It seems there are two questions here.
The first is, when does the new life become a human person? I haven't seen any definitive answers of exactly when from those who hold the opinion that it is not. We would say that at conception, it is a human person. If allowed to grow, it will become a born human child (in most instances) and if nurtured, it will grow into an adult human. It's just a matter of stage. But it certainly isn't any kind of life other than human, and it clearly is alive, able to grow and move, and if female it already has the eggs that can become the next generation while still in the womb.
I realize that some consider "human person" or "human life" to have some other line in order to be true - I just haven't heard in this thread of when that is.
The second question is - is that life important/more important than the mother's. That's why I answered that question in my first post or two in this thread. It always come up. Our value (Orthodox Christians) is to preserve life. If the only way the mother can survive is to bring the child into the world, even prematurely, she can make that decision. If we had the medical ability to save the child, we would still attempt to do so. There is no sin in any of this. (If the mother chooses to risk her life in order to carry the child, as some women do who refuse cancer treatment if diagnosed during pregnancy, that is their right to decide too. No one can force such decisions on another person.)
But abortion is very rarely about saving the life of a mother who will die of it is not performed. A tubal pregnancy, perhaps, when both will die if not treated, and the baby with our current medical ability has no chance at all.
It always dissolves into talking about other issues and muddying the water. This has been discussed since the days of the Apostles - babies were being killed in utero and exposed to die after birth. In every case, Christianity condemned it as murder. (It was never done to save the mother's life at that time.) Our reasons now (except to save the mother) go against the teaching of Christianity. Period.
