After identifying a maternal alloantibody in serum, what is the next logical step in management?

• A. Administer RhIg to mother
• B. Perform paternal genotyping
• C. Titrate the maternal antibody
• D. Perform cord blood typing

Answer: (C)

When a maternal alloantibody has been identified, the immediate next step is to determine how strong and potentially harmful it could be by titrating it. Titration involves testing serial dilutions of the mother’s serum against red cells with known antigen status to find the highest dilution at which the antibody still reacts. This titer tells us whether the antibody is likely to cause clinically significant fetal hemolysis. A low or stable titer generally indicates lower risk and allows routine monitoring, while rising or high titers point to potential fetal anemia and require closer surveillance, such as fetal Doppler assessments and planning for possible in utero intervention or delivery decisions.

Rh immunoglobulin administration isn’t appropriate once an alloantibody has been identified, because the mother has already mounted an immune response. Paternal genotyping and cord blood typing have roles in broader management, but they’re not the immediate next step before ongoing prenatal assessment.