What Is the Best Position for Sleeping and Lying Down During Pregnancy?
In general, pregnant women should try not to lie flat on their back or directly on their stomach. Lying on your back, especially in the third trimester, causes more work and stress on your heart: In this position, the baby’s weight can put excessive pressure on the inferior vena cava, the large vein that carries blood from the feet and legs, pelvis, and abdomen back to the heart, reducing blood flow to the placenta. In addition, sleeping on your back can actually cause you to have a backache!
Lying on your stomach during pregnancy is not likely to be very comfortable. More importantly, lying on your stomach should be avoided because it can put added pressure on the fetus and reduce blood flow.