Patterns of Bilirubin Conjugation in the Newborn

Abstract

Concentrations of unconjugated bilirubin and bilirubin diglucuronide (measured as alkali-hydrolyzable bilirubin conjugate) have been determined in serum from umbilical cord blood and capillary blood, taken daily during the first five days after birth, in 47 healthy mature infants. Three of these showed an aberrant pattern.

Bilirubin diglucuronide concentrations were higher than adult values in all the infants, probably indicating an inhibition of the excretion of this pigment.

In the main group of infants unconjugated bilirubin concentrations were high. This may be the result of slow irreversible conjugation. An alternative explanation is possible. If an equilibrium of conjugation is present, the high concentrations of unconjugated bilirubin may result from the elevated concentration of conjugate. In the 3 aberrant cases unconjugated bilirubin was lower than in the main group, about adult level. This may be explained by an early development of the conjugating enzyme or by a high uridine diphosphate glucuronic acid/uridine diphosphate ratio in the liver.

Key Words:

• Bilirubin
• glucuronates
• hyperbilirubinemia
• jaundice
• neonatal