Infants do not gain weight may be caused by malnutrition, improper care, disease factors and so on. 1. Malnutrition: Insufficient breast milk or improper parental feeding, supplemental food is not added in time, may make the baby body nutrient deficiency, will lead to the baby does not grow weight. 2. Improper care: the baby rests in a noisy environment, long time sleep quality is not good, may have an impact on the body’s growth hormone, it will make the baby weight growth. 3. Disease factors: for example, respiratory tract infections, frequent diarrhea, will affect the weight gain, may also be accompanied by cough, fever, abdominal pain and other symptoms. If an infant does not gain weight and is accompanied by other abnormalities, it is recommended that parents take the infant to a doctor for a detailed examination to clarify the specific causes and then treat the condition in a timely manner.