The low weight of a 9-month-old baby may be due to underfeeding, or it may be due to diseases such as dyspepsia, in addition, it is necessary to be alert to the possibility of congenital heart disease. Food supplementation, medication, surgery and other treatments are available. 1. Insufficient feeding, if the 9-month-old baby’s low weight is caused by insufficient feeding, you need to pay attention to the baby’s diet, give the baby more nutritious food, if the lack of milk can be supplemented with appropriate complementary foods, the baby’s growth and development will have a certain help. 2. indigestion, 9 months baby light weight may also be caused by indigestion, need timely medical examination and treatment, generally can be used under the guidance of the doctor bifidobacteria, lactobacillus and other medication to regulate intestinal flora, help digestion. 3. congenital heart disease, if there is a congenital heart disease may affect the growth and development of the baby’s body, such a situation, you need to actively consult a doctor for examination and treatment, and if necessary, need to carry out surgical treatment. Nine-month-old baby light weight may also be related to other reasons, usually can do regular child health care, follow the doctor’s instructions for diet and feeding, if there is an abnormality, it is best to consult a doctor in a timely manner.