The main causes of edema in pregnant women are: 1, endocrine changes caused by edema during pregnancy, mainly women in pregnancy after the endocrine function has changed, estrogen, aldosterone secretion increased than before, the body’s sodium retention is more, thus causing edema. 2, the lower extremities of the blood reflux is impeded, usually occurs in the twenty-eighth week of pregnancy after the uterus of pregnant women, thus compression of the inferior vena cava reflux caused by poor reflux. 3, due to blood dilution caused by the body, mainly after pregnancy, the increase in red blood cells can’t catch up with the increase in plasma, resulting in plasma protein increases. 3, due to the body of the blood dilution caused by edema, mainly after pregnancy in the body of the red blood cell increase amplitude can not catch up with the amplitude of the plasma increase, resulting in plasma protein increase less, the blood is relatively dilute, plasma colloid osmolality decreased, resulting in edema. 4, hypertensive disorders in pregnancy, hypertensive syndrome in pregnancy is the main reason for pathological edema in pregnancy, the degree of edema is higher than that in pregnancy, and the degree of edema is not as high as that in pregnancy. The degree of edema is heavy, and sometimes it can spread to the whole body.