Best sleep positions in pregnancy

By the second trimester, sleeping on the left side maximizes blood flow to the placenta by keeping the growing uterus off the vena cava (the large vein returning blood to your heart on the right side). Right side is a close second; alternating is fine. Bend the top knee and slide a pillow between your legs to unload the hips and lower back. A small pillow under the bump provides extra support in the third trimester when the belly gets heavy. Sleeping flat on your back becomes uncomfortable on its own by mid-pregnancy — that's your body's natural signal to switch positions. If you wake on your back, don't panic; just roll to your side. Sleeping on your stomach becomes impossible around 20 weeks and isn't recommended after that anyway.