I've read everywhere and been told by Drs that once I hit a certain mile marker in my pregnancy that you need to start sleeping on your left side.  I started right away trying to sleep train myself and just had a little pillow prop me up a little bit. Well, this week I found out the hard and painful way that I have kidney stones & after 2 ER visits consulted with an MD that it's even more important for me to sleep on my left side so there is less pressure on my kidneys.