If it is of recent occurrence and not present since birth , then it may be related to some dietary changes in the child as in this age group different and new foods keep getting added to the diet . However if it is present since birth , you need to get some tests done If it is of recent occurrence and has happened only once or twice , there is no pain and no abdominal distension or vomiting and baby is passing stools on his own , you don't need to do anything but just wait and watch . If it keeps recurring we can give some medication