By her eighth month of pregnancy, Rebecca Sloan, a 35-year-old biologist living in Mountain View, Calif., had read the what-to-expect books, taken the childbirth classes, joined the mommy chat rooms and still had no idea what she was in for. So, like countless expectant mothers before her, Ms. Sloan typed "childbirth" into YouTube's search engine. Up popped thousands of videos, showing everything from women giving birth under hypnosis, to Caesarean sections, to births in bathtubs.
