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An infant's indirect (unconjugated) serum bilirubin level is 10 mg/dL. The exact definition of a physiologic range and management of indirect hyperbilirubinemia is complex and based on many factors, including gestational age (GA), postnatal age, birthweight, disease state, risk factors, degree of hydration, nutritional status, and ethnicity. Total serum bilirubin (TSB) is the sum of direct (conjugated) and indirect (unconjugated) and can be measured in the blood. The indirect bilirubin is calculated by subtracting the direct bilirubin from the total bilirubin. Transcutaneous bilirubin (TcB) is a measurement of total serum bilirubin from an instrument that uses reflectance measurements on the skin and correlates well with the laboratory TSB value.


  1. How old is the infant? What is the gestational age? High indirect serum bilirubin levels during the first 24 hours of life are never physiologic. Hemolytic disease (Rh isoimmunization or ABO incompatibility), congenital infection (eg, rubella, toxoplasmosis), sepsis, occult hemorrhage, and polycythemia are likely causes. The age and gestation of the infant help determine the bilirubin level at which phototherapy should be initiated. The risk of unconjugated hyperbilirubinemia is inversely proportional with GA. In premature infants, hyperbilirubinemia is usually more severe and lasts longer.

  2. Is the infant being breast-fed? Breast-feeding jaundice (early onset) occurs within the first week of life and is probably associated with decreased production or decreased intake of breast milk resulting in caloric deprivation. Breast milk jaundice (late onset) usually occurs after the first week of life into the second to third week. It is secondary to the increased intestinal absorption of bilirubin by the enzyme B glucuronidase, and there may be a familial association. There is a correlation between bilirubin levels and epidermal growth factor concentrations in infants with breast milk jaundice. This may explain the reason for jaundice in these neonates.

  3. What is the family ethnicity? The incidence of neonatal jaundice is increased in infants of Native American Indian, Inuit, Mediterranean (Greece, Turkey, Sardinia), Sephardic Jewish, Nigerian, and Eastern Asian descent. Native Greeks have a higher incidence than Greeks in the United States. The incidence is lower in African Americans. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is more common in many of these groups and may be partially responsible. Immigration and intermarriage have increased the incidence of G6PD in the United States.

  4. Is the infant dehydrated? With dehydration (or weight loss from birth >12%), fluid administration may lower the serum bilirubin level. Additional feedings should be given, if tolerated (milk-based formula is recommended in dehydrated breast-fed infants); otherwise, IV fluids should be given. It is recommended that mothers nurse their infants 8–12 times a day as a minimum for the first few days. For example, a 3-day-old infant is strictly breast-feeding, but his mother's milk has not yet “come in,” so he has lost significant weight and becomes dehydrated. Adequate hydration is essential, but excess hydration will not clear the bilirubin any more quickly, prevent hyperbilirubinemia, or ...

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