it's more needed later on. I could sleep on my back even tho I usually prefer my left side but the baby will position itself where it feels like a bowling ball is pulling away from your uterus when ur on ur back it'll suddenly be more comfortable in ur side.

I was that way until 31 weeks. I even slept on my belly sometimes because laying on my side would get old and I would need to reposition my self. but once you hit a certain time you can't sleep on your back because it cuts circulation of which makes you light headed and it also makes it a lot harder to breath. you'll find you don't really get much sleep after 30 or so weeks in between trying to get comfortable and all the poddy breaks.