Perinatal clinical management of a rare ABh variant blood group.

Background: The H antigen, precursor of the A and B blood groups, is a high-prevalence antigen. Very few H antigen-negative (H-) blood donors are available in the United Kingdom.

Case presentation: We present the case of a second pregnancy in a 28-year-old woman with the very rare AB_h phenotype, and the presence of anti-H, anti-A and anti-B. Only H- (O_h) and AB_h phenotype red cells were compatible. Given the rarity of individuals with these phenotypes, there were insufficient compatible red cell units for management of a major antepartum or postpartum haemorrhage. For this high-risk pregnancy, meticulous multidisciplinary team (MDT) planning took place between haematologists, obstetricians, anaesthetists, hospital laboratory staff and multiple teams within National Health Service Blood and Transplant including the National Frozen Blood Bank, Rare Donor Team and Red Cell Immunohaematology Laboratories. The MDT produced a birth management plan for various eventualities where blood transfusion may have been required. This process included the creation of our hospital's first vaginal cell salvage policy. A successful routine vaginal delivery was managed without transfusion.

Conclusion: This case highlights the optimal care of a woman with an extremely rare blood group in pregnancy. The principles of management described here are also more widely applicable to women in whom transfusion is contraindicated, undeliverable or declined for other reasons.