More than 40 days baby spit spit with physiological factors and pathological factors (upper respiratory tract infection, gastroesophageal reflux). 1. Physiological factors: more than 40 days the baby salivary glands began to develop, there will be a small amount of saliva in the mouth, but due to more than 40 days the baby swallowing function is not yet mature, can not swallow all the saliva, in the breath between the saliva will be spit out. 2. Pathological factors: due to bacterial or viral infection of the upper respiratory tract leading to nasopharyngeal inflammation, may lead to nasal congestion, poor respiration, which will cause more than 40 days baby spit. Or due to the baby’s lower esophageal sphincter dysfunction appears low pressure, resulting in gastroesophageal reflux, causing the baby to spit. More than 40 days baby spit up, there may be other reasons, it is recommended to go to the hospital, complete the examination to determine the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.