The sudden decrease in milk during breastfeeding is mainly related to the following three reasons: First, when emotionally depressed or mentally overstressed, it will affect the release of hypothalamic pituitary hormones, resulting in insufficient milk secretion and causing a decrease in milk. This is mostly a temporary reduction in milk, which can generally be restored to normal after treatment. Secondly, wearing tight chemical fiber underwear can cause local pressure on the nipples, resulting in blockage of the milk ducts and milk stagnation, resulting in a decrease in milk supply. Third, due to the decrease in the number of times the baby sucks on the nipple, which leads to a decrease in lactogen secretion and milk production. Fourth, due to accidental pregnancy during breastfeeding, which leads to hormonal disorders and reduced milk production. All in all, do not panic when there is a sudden decrease in milk, you should go to a regular hospital for medical consultation to clarify the cause of the decrease in milk and actively treat it, which can mostly increase milk production. At the same time, you should wear loose, breathable underwear during breastfeeding and eat more protein and vitamin-rich foods.