Jaundice in the Newborns
Physiological jaundice
Most infants develop visible jaundice due to elevation of unconjugated bilirubin concentration during their first week. This common condition is called physiological jaundice. This pattern of hyperbilirubinemia has been classified into two functionally distinct periods.
Phase one- Term infants – jaundice lasts for about 10 days with a rapid rise of serum bilirubin up to 204 μmol/l (12 mg/dL).
- Preterm infants – jaundice lasts for about two weeks, with a rapid rise of serum bilirubin up to 255 μmol/l (15 mg/dL).
- Preterm infants – phase two can last more than one month.
- Exclusively breastfed infants – phase two can last more than one month.
Causes
Mechanism involved in physiological jaundice are mainly:
- Relatively low activity of the enzyme glucuronosyltransferase which normally converts unconjugated bilirubin to conjugated bilirubin that can be excreted into the gastrointestinal tract. Before birth, this enzyme is actively down-regulated, since bilirubin needs to remain unconjugated in order to cross the placenta to avoid being accumulated in the fetus.After birth, it takes some time for this enzyme to gain function.
- Shorter life span of fetal red blood cells, being approximately 80 to 90 days in a full term infant, compared to 100 to 120 days in adults.
- Relatively low conversion of bilirubin to urobilinogen by the intestinal flora, resulting in relatively high absorption of bilirubin back into the circulation.
