Sleeping on your back while pregnant can create pressure on a major vein called the inferior vena cava. This vein returns blood from the lower body to your heart. This may lead to lightheadedness and/or numbness. In addition this may cause pressure on your back and intestines, leading to discomfort.
Sleeping on your stomach is not recommended because it can cause pressure on the fetus.
Most physicians recommend that a woman sleep on her left side while pregnant. this allows for the maximum blood flow to the baby, and it will also improve kidney function for the mother. The improved kidney flow will help to reduce swelling. Because your liver is on the right side of your body, sleeping on your left will keep the pressure off your liver.
Early in pregnancy, you should attempt to get into the habit of side sleeping. Typically the most comfortable position is with your knees bent. You may wish to place a pillow between your knees to sleep more comfortably.
The best sleeping position for a pregnant woman is on her side, especially the left side, because it allows for maximum blood flow to the fetus and improves kidney function in the mother. Improved kidney flow helps to reduce any swelling. Placing a pillow between the knees can help a pregnant woman sleep more comfortably on her side. Also, using a bunched-up pillow or rolled-up blanket at the small of your back may help to relieve some pressure.
It is not uncommon to roll onto your back during the night. Shifting positions is a perfectly natural part of sleep. If you do shift it is possible that the baby’s weight may press on the inferior vena cava, causing discomfort and waking you up.