The most common clinical reasons for the sudden loss of milk during the breastfeeding period are accidental pregnancy, improper diet, mastitis and so on. 1. Accidental pregnancy: If you have an accidental pregnancy during the breastfeeding period, the secretion of progesterone and estrogen in your body will increase, and estrogen will have the effect of returning to the breast, and the increased level of progesterone in your body during the pregnancy will also affect the secretion of milk. 2. Improper diet: If the nutritional intake during lactation is not sufficient, it will cause the body to lack nutrients to produce milk, it is recommended to use more protein-rich beef, eggs, milk and other foods, as well as spinach, tomatoes, apples and other vegetables and fruits. 3. Mastitis: This disease refers to an inflammation of the breast tissue with or without microbial infection. Mastitis during breastfeeding is usually acute, usually associated with bacterial infection, and clinically manifests itself in the form of redness, swelling, warmth, and pain in the affected area, which also results in an abnormal secretion of milk. If these symptoms are present in the clinic, it is recommended to consult a doctor for a clear diagnosis and further treatment if the condition is serious.