What is a key reason all newborns experience mild unconjugated hyperbilirubinemia?

Newborns commonly experience mild unconjugated hyperbilirubinemia primarily due to immature hepatic enzyme activity. In the first few days of life, the liver, which is responsible for conjugating bilirubin, has not yet fully matured. This immaturity leads to a reduced ability to process bilirubin efficiently, resulting in increased levels of unconjugated bilirubin in the bloodstream.

This phenomenon, often referred to as physiological jaundice, typically occurs within the first week after birth and is considered a normal adaptation as the liver matures and improves its function. The peak of this hyperbilirubinemia usually occurs around the third to fifth day of life.

The other options are less relevant in this context. High iron turnover is not a primary factor in the development of hyperbilirubinemia in newborns. Low hemoglobin levels can contribute to jaundice in certain conditions, but it is not a general reason for the physiological jaundice seen in all newborns. Excessive breast milk consumption does not cause hyperbilirubinemia; rather, some breastfed infants may experience a specific type of jaundice called "breast milk jaundice," which is due to factors in the breast milk affecting bilirubin metabolism, but this is not the underlying