The Newborn with Hematologic Abnormalities

Key Points Hematologic disorders in neonates are distinct from those in older children due to the ongoing nature of erythropoiesis and hemostasis, as well as the unique developmental physiology of newborns.The diagnosis of most hematologic disorders is based on reference ranges for the newborn and must account for gestational and postnatal age, as variation in normal hematologic values is higher in the neonatal period than at any other time of life.Neonatal anemia can be caused by blood loss, hemolysis, or decreased red cell production. Physiological anemia of the full-term newborn occurs between 6 and 12 weeks after birth and is not a pathological state. Anemia of prematurity is common in preterm infants, often requiring iron supplementation. Alloimmune hemolytic disorders, such as RhD and ABO incompatibility, are leading causes of hemolysis in neonates.Polycythemia in neonates, caused by increased erythropoiesis or erythrocyte transfusion, can result in serious complications from increased blood viscosity and impaired microcirculation.Hemostatic disorders in newborns, whether inherited or acquired, can be challenging to diagnose, as many coagulation protein concentrations are age dependent. Thrombocytopenia and thromboembolic disorders are common in sick neonates and are more often acquired than inherited.Vitamin K deficiency bleeding (ie, hemorrhagic disease of the newborn) is a significant concern in neonates, particularly in those who do not receive prophylactic vitamin K at birth. Bleeding manifestations in the classic form occur 2 to 7 days after birth in exclusively breastfed infants and are common without prophylaxis.Thrombocytopenia in neonates may result from immune-mediated mechanisms (eg, neonatal alloimmune thrombocytopenia [NAIT]), placing neonates at risk for severe bleeding, including intracranial hemorrhage.Neutropenia in neonates is often linked to maternal immune conditions and infections and, less commonly, genetic disorders of production. The risk of sepsis is significantly increased, and severe cases may require treatment with granulocyte colony-stimulating factor (G-CSF).