Oh and if you do have to lay on your back, which I think is ok to give your body a break honestly, then just make sure you are "belly breathing". When you look down you should see your belly moving, not your chest moving up and down. This will help to circulate oxygen to the baby. I wake up in the middle of the night on my back sometimes, which my doctor said obviously you can't help, so I don't think relaxing on your back for a few would hurt. Just don't stay there for hours.