Five months of pregnancy belongs to the middle of pregnancy, the appearance of running breasts in pregnant women is mostly a normal phenomenon caused by hormonal secretion changes in the body, but it may also be caused by mastitis, breast cancer, etc., and needs to be observed. The common clinical reasons are as follows: 1. Normal phenomenon: In the middle of pregnancy, the lactogen content starts to rise, stimulating the development of mammary ducts and alveoli, resulting in the phenomenon of milk flowing from the nipples, preparing for lactation after delivery, which is a normal phenomenon, as well as the expansion of mammary ducts, areola coloring, areola enlargement and breast swelling and pain. We should pay attention to keep local dryness, cleanliness and hygiene, avoid squeezing nipples with hands, wear loose cotton underwear to reduce local stimulation of breasts, which helps blood circulation and reduce breast discomfort; 2. The symptoms of early stage breast cancer are not obvious, but there may be breast overflow, that is, the phenomenon of running water from the breast. If the diagnosis is confirmed after ultrasound and pathological examination, pregnancy should be terminated at the right time and adjuvant treatment of surgery, radiotherapy and chemotherapy should be given. It is normal to have simple breast discharge in the fifth month of pregnancy without other symptoms, so pay attention to keeping the area clean. If it is accompanied by a lump, it is recommended to seek medical attention promptly to clarify the cause and treat the cause.