Well, the life of an individual being certainly starts at conception, but of course the conceived foetus is at that point no more alive than a tree.

(Also, once again, you are merely claiming that murder is the most vile act we can commit against one another; I completely disagree.)

There doesn't seem to be a satisfcatory point post-conception but pre-birth at which we can say that the foetus is now alive. One point is viability -- i.e. the point at which it could survive outside the womb as an independent being -- but as time and technology march forward, the line of viability becomes earlier and earlier and indeed foggier and foggier.

The only point that is satisfactory, to me, is personhood. Personhood -- as opposed to being-a-human -- makes a being's life valuable, and the potential for personhood is why the killing of foetuses and babies is unideal (but not impermissible).