Pathologic Unconjugated Hyperbilirubinemia, Isoimmunization, Abnormalities of Red Cells and Infections

Unconjugated hyperbilirubinemia in the newborn after birth is a normal phenomenon, transitional in nature, and harmless. It may be protective for the human neonate exposed to increased levels of oxygen and light in the environment outside the womb before antioxidant enzymatic defenses are fully upregulated. The phenomenon is called “physiologic neonatal jaundice” and the contributing biochemistry has been described in the preceding chapter (see Chapter 81).