Swelling of legs may be caused by edema during pregnancy, or it may be caused by glomerulonephritis, nephrotic syndrome, right heart failure and other diseases. 1. Edema during pregnancy: when pregnant women are in the middle and late stages of pregnancy, the enlarged uterus will cause obstruction of venous return in the inferior vena cava, and the pregnant women will have edema of the legs, which is a normal phenomenon and no need to worry. 2. Glomerulonephritis: Glomerulonephritis may be caused by heredity, infection, immune abnormality, metabolic disorder and other factors. Patients may have hematuria, edema, proteinuria, fever, joint pain and other symptoms, manifested as swelling of legs. 3. Nephrotic syndrome: The cause of nephrotic syndrome is not yet clear, and it may be caused by factors such as immunity, infection, drugs and heredity. Symptoms include high degree of edema, large amount of proteinuria, weight gain, etc. Patients may have swelling in both legs. 4. Right heart failure: Right heart failure may be caused by infection, overloading of the heart, anemia, ischemia and other factors. Patients may present with symptoms such as abdominal distension, abdominal pain, nausea, vomiting, edema, dyspnea, etc., which are manifested by swollen legs. There are many causes of leg swelling, and patients are advised to go to regular hospitals so as to clarify the causes of the disease. And actively cooperate with the doctor to take relevant treatment measures, so as not to delay the condition.