Nucleated red blood cell count in the differentiation of fetuses with pathologic growth restriction from healthy small-for-gestational-age fetuses

Objective: The purpose of this study was to evaluate the utility of the neonatal nucleated red blood cell count in differentiating the fetus with growth restriction from the small but otherwise healthy fetus. Study Design: Perinatal outcomes were evaluated prospectively for all neonates admitted to the neonatal intensive care unit in 1997. Nonanomalous neonates with normal phenotype and a complete blood cell count performed within the first 6 hours after birth were included in the study. All neonates with birth weights lower than the 10th percentile for gestational age were considered small for gestational age. Neonates were divided into four groups: small-for-gestational-age neonates with elevated nucleated red blood cell counts, appropriately grown neonates with elevated nucleated red blood cell counts, small-for-gestational-age neonates with normal nucleated red blood cell counts, and appropriately grown neonates with normal nucleated red blood cell counts. Analysis of variance, χ 2 tests, and stepwise regression were used for statistical analysis. Results: Two hundred thirty-seven neonates met the inclusion criteria. Forty-three were small for gestational age. Small-for-gestational-age neonates with high nucleated red blood cell counts had significantly lower umbilical artery pH and were more likely to require mechanical ventilation or blood pressure support agents. Subgroup analysis demonstrated that small-for-gestational-age neonates with elevated nucleated red blood cell counts had significantly more adverse outcomes than did small-for-gestational-age neonates with normal nucleated red blood cell counts. Outcomes of small-for-gestational-age neonates with normal nucleated red blood cell counts were essentially identical to those of appropriately grown neonates. Conclusion: An elevated nucleated red blood cell count may distinguish the fetus with growth restriction from the small but healthy fetus. (Am J Obstet Gynecol 2000;182:1107-9.)