Breastmilk does not spoil unless it is expressed. The mother’s breast is a sterile place, and the milk will not be contaminated by pathogenic microorganisms in the breast, so naturally there will be no deterioration. Breast milk is the best food for children, on the one hand, because the various nutrients in breast milk are well-matched, which is very good for baby’s digestion and absorption, and can meet the needs of baby’s growth and development; on the other hand, breast milk is always at a constant temperature in the mother’s breast, and stored in a sterile environment, so it will not be contaminated by pathogenic microorganisms and will not deteriorate, and babies will not get sick after eating breast milk. However, if breast milk is stored in the breast for too long, it will easily lead to insufficient secretion of breast milk.