Prenatal yoga also helps prepare you for a natural delivery and can be quite informative about labour, pain, what to expect, etc (depending on teacher and classes).
I practised prenatal yoga throughout my first pregnancy and trained to teach prenatal yoga at the same time, and my 12-hour labour was completely natural, drug-free and manageable. I'm pregnant again and due in June. Pls. see: hershayoga.com if interested to take prenatal yoga classes