Baby breast milk does not gain weight for more reasons, clinically common reasons such as indigestion, breast milk nutrition is not sufficient, suffering from certain congenital diseases. 1. indigestion: when the baby indigestion, due to gastrointestinal dysfunction, nutrient absorption is not good, easy to cause the baby although breastfeeding but also not very fat. 2. Inadequate breast milk nutrition: when the mother’s nutrition is insufficient or personal physical reasons, breast milk secretion is insufficient or the nutrient content of breast milk is relatively small, will also lead to the baby is not easy to gain weight, slow physical development. 3. congenital diseases: when the baby suffers from certain diseases, such as congenital heart disease, intestinal malformation and other diseases will lead to the baby’s development is slow, not fat. 4. There are also some reasons such as the baby lack of micronutrients can lead to slow development, not fat. Parents if you find that the baby did not gain weight for a long time, weight did not increase, it is recommended to go to the hospital pediatrics in a timely manner, according to the specific circumstances of the symptomatic treatment.