I slept on my stomach until I was physically unable to and my daughter was fine. They say to sleep in different positions since it can help with circulation and breathing but my doctor said it shouldn't affect the baby.
Your fine until you hit about 20 weeks, then they say to sleep on your side (either side) if you can.
Alot of women still sleep on they're back or tummy until they just get too da*n uncomfortable. Personally I cant even sleep on my back and I'm only 21 1/2weeks pregnant. it's like I can't really breathe well. My bb's and tummy weigh me down.