A Guide to Terminology for Rh Immunoprophylaxis

Area of Science:

• Hematology
• Immunology
• Genetics

Background:

• Rh hemolytic disease of the fetus and newborn (HDFN) pathophysiology was initially studied in rhesus monkeys.
• The human D antigen, responsible for HDFN, is related but distinct from the rhesus monkey antigen.
• Evolving Rh blood typing terminology impacts clinical management.

Purpose of the Study:

• To review current Rh blood typing terminology.
• To provide guidance on managing Rh-negative women, particularly those with weak D phenotypes.
• To explain the rationale behind changes in Rh blood typing nomenclature.

Main Methods:

• Review of scientific literature on Rh blood group antigen.
• Analysis of RHD genotyping techniques for classifying weak D phenotypes.
• Examination of clinical implications for Rh immunoprophylaxis.

Main Results:

• Serologic weak D phenotype can be further classified as weak D type or partial D phenotype by RHD genotyping.
• Weak D types 1, 2, and 3 are managed as Rh-positive.
• Partial D phenotypes may present as serologic weak D and can form anti-D antibodies, posing a risk for HDFN.

Conclusions:

• Pregnant women with a serologic weak D phenotype require RHD genotyping to determine Rh status.
• Advances in Rh typing necessitate updated obstetrician understanding for effective Rh immunoprophylaxis.
• Consistent terminology and accurate Rh typing are essential for preventing HDFN.