Menstruation is generally referred to as menstruation, and the causes of breast swelling and pain when menstruation is delayed for 5 days are considered to be related to normal phenomena, premenstrual syndrome, pregnancy and other factors. 1. Normal phenomenon: Normal women’s menstruation will be affected by emotions, environment, mental stress and other aspects, so there will be a delay in menstruation, and breast swelling and pain is considered to be related to the rise in hormone levels. 2. Premenstrual syndrome: for women of childbearing age, it may occur before the onset of menstruation, thus physical and mental symptoms and behavioral changes, mainly related to high emotional stress factors, manifested as breast fullness, headache and backache, anxiety and depression, lack of concentration, memory loss and so on. Therefore, if your period is delayed for 5 days and your breasts are full, consider that it is related to premenstrual syndrome (PMS). 3. Pregnancy: For women of childbearing age who experience delayed menstruation with breast tenderness for 5 days, the possibility of pregnancy should be highly suspected. Especially for women who usually have regular menstrual cycles, delayed menstruation with breast tenderness can be clarified through early and early pregnancy as well as blood and urine tests to see if they are pregnant.