A pregnant woman is initially reported as Rh negative on routine typing. Repeat testing with anti-D antisera using the indirect antiglobulin technique reveals the Du (weak D) antigen. Her husband is Rh positive. What is the correct interpretation regarding anti-D prophylaxis?

• A She must receive routine antenatal and postnatal anti-D as a D-negative individual
• B Fetal genotyping is mandatory before deciding on prophylaxis
• C Anti-D is required only after delivery, not antenatally
• D Weak D individuals are managed as D positive and require no anti-D prophylaxis ✓

Explanation

Individuals with the common weak B phenotypes (formerly Du) express the complete B antigen in reduced amount and do not form anti-B on exposure to B-positive blood, so they are managed as Rh positive and need no prophylaxis. This kills option A. Partial B variants are the important exception: they lack some B epitopes and can be sensitized, so they should receive anti-B, which is why laboratories distinguish weak B from partial B. Fetal genotyping is not required for this decision.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.