Jaundice visible to the naked eye can occur in neonates with blood bilirubin above 5-7 mg/dl (adults above 2 mg/d1). Some cases of high unconjugated bilirubin (indirect bilirubin as indicated by the test report) may cause bilirubin encephalopathy (nuclear jaundice), with a high mortality rate in severe cases and sequelae in survivors. Physiological jaundice (physiologicaljaundice) is due to the characteristics of neonatal bilirubin metabolism, about 50%; 60%; of term infants and 80%; of premature infants appear physiological jaundice, which is characterized by: ① general good condition; ② term infants jaundice 2-3 days after birth, 4-5 days to reach the peak, 5-7 days to subside, no later than 2 weeks; premature infants jaundice Most of the jaundice appears 3-5 days after birth, peaks in 5-7 days, and subsides in 7-9 days, with a maximum delay of 4 weeks; ③ daily serum bilirubin elevation is less than 85umol/L (5mg/d1); ④ serum bilirubin is less than 221/umol/L (12.9mg/d1) in full-term infants and <257umol/L (15mg/d1) in preterm infants. Pathologic jaundice (pathologicjaundice): ① jaundice within 24 hours after birth; ② serum bilirubin >;22lumol/L (12.9mg/d1) in term infants, >;257umol/L (15mg/d1) in preterm infants, or a daily rise of more than 85umol/L (5mg/d1); ③ duration of jaundice More than 2 weeks in full-term infants and more than 4 weeks in preterm infants; ④ jaundice receding and reappearing; ⑤ serum conjugated bilirubin more than 34umol/L (2mg/d1). Any one of these can be diagnosed as pathological jaundice. Pathological jaundice is caused by a variety of reasons, clinical disease is often dominated by a cause, for ease of description can be divided into three categories: 1, excessive bilirubin production. 2, low liver uptake and/or conjugated bilirubin function. 3, impaired bile excretion.