I heard from a reliable source that pg women should not do any exercises on her back because the weight of the uterus may press on the large blood vessel that brings a major amount of blood from the lower extremities back to the heart inferior vena cava. Now I'm freaking out because when I sleep I always start out on my side but usually end up on my back. I'm thinking that if its bad to be on your back when you workout then it's bad to be on your back when you sleep. Has anyone else run into this problem? Any solutions?