad, but needed to ensure that the family-clan- survives.
if that infant is to be killed because there is no possible way it will survive to maturity, it is better to save the invested time and effort and put those into other children.
if it is just about killing infants so that you can have better lives, that is wrong.
if its killing so that YOUR children survive - you ha better guard your young ones. im coming after them!