I haven't read it, but I often wake up from having been sleeping on my back and at almost 7 1/2mths pg, I feel fine after doing so. No dizzyness for me. I also layed on my back alot when pg with my other bubs, and never had issues. I think it all just depends on your own individual anatomy! The risk is supposed to be that you can put a fair bit of pressure on a major vein or artery or something and it can cause dizzyness and fainting. I suppose if baby isn't in a position to be laying on the vein in question, then you won't get the symptoms!!