The causes of breast milk jaundice include the following: First, it is caused by insufficient secretion of breast milk. A serious shortage of breast milk secretion in the first few days of a child’s life can cause breast milk jaundice. If the amount of breast milk is insufficient, it can cause too little stool formation in the child’s intestines, causing an increase in the hepatic and intestinal circulation of bilirubin in the intestines. After the hepatic and intestinal circulation of bilirubin increases, the level of bilirubin in the blood will rise significantly, causing breast milk jaundice. Secondly, it is affected by the enzymes in breast milk. Because breast milk contains β-glucuronidase, it can convert conjugated bilirubin in the intestine into unconjugated bilirubin, which is then reabsorbed into the bloodstream, causing an increase in bilirubin levels and resulting in breast milk jaundice.