Serologic investigation and management of an antibody screen negative para-Bombay phenotype during pregnancy.

Background: Individuals with Bombay and para-Bombay red blood cell (RBC) phenotypes produce anti-H antibodies associated with acute haemolytic transfusion reactions. The rarity of compatible donor units creates unique logistical challenges, especially during pregnancy as the onset of labour and fetal distress can occur without warning.

Case report: A 24-year-old female at 38 weeks gestation presented with breech fetal position and reported anti-H antibodies. Critically, the in-house antibody screen was negative by automated solid-phase red cell adherence (SPRCA), while manual testing subsequently demonstrated anti-H antibodies. Forward typing with Ulex europaeus lectin confirmed the absence of H-antigen on RBCs, while Lewis phenotyping and saliva neutralisation revealed H-antigen in secretions, consistent with the para-Bombay phenotype. Three frozen Bombay RBC units were obtained from a nationwide search, and four cross-match compatible non-Bombay (O-positive) units were also prepared. An external cephalic version (ECV) was originally planned since vaginal delivery carries lower bleeding risk than caesarean section (CS). However, acknowledging the unpredictability of ECV, the challenge of timing thawed units, and the possibilities of massive haemorrhage versus wasting rare donor blood, an elective CS was ultimately preferred. Delivery was uneventful without transfusion needs.

Conclusion: This case highlights key considerations regarding serologic identification, blood product management, and interdisciplinary clinical decision-making for patients with Bombay and para-Bombay phenotypes. First, automated SPRCA testing may provide false negative results for anti-H antibodies. Second, backup transfusion strategies for para-Bombay patients may include non-Bombay RBCs. Finally, the procurement, preparation, and use of rare blood products requires thoughtful deliberation between multiple care providers.