Why does severe ABO blood type incompatibility in a neonate typically cause hyperbilirubinemia after birth, rather than significant acute hemolysis in utero?

💡 Explanation

Hyperbilirubinemia arises because maternal IgG antibodies, while capable of crossing the placenta, are cleared by the maternal liver during pregnancy, preventing significant bilirubin buildup in fetal circulation. Therefore, significant hyperbilirubinemia only manifests after birth when the neonate's liver is immature and overwhelmed, rather than in utero when maternal clearance occurs.

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