Nine-month-old babies have been diarrhea may be due to indigestion, enteritis and other conditions lead to. 1. indigestion: nine months baby has been diarrhea may be caused by indigestion, if the baby has recently cold or improper diet, indigestion may occur, usually accompanied by abdominal distension, abdominal pain and so on. 2. enteritis: if the nine-month-old baby by bacteria or viruses and other infections may lead to enteritis, will also appear to have been diarrhea, can be accompanied by fever, vomiting, crying and so on. Nine-month-old babies have diarrhea may also have other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.