Physiologic jaundice is a gradual rise in serum bilirubin from 17-51 μmol/L (1-3 mg/dl) at birth to 86 μmol/L (5 mg/dl) or more 24 hours after birth in newborns with clinical jaundice without other symptoms, which subsides within 1-2 weeks. Serum bilirubin for physiological jaundice does not exceed 204 μmol/L (12 mg/dl) in term infants and 255 μmol/L (15 mg/dl) in preterm infants. However, individual preterm infants with serum bilirubin less than 204 μmol/L (12 mg/dl) can also develop bilirubin encephalopathy, and should be alert to physiologic jaundice to prevent misdiagnosis or omission of pathologic jaundice. Pathological jaundice in newborns: 1, jaundice appears early, within 24 hours after birth that jaundice; 2, jaundice is heavy, golden yellow or jaundice throughout the body, palms, soles also have more obvious jaundice or serum bilirubin greater than 12-15 mg / liter; 3, jaundice persistent, 2-3 weeks after birth jaundice is still persistent or even deepen, or alleviate and then deepen; 4, accompanied by anemia or stool color change 5, with abnormal body temperature, poor appetite, vomiting and other manifestations. Pathological jaundice should be taken seriously, because it is often a manifestation of disease, and the cause should be sought. In addition, when the concentration of unconjugated bilirubin reaches a certain level, it can damage brain cells through the blood-brain barrier (often called nuclear jaundice), causing death or sequelae such as cerebral palsy and mental retardation. Therefore, once a child is suspected of having pathological jaundice, he or she should be seen immediately.