Polycythemia in the newborn

Neonatal polycythemia, defined as a venous hematocrit ≥65% (0.65), is a common problem in newborns. Infants born postterm or small for gestational age, infants of diabetic mothers, recipient twins in twin-to-twin transfusion syndrome, and those who have chromosomal abnormalities are at higher risk. Although the cause of polycythemia is often multifactorial, most cases can be classified as having active (increased fetal erythropoiesis) or passive (erythrocyte transfusion) polycythemia. By increasing blood viscosity, polycythemia can impair microcirculatory flow in end organs and can present with neurologic, cardiopulmonary, gastrointestinal, and metabolic symptoms. In this article, we review the pathophysiology, clinical presentation, diagnosis, and management of polycythemia in the newborn.