For LDS, what are the references in our literature about being litteraly born as spirit children.?

Also does the church still hold that standing? It would be pretty amazing to think that our heavenly mother was pregnant and gave birth to the billions of people that have ever lived on this Earth plus the spirits that populated innumerable Earths like our own. I wonder who performed all those deliveries? I guess since she gave birth to spirits though, they would come out a lot easier though, like water or something. Do we actually beleive this still, I hear about it at church and a number of promormon sites on the internet. where does this idea come from?