Anti-'Mi(a) ' is the most common alloantibody of potential clinical significance in the Taiwanese population. The Mi .III phenotype is rare among Caucasians but has a high incidence in various Oriental populations. We describe a nulliparous woman with no history of transfusions, who had hydrops foetalis at 28 weeks gestation. Foetal haemoglobin was 4.4 g dL(-1) , and a positive direct antiglobulin test was positive in the foetal blood. Intrauterine intravascular transfusion was given, and the baby was discharged healthy. Anti-'Mi(a) ' was identified in the maternal serum, the cord blood serum and the eluate from red cells of the cord blood. Anti-'Mi(a) ' in the maternal serum was confirmed to be anti-Mur. The polymerase chain reaction-restriction fragment length polymorphism method confirmed that both the baby and her father had the Mi .III gene. Therefore, our report documents that anti-Mur has the potential to cause hydrops foetalis.
