The normal reference range of neonatal bilirubin is <12.9 mg/dl. The clinical significance is as follows: 1. To determine the presence or absence of jaundice and the degree of jaundice Neonatal jaundice is a condition characterized by yellow staining of the skin, mucous membranes and sclera due to abnormal bilirubin metabolism in the blood during the neonatal period, and is the most common clinical problem in newborns. Neonatal bilirubin test is an important indicator for the diagnosis of neonatal hyperbilirubinemia. Currently, there are three methods to detect bilirubin in newborns, namely, venous blood biochemical method, microbilirubin method and transcutaneous bilirubin method. Transcutaneous bilirubin meter is a non-invasive test method, which is convenient to operate and is commonly used in clinical practice. The transcutaneous bilirubin value (TCB) correlates well with the microscopic blood bilirubin value. Since this method is affected by the thickness of the skin and skin color at the measurement site, it may mislead the jaundice situation and can be used as a screening test, and once a certain threshold value is reached, serum blood bilirubin needs to be detected. 2, combined with the serum bilirubin classification to determine the type of jaundice increased serum total bilirubin and unconjugated bilirubin for hemolytic jaundice; serum total bilirubin and conjugated bilirubin increased for obstructive jaundice; serum total bilirubin, conjugated bilirubin and unconjugated bilirubin are increased for hepatocellular jaundice.