Some say yes, some say no. I prop myself up with all these pillows and still wind up on my back every night. If I wake, I figure I must be uncomfortable (and/or need to pee AGAIN!) so I go for side again but inevitably I still wake on my back in the morning. I'm 32+4 and bub's big & healthy& strong, so I figure im doing it all right!
The benefit of sleeping on ur sides especially the left is u get a better blood & oxygen flow 2 the baby. I'm the exact same way as BCD13. I begin every night on my left side prop myself with my body pillow and tons more pillows roll around to the rt & wake up on my back. I have read horror stories, but I'm 26weeks & my baby is fine. If ur going to lay on ur back try not 2 lay flat prop urself up.
I don't lay on my back because I get short of breath and it's way too much pressure on my stomach, makes me sicker than a dog.
I have always been a side sleeper, so I wake up on my back all the time and just roll up to my side again. If you can work out the specifics, put some pillows a short way behind you while you're on your side. This way you can still lay back and relax, but won't have troubles back sleepers have while pregnant. It's kind of like reclining in your bed.
At both my birth classes and prenatal yoga they emphasize NOT sleeping on your back. Apparently even if *you* feel comfortable it cuts off oxygen & nutrients to baby. I wall myself in between pillows so I don't roll over. Lol.
Also, I heard that reclining on your back does something to the baby's position... Basically baby prefers the breech position when you recline. This part I haven't done research on, but the back sleeping I have. :)