I'm well educated, read lots of birthing books while pregnant, & gave birth for the first (and only ) time at 42 and didn't know that. And FWIW. I also gave birth very quickly, and had a drug-free, natural childbirth outside the hospital, attended to by just a midwife. I never felt the need to scream. In retrospect only did I realize I must have blacked out for the few moments when my DS actually emerged. If I had been alone, in a bathroom, I would have had no way of knowing what happened in those seconds, and given the "trauma" of birthing, little way of knowing what happened in the next few moments either.