The Bible doesn't teach there is such a thing. A person begins when he or she is conceived. Your question makes it sound as if there is a reservoir of pre-existing, unborn souls waiting for a body to inhabit. That is not a biblical teaching.

Secondly, limbo is not a biblical teaching. It's a Catholic doctrine that comes from the pen of a pope, and it's not in the Bible. Protestants don't believe in limbo because it's not in the Bible.

If everyone stopped having children tomorrow, where would all the souls end up? Limbo?