As the uterus and fetus grow, the sleeping posture of pregnant women becomes more and more important, especially in the third trimester of pregnancy, that is, between 7 and 9 months of pregnancy. Poor sleeping posture will not only affect the contraction of the uterus, but also affect the position of the uterus. It will increase the pressure of the pregnant uterus on surrounding tissues and organs, affecting the blood flow of the uterus and placenta. The fetus exchanges gases and substances with the mother\’s body through the placenta, obtains oxygen and nutrients, and excretes carbon dioxide and waste. Is the placental blood flow sufficient?