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 neo natal nucleated red blood cell count in differentiating the fetus with grow th restriction from the small but otherwise healthy fetus. STUDY DESIGN: Perinatal outcomes were evaluated prospectively for all neona tes admitted to the neonatal intensive care unit in 1997. Nonanomalous neon ates with normal phenotype and a complete blood cell count performed within the first 6 hours after birth were included in the study. All neonates wit h birth weights lower than the 10th percentile for gestational age were con sidered small for gestational age. Neonates were divided into four groups: small-for-gestational-age neonates with elevated nucleated red blood cell c ounts, 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 blo od cell counts. Analysis of variance, chi(2) tests, and stepwise regression were used for statistical analysis. RESULTS: Two hundred thirty-seven neonates met the inclusion criteria. Fort y-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-gest ational-age neonates with elevated nucleated red blood cell counts had sign ificantly more adverse outcomes than did small-for-gestational-age neonates with normal nucleated red blood cell counts. Outcomes of small-for-gestati onal-age neonates with normal nucleated red blood cell counts were essentia lly 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.