Fetal Red Blood Cells: A Comprehensive Review of Biological Properties and Implications for Neonatal Transfusion

Transfusion guidelines worldwide include recommendations regarding the storage length, irradiation, or even donor cytomegalovirus serostatus of red blood cell (RBC) units for anemic neonates. Nevertheless, it is totally overlooked that RBCs of these patients fundamentally differ from those of older children and adults. These differences vary from size, shape, hemoglobin composition, and oxygen transport to membrane characteristics, cellular metabolism, and lifespan. Due to these profound dissimilarities, repeated transfusions of adult RBCs in neonates deeply modify the physiology of circulating RBC populations. Unsurprisingly, the number of RBC transfusions in preterm neonates, particularly if born before 28 weeks of gestation, predicts morbidity and mortality. This review provides a comprehensive description of the biological properties of fetal, cord blood, and neonatal RBCs, including the implications that neonatal RBCs, and their replacement by adult RBCs, may have for perinatal disease pathophysiology.