Nucleated red blood cells in the fetus and newborn

Abstract

nRBCs are commonly found in neonatal blood. Increased counts are often the result of prematurity, increased erythropoiesis from chronic conditions, acute stress mediated release from the marrow stores, and postnatal hypoxia. Extreme increases may occasionally be idiopathic. When increased nRBC counts are seen with acute and subacute asphyxia, the magnitude of the increase is a function of the severity and duration of the asphyxia. However, there is a large overlap between the nRBC values after acute, subacute, and chronic asphyxia; asphyxia of any duration does not always cause an increased nRBC count, and extreme increases may be found without asphyxia. Newborn nRBC counts should not be relied on as the sole determinant of the severity or duration of intrauterine asphyxia.