Recurrent fetal hydrops with maternal M alloimmunisation: not a benign condition.

Haemolytic disease of the fetus and newborn (HDFN) is associated with red cell antibodies. Anti-M usually results in a mild haemolysis and is rarely clinically significant. There is no established consensus on management of pregnancies with anti-M. A case of recurrent HDFN with maternal M alloimmunisation was identified at a tertiary hospital in Australia. We collected the patient and neonate's clinical and pathological data and interpreted the case with available literature. This is the first case in literature of recurrent fetal hydrops in the setting of M alloimmunisation. Neonate was delivered in a poor condition, intubated and admitted to the neonatal intensive care unit for ionotropic support, red cell transfusion and plasma transfusion for coagulopathy. Direct Coombs test was positive, confirming HDFN. Although anti-M rarely causes HDFN, accurate history, fetal surveillance and monitoring is essential for identification of fetal anaemia. Concurrent placental disease may increase fetal risk from anti-M antibodies.