The edema occurred in the fifth month of pregnancy is considered to be caused by the following reasons: i. The enlarged uterus will compress the inferior vena cava, which will cause edema due to poor venous return. Second, unreasonable dietary structure and partial diet of pregnant women lead to hypoproteinemia, and low plasma osmolality will produce lower limb edema. Third, the increase of blood volume and blood dilution in the body in the middle and late pregnancy will aggravate the low protein edema. During pregnancy, we should pay attention to increasing high-quality protein every day, such as lean meat, eggs and milk, etc. We should also pay attention to exercise, elevate both lower limbs during rest and sleep in the lateral position to reduce edema, and pay attention to exclude pathological edema, such as gestational hypertension, gestational kidney disease and immune system diseases.