Clinical practices and outcomes of RhD immunoglobulin prophylaxis following large‐volume fetomaternal haemorrhage in Queensland, Australia

Background: Guidelines for laboratory assessment of fetomaternal haemorrhage (FMH) was published by the Australian and New Zealand Society of Blood Transfusion (ANZSBT) in 2002. However, data on adherence by practitioners and clinical outcomes are lacking. Aims: The primary objective is to examine the follow-up testing and dosing of additional RhD immunoglobulin in RhD negative women who experienced large-volume FMH for whom additional intravenous RhD immunoglobulin was requested in Queensland, Australia. The secondary objectives are to examine the rate and risk factors of RhD alloimmunisation in these women. Materials and Methods: RhD negative women with FMH >6 mL for whom additional dose(s) of intravenous RhD immunoglobulin was requested through Australian Red Cross Lifeblood from February 2007 to February 2018 were identified. For each patient, the volume of FMH, methods and timing of FMH quantitation, dose of RhD immunoglobulin, maternal and cord blood groups were analysed against the corresponding antibody screen and identification. Results: Following FMH >6 mL, only 15% and 11.5% of cases adhered to current ANZSBT guideline on follow-up testing and supplemental RhD immunoglobulin dosing respectively. Despite the provision of single supplemental RhD immunoglobulin at a ratio of 100 IU to 1 mL fetal red cells, the rate of RhD alloimmunisation in RhD negative women with RhD positive fetus or fetus of unknown RhD status following FMH >6 mL is at least 4%. Conclusions: Poor compliance with guidelines for follow-up and management of large-volume FMH may contribute to increased risk of RhD alloimmunisation. Further analysis of data is warranted.