Which of the following blood group antigens is associated with an increased risk of hemolytic disease of the newborn (HDN) due to its high immunogenicity?

A K1 antigen ✓
B Fy(a) antigen
C Jk(a) antigen
D S antigen

Explanation

The K1 antigen is highly immunogenic and can cause an immune response in pregnant women, leading to an increased risk of HDN.

Source

National Institute of Child Health and Human Development (NICHD) studies
Hematology Hematology: Blood Grouping and Crossmatching Hematology: Blood Grouping and Crossmatching Hard MEDICAL Confidence: high