1.After the compression of the inferior vena cava by the giant uterus, the blood pressure often drops abruptly, and when the blood pressure is very low, it even compresses the aorta), which is caused by the abrupt reduction of the vena cava return blood volume, while the heart volume is slightly reduced. 2. The distal blood flow of the section of the inferior vena cava compressed by the huge uterus can flow back to the heart via the superior vena cava through the odd vein, thus obtaining partial compensation of the venous return blood volume, and the blood pressure drop can be insignificant. However, there are more anatomical malformations of the odd vein (generally unpredictable), so the sudden drop of blood pressure is often especially obvious in patients with poor compensation of the odd vein return, which obviously increases the degree of danger. 3, To reduce the compression of the inferior vena cava by the huge uterus, the mother after epidural anesthesia for cesarean delivery should change to a supine position with the right side padded 20 degrees in order to deviate the uterus to the left from the inferior vena cava. Normally, pregnant women in late pregnancy, when taking supine position, the whole huge uterus presses on the inferior vena cava and abdominal aorta in front of the spine, and the pregnant women cannot adapt to this disturbance of reduced cardiovascular blood return and must automatically change to lateral position. In the lateral position, the huge uterus leaves the inferior vena cava and abdominal aorta in front of the spine. After the epidural anesthesia takes effect, the lining effect of the abdominal muscle on the huge uterus is eliminated, and in the flat supine position, the huge uterus is enough to completely compress the inferior vena cava and abdominal aorta, so it is especially easy to have a sudden drop in blood pressure, and the woman can still get compensated in the odd vein with good flow; if the woman’s odd vein has poor compensatory flow, the woman can fall into a state of severe shock. Therefore, it is clinically emphasized that after epidural anesthesia, the woman must be placed in a 20-degree supine position on her right side to keep the inferior vena cava away from the compression of the giant uterus. Prevention and treatment of hypotensive syndrome in the supine position: 1. Before cesarean delivery, we should routinely and carefully inquire about pregnancy position preference and discomfort after changing position, especially for large fetuses, twin pregnancies, obese women and women with weakness. 2.Before using local anesthetic in the epidural cavity, 1000ml of crystalloid should be infused rapidly through the upper limb vein to expand blood volume, and if necessary, 10mg of ephedrine can be injected intramuscularly to prevent hypotension. 3.After the injection of local anesthetic, the surgical bed should be tilted to the left side by 20°~30° to reduce the compression of the uterus on the inferior vena cava. 4.Once SHS occurs, the following measures should be taken: ① oxygen by face mask; ② speed up the infusion rate, and if the infusion is through the lower limbs, immediately change the infusion through the upper limbs to enhance the superior vena cava reflux; ③ intravenous injection of ephedrine, but it is not advisable to use methoxamine or neofolin, which has synergistic effect with oxytocin, to avoid sudden rise of blood pressure; ④ strive to remove the fetus as soon as possible to degrade the compression of the uterus on the inferior vena cava; ⑤ do Resuscitation of neonatal distress.