Breasts may become smaller after breastfeeding for a long time, but the degree of change varies from woman to woman, and can be improved by dietary modification and surgery if necessary. After pregnancy, women will stimulate breast development due to changes in estrogen and progesterone levels, and by the time they reach the late stage of pregnancy, their breasts have grown larger, which is in preparation for future breastfeeding. After delivery, due to the need for breastfeeding, milk is produced continuously and the breasts experience repeated filling and emptying. After a long period of breastfeeding, due to the emptying of milk inside the breasts, the mammary tissue gradually degenerates, and the phenomenon of breast shrinkage and sagging will occur, which is generally a normal physiological reaction. Women can eat more high-fat and high-quality protein food, do more breast muscle training, and if necessary, improve the shape of the breasts through breast augmentation with autologous fat or breast implants. To summarize, women’s breasts will become smaller after breastfeeding, and women can consult a doctor in time and follow the doctor’s instructions to improve the conditioning.