 Hello, I am Dr. Himali Tekani, I am a consultant obstetrician and gynecologist at Manipal Hospital's Old Airport Road, Bangalore. In early pregnancy, the womb and the developing baby inside are very small to cause any pressure over any of the organs and hence sleeping in any direction, either any side or lying on the back would not cause any problems at all. As the pregnancy advances, the baby inside grows and so does the mass and volume of the womb. This theoretically speaking could cause pressure on some of the large blood vessels of the body which carry blood from the legs towards the heart and hence pressure on these could lead to swelling in the legs. Now that's why we usually tell patients to sleep on the sides during pregnancy but once you are sleeping, you may change positions and that is fine. So ideally speaking, sleeping on the sides is the best sleeping position during pregnancy. Whether it may be on the left or on the right, a lot of women have reflux during pregnancy so for these women we recommend trying to sleep with a little propped up position, putting two pillows under their head. For women who find difficulty in sleeping on the side, putting pillows between their knees or on the sides and taking support would help ease out and help sleep on the side. Also sleeping on the sides would relieve backache for such women.