Management of patients with rare blood groups in maternity

We report on our experiences since 2010 with pregnant women with rare blood types. The lack of compatible blood is a challenge for the anaesthetist whose priority is to prevent and treat anaemia in late pregnancy in order to avoid immunisation after transfusion of incompatible blood. In our hospital, the blood type is checked during the first obstetric consult, which is variable, starting from the fourth month of pregnancy. Rare blood types are most often diagnosed in an advanced stage of pregnancy (30 weeks of gestation: WG) due to the late inscription for obstetrics consult, resulting in even later anaesthetic visit. In our 13 patients, the most common blood systems are Duffy, MNS, and RH. 61.5% of the patients have associated antibodies (anti-MNS5). The majority of patients received iron with significant increase of ferritin (17.24 ± 12.95 μg/L versus 262.2 ± 404.4 μg/L, p = .033). Six of the patients had 2-3 injections of EPO between 29 - 36 + 1 WG. There were no transfers for paediatric management of haemolytic disease in the newborn following the birth. Overall, this treatment of patients with a rare blood group has also changed our practices for the follow-up of other pregnant women, and ferritin is more regularly prescribed.Impact statementWhat is already known on this subject? For rare blood groups, the frequency in the general population is less than 1/4000. The most common antibodies at risk of haemolytic disease and 'hydrops fetalis' are anti-D, anti-E, anti-C, and anti-K. The survey of pregnant women with a rare blood type takes into account the maternal risk of 'transfusion deadlock' and haemolytic disease of the newborn.What do the results of this study add? Rare blood types are most often diagnosed in an advanced stage of pregnancy (30 WG) due to the late inscription for obstetrics consults at Maternity. The most common blood systems are Duffy, MNS, RH, and 61.5% of the patients have associated antibodies (anti-MNS5). The most efficient treatment of prenatal anaemia was iron perfusions who allowed significant increase of ferritin and a maternal haemoglobin concentration of 12.1±1.46 g/dL in the ninth month of pregnancy.What are the implications of these findings for clinical practice and/or further research? A pregnant woman with a rare blood group is a situation that requires a technical platform specialised in haemorrhagic risk and a multidisciplinary team, including a blood bank as well as anaesthetic and obstetrical teams, with excellent interdisciplinary coordination.