Swollen legs and feet of pregnant women may be physiological, mainly related to endocrine changes, obstruction of blood return to the lower extremities, blood dilution; it may also be pathologic, mainly related to hypertensive syndrome of pregnancy. 1. Endocrine changes: the increased secretion of estrogen and aldosterone after pregnancy can lead to water and sodium retention in the body, thus causing edema of the legs and feet. 2. Obstruction of blood return to the lower limbs: As the enlarged uterus in the late stage of pregnancy can compress the inferior vena cava, the blood return to the lower half of the body is obstructed, resulting in elevated venous pressure, which causes edema of the lower limbs. 3. Hemodilution: blood volume increases during pregnancy, but plasma proteins do not increase, so the blood is relatively diluted, plasma colloid osmotic pressure decreases, which causes water to move to the tissue space and edema. 4. Hypertensive syndrome of pregnancy: referred to as hyperemesis gravidarum, its main clinical manifestation is a mild increase in blood pressure, may be accompanied by mild proteinuria and (or) edema, and the edema is mostly started by the ankle, press the depression, and do not see subside after rest. In late pregnancy, pregnant women should try to avoid standing for a long time, rest and sleep can be appropriate to elevate the lower limbs, promote the venous return of the lower limbs, help reduce the occurrence and development of edema. If a pregnant woman has edema not only in her legs and feet, but also in other parts of her body, or if she has high blood pressure, proteinuria, etc., then it is a pathological phenomenon, and she should consult a doctor in time.