Why you should sleep on your left side

A recent article  showed that sleeping on the back and right side predisposes to a higher incidence of sudden death of the foetus. Although further studies need to be done, it would be prudent to follow this rule especially if you are in your third trimestor. The incidence of stilbirth is not high and is less than 1: 10000. Very often it is attributed to a cord accident but in a large proportion no obvious cause is found. It may be that sleeping on the back and right could well be a cause. Pregnant women have always been told to sleep on the side and the reason is that there is a major vessel running parallel to the spine on the right and behind the womb. As the womb expands there will be increased pressure on this vessel. This blood vessel also supplies the foetus with oxygen and nutrition. The womb is naturally tilted to the right, thus it would make sense that sleeping on the right and back would increase the pressure on this vessel possibly reducing the oxygen to the foetus.
So always remember to sleep on the LEFT side!

http://www.medscape.com/viewarticle/744648?sssdmh=dm1.695983