I still sleep on my belly. I know someone who at 20 weeks is still sleeping on her belly. Generally, sleep how ever you want as long as it's comfortable for you. I think around 20 weeks your suppose to be careful of sleeping on your back because the weight of the fetus *can* restrict blood flow, but I've heard people here on MDC say that's a myth.
Laying on your back after, say 20-24 weeks, would put pressure on your Vena Cava I think it is. I don't think it's a myth for some people. And you do get better flow on your left side.<br><br>
Sleeping on your belly seems to be a comfort issue. I would assume you would stop being able to before it got dangerous (if it gets dangerous).<br><br>
But what do I know?! I wake up sometimes on my stomach, but much less frequently now. The weird thing for me is waking up in the exact position I go to sleep in because I am waking every 45 minutes to 1 hour usually to pee all night and when I nap in the daytime. SOMETIMES closer to two hours, but that's unusual.