Infants do not gain weight, may be related to insufficient milk, may also be due to milk protein allergy, chronic wasting disease and other reasons. 1. Insufficient milk: commonly found in breastfed babies, due to insufficient milk of the mother, but the parents did not find out in time, resulting in long-term insufficient milk intake of infants, resulting in a lack of nutrients in the body, unable to meet the needs of the growth of infants, they may show the phenomenon of weight does not gain. 2. Milk protein allergy: usually due to genetic factors, non-exclusive breastfeeding, or immature development of the infant’s immune system and other reasons, resulting in weakened intestinal barrier function, easily caused by milk protein allergy, resulting in diarrhea, vomiting and other symptoms, in the long run, there may be a baby weight does not increase the situation. 3. Chronic wasting disease: common in congenital multiple organ developmental malformation, congenital heart disease, etc., may lead to the child’s weight does not increase, there may also be feeding difficulties and other symptoms. The lack of weight gain in infants may also be caused by other reasons, it is recommended to seek medical advice as soon as possible, after a clear diagnosis of the cause, to give targeted treatment and adjustment.