Background Para-Bombay blood phenotype is a rare blood group with limited cases reported worldwide. This blood group is characterised by the absence of ABH antigen on red blood cells but presence of ABH secretor substances in the body secretion. This rare phenotype is usually misinterpreted as O and may endanger patient if urgent blood transfusion is required. Case Report A mother who was labelled as Group O Rh D positive during antenatal follow-up was found to have ABO discrepancy during delivery. Baby was admitted for extremely premature delivery at 25 weeks. As the baby required transfusion, problem arose during crossmatching with the mother’s sample. It was found that the mother was group O Rh D positive in forward grouping. However, the reverse grouping showed the presence of reaction (2+) in O cells. Baby was grouped as O Rh D positive. As transfusion was urgently needed due to baby’s unstable condition, group O Rh D positive packed cell was found compatible with baby’s serum, subsequently transfused. Bombay blood donor was contacted, and the donated blood was sent to the hospital for further management. Further investigations were performed, indicating that the mother is Para-Bombay A. Due to recent transfusion to baby, we suggested to repeat baby’s blood group after the baby is 1 year old. Conclusions Para-Bombay was usually mislabelled as O if the sample was not tested with O cell in reverse grouping. Additional tests may be needed during antenatal follow up to prevent complications during delivery which requires emergency blood transfusion.

Background Para-Bombay blood phenotype is a rare blood group with limited cases reported worldwide. This blood group is characterised by the absence of ABH antigen on red blood cells but presence of ABH secretor substances in the body secretion. This rare phenotype is usually misinterpreted as O an...