Many moms-to-be wonder why they should lie on their left side during pregnancy, so here’s an introduction. To introduce the anatomy of the human body: the large arteries that emanate from the heart and the large veins that return to the heart (vena cava and vena cava) travel right in front of the spine. The hardest piece in the middle of the spine is called the vertebrae, which are rounded and project forward. The blood vessels are well protected by the hard spine as they travel on the surface of the spine in the abdominal cavity. After pregnancy, the uterus grows day by day and occupies a large place in the abdominal cavity. The uterus contains the fetus, placenta and amniotic fluid and is therefore heavy. When we lie on our backs, the weight of this heavy uterus presses against the posterior abdominal wall. In the center of the posterior abdominal wall is the forward projecting spine, and on the surface of the spine are our vena cava and vena cava. Thus the vena cava and vena cava are compressed. The walls of the vena cava are very thick, and although they are compressed, they have a certain degree of resistance, plus the blood in the lumen is pumped from the heart, so the blood can still flow to the abdominal cavity and the lower extremities. The walls of the vena cava are thinner and less elastic, and its blood flows from the abdominal cavity and lower extremities to the heart, which also lacks power. When the vena cava is compressed, the blood that cannot flow back to the heart stagnates in the abdominal cavity and lower limbs, and the organs with the highest blood flow are the first to experience problems: the uterus, which has the highest blood flow, and the placenta, which has the highest blood flow, and so the placenta is the first to experience problems: stagnation of blood flow in the placenta, causing separation of the placenta from the wall of the uterus, which is known as placenta previa. Placental abruption usually occurs during sleep. Placental abruption is very dangerous for both the fetus and the mother. In severe cases, the life of the fetus can be jeopardized and the pregnant woman may have her uterus removed. Knowing this, after pregnancy, we need to develop the habit of lying on the side. The left side lying position is the main one, you can also lie on the right side, try to avoid the supine position.