The main reasons for the sudden decrease of breast milk include: 1. pregnancy again during breastfeeding, if the lack of proper contraceptive measures during breastfeeding leads to another pregnancy, the secretion of breast milk will suddenly decrease. 2. lactating mother to control weight, excessive dieting or reduce the intake of fat, protein and other nutrients in the diet. 3. lactating mother overworked, poor rest at night, which leads to a decrease of breast milk secretion. 4. Lactating mothers spend less time with their children when they go out for a long time, and their lactation reflex is weakened, which leads to a decrease in breast milk. When the amount of breast milk suddenly decreases, lactating mothers need to analyze the specific causes according to their living and eating habits to ensure the normal secretion of breast milk.