Nucleated red blood cells as a marker of acidemia in term neonates

OBJECTIVES: Nucleated red blood cells are produced in increased numbers under hypoxic conditions. We sought to examine the relationship between nucleated red blood cell count in the circulations of term neonates and other possible markers of fetal hypoxia. STUDY DESIGN: We prospectively collected umbilical blood from all live-born neonates delivered at our institution. Arterial blood was analyzed for pH and blood gas values. Venous blood was analyzed for nucleated red blood cell count. We reviewed the medical records for maternal data and neonatal outcomes of gestations of greater than or equal to 37 weeks' duration. RESULTS: We evaluated 1561 cases. The mean nucleated red blood cell count per 100 white blood cells was 9.2 +/- 18.1 (range, 0-327). Nucleated red blood cell counts were higher in infants with pH <7.20 (P = .001). Both patients with respiratory acidemia and patients with uncompensated metabolic acidemia had elevated nucleated red blood cell counts (P = .013 and P = .014, respectively). As umbilical artery pH and base excess decreased, nucleated red blood cells became more prevalent. Elevated nucleated red blood cell counts were associated with presence of meconium (P = .020) and neonatal intensive care unit admission (P = .024). CONCLUSIONS: We found that nucleated red blood cell counts vary widely in the circulation of term neonates. Elevated nucleated red blood cell counts are associated with fetal acidemia, meconium, and neonatal intensive care unit admission.