Neonatal jaundice

What it is

Neonatal jaundice is a sign, not a Dx. The first split is conjugated or unconjugated (direct or indirect). The usual newborn form is an unconjugated hyperbilirubinemia caused by the short lifespan of erythrocytes in the newborn and by insufficient hepatic bilirubin metabolism, due to immature UDP-glucuronosyltransferase. Physiological neonatal jaundice is a diagnosis of exclusion: laboratory tests should first rule out all pathological causes of neonatal jaundice. One rule is fixed - jaundice in a term newborn less than 24 hours old is always pathologic, and for exams it is always hematological. So a term newborn who is jaundiced before 24 hours of age is never read as physiological and never watched: the rule makes it pathologic, and the laboratory tests that rule out the pathological causes come first. It is called jaundice at a total serum bilirubin concentration above 5 mg/dL or above 85.5 micromol/L, and the physiological form is harmless and appears in most infants between the second and the eighth day of life.