A hard question because each is different. Some may, some may not.

How my guides explain it to me is this. A soul can choose to enter the body at any time in conception. They may choose to go through this death for reasons solely their own or for the sake of the parents (lessons). Some do not enter the body at all.

So in a nutshell, there is no answer that is absolute. As for what happens to the soul, it returns to the Other Side, just as you and I will. Maybe it will come back to the same parents at a different time or not at all.