I don't want to hear griping from the moms telling me how wrong they think I am for this..... My daughter was about 2 weeks old & she started sleeping on her tummy. Just 2 weeks. There are pros and cons to back sleeping, tummy sleeping and the new thing is side sleeping. Doctors and experts have gone back & forth on this for ages. I'm sure moms will send you links & stuff with safety this and SIDS that.... My daughter is now over 3 years old and perfectly fine. In fact, there were a few times she spit up in the night & rather than choking on it, she just spit it out in the crib. Yucky rub your face in but better out than in! :)