Perinatal risk factors associated with severity of haemolytic disease of the foetus and newborn due to Rhc maternal-foetal incompatibility: A retrospective cohort study.

BACKGROUND AND OBJECTIVES Anti-c is the third red blood cell antibody responsible for haemolytic disease of the foetus and newborn (HDFN) requiring intrauterine transfusion. We aimed to identify risk factors associated with HDFN and severe HDFN due to Rhc maternal-foetal incompatibility. MATERIALS AND METHODS A retrospective cohort study was conducted in Paris and the surrounding area (France), between 2013 and 2015. We included mothers and their children managed by the National Reference Centre in Perinatal Hemobiology for alloimmunization and maternal-foetal incompatibility for the Rhc antigen (N = 121). We conducted bivariate analyses to assess a relationship between perinatal factors (e.g., titre and concentration of anti-c antibodies, direct antiglobulin test) and HDFN, its severity and duration. RESULTS The incidence of HDFN was 30% (n = 36), including 11% of severe HDFN (n = 13). Seven percent (n = 9) of neonates received at least one transfusion during the first week and 21% (n = 26) after this period until 3 weeks of life. During pregnancy, a concentration ≥7.5 IU/ml and a titre ≥4 and above were associated with HDFN and severe HDFN (p < 0.05). At birth, the high intensity of the quantitative direct antiglobulin test was associated with HDFN and severe HDFN (p < 0.05). A concentration ≥15 IU/ml is the best factor (area under curve [AUC] = 0.78) in predicting HDFN, followed by a titre ≥8 (AUC = 0.76). CONCLUSION Anti-c alloimmunization causes neonatal anaemia, which is often belated. Paediatricians have to be aware of these risk factors and organize prolonged monitoring of neonates.