A newborn infant born at 39 weeks develops physiological jaundice. By what mechanism does physiological jaundice of the newborn primarily arise?
Answer and explanation
Correct answer: A. Transient relative immaturity of hepatic bilirubin glucuronosyltransferase
- Step 1: Newborns have increased red cell turnover (higher hematocrit and shorter RBC lifespan of 70-90 days).
- Step 2: Hepatic UDP-glucuronosyltransferase (UGT1A1) activity is physiologically low at birth (approximately 1% of adult levels).
- Step 3: This leads to transient, self-limiting indirect hyperbilirubinemia peaking at days 3-5 of life in term infants.
Answer
Transient relative immaturity of hepatic bilirubin glucuronosyltransferase.
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