Mixed feeding babies spit up, mainly due to the immaturity of the infant’s development, or may be due to indigestion, congenital hypertrophic pyloric stenosis and other diseases. 1. Developmental immaturity: Due to the young age of infants, their development is not yet complete, the coordination of swallowing muscle groups is poor, and the volume of stomach content is small. If parents frequently change the formula of milk powder, or mixed feeding, spitting up may occur. 2. Dyspepsia: Dyspepsia may be caused by gastrointestinal dyskinesia, Helicobacter pylori infection and other factors. Symptoms of the child are vomiting, pain in the middle and upper abdomen, etc. When mixed feeding will appear spitting up. 3. Congenital hypertrophic pyloric stenosis: Congenital hypertrophic pyloric stenosis is mainly caused by heredity, abnormal ganglion cell development, hormonal disorders and other factors. Affected children will have vomiting, dry skin and other symptoms, when mixed feeding can aggravate the symptoms of spitting up. Symptoms usually appear around half a month, with projectile vomiting that progressively worsens. Mixed feeding babies spit up, there may also be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.