ABO isoimmunization of newborn

This code signifies a hemolytic disease of the newborn caused by an incompatibility between the mother's and infant's ABO blood types. Maternal antibodies cross the placenta, attacking the infant's red blood cells, leading to hemolysis and hyperbilirubinemia. This condition is typically less severe than Rh isoimmunization.

Assign this code when documentation confirms ABO incompatibility as the cause of hemolytic disease in a newborn. This diagnosis is supported by laboratory findings such as a positive direct antiglobulin test (DAT) in the infant, elevated unconjugated bilirubin, and evidence of hemolysis. It is often seen in infants of O-type mothers with A or B-type infants.

• Do not confuse this with Rh isoimmunization (P55.0), which involves Rh factor incompatibility.
• Always sequence this code as the principal diagnosis when it is the primary reason for admission or treatment.
• Ensure documentation specifies "ABO isoimmunization" or "ABO incompatibility" and not just "hemolytic disease of newborn" without further specificity.