Management of pregnancy sensitized with anti-In^b maternal blood donation

Maternal red blood cell (RBC) alloantibodies can cause hemolytic disease of the fetus and newborn (HDFN). Although much is described about common antibodies associated with HDFN, management of a pregnancy complicated by a maternal rare antibody presents several challenges related to assessment of fetal anemia risk, availability of blood for transfusion to the mother and/or the fetus or newborn if needed, and planning for delivery in the case of maternal hemorrhage. Here we report the laboratory medicine workup of a patient who presented for obstetrical care in the United States in the third trimester and had a rare antibody (anti-In^b). Prenatal antibody detection testing demonstrated maternal anti-In^b in a 28-year-old woman (gravida 4 para 1021). Ultrasound could not rule out fetal anemia. Monocyte monolayer assay was performed to assess for the clinical significance of the anti-In^b and revealed that the antibody may be capable of causing accelerated clearance of antigen-positive RBCs. A local and national query revealed that no appropriate units of RBCs were available for either the mother or neonate. Given this information, serial maternal autologous blood donations were performed, and a comprehensive care plan with a multidisciplinary approach for delivery, neonatal management, and preparation for hemorrhage was developed. Published data and our experience suggest that maternal blood donation appears to be a safe and effective way to manage mothers who cannot safely use the community blood supply. Involvement of obstetric, transfusion medicine, anesthesia, and neonatology providers was imperative for a favorable outcome. The antibody did not cause clinically significant anemia in this infant. Immunohematology 2018;34:7–10.