Around our house, we assume the spirit in a baby is a functioning, living, adult spirit from conception. This affects our treatment of our babies, both before and after birth, as we try our best to be nice to them--even to the unborn.
This article, which is ten years old, was very interesting on that point. Apparently scientists have been saying for some time that if you try to force your child to develop better or faster, you may actually be harming them.
It's a very pop-sci article, without real evidence from the studies, but fun to read nonetheless.