Nucleated red blood cells: an update on the marker for fetal asphyxia.
OBJECTIVE: Our goal was to update our experience with nucleated red blood cells as a marker for fetal asphyxia and to determine whether a relationship exists between the presence of nucleated red blood cells and long-term neurologic impairment. STUDY DESIGN: Nucleated red blood cell data from 153 singleton term neurologically impaired neonates were compared with cord blood nucleated red blood cells of 83 term nonasphyxiated newborns. Newborns with anemia, intrauterine growth restriction, and maternal diabetes were excluded. The group of neurologically impaired neonates was separated into the following subgroups: group I, persistent nonreactive fetal heart rate pattern from admission to delivery (n = 69); group II, reactive fetal heart rate on admission followed by tachycardia with decelerations and absent variability (n = 47); group III, reactive fetal heart rate on admission followed by an acute prolonged deceleration (n = 37). The first and highest nucleated red blood cell value and the time of nucleated red blood cell disappearance were assessed. RESULTS: The mean number of initial nucleated red blood cells was significantly higher in the group of neurologically impaired neonates (30.3 +/- 77.5, range 0 to 732 per 100 white blood cells) than in the control group (3.4 +/- 3.0, range 0 to 12 per 100 white blood cells) (p < 0.000001). When the group of neurologically impaired neonates was separated on the basis of timing of the neurologic impairment, distinct nucleated red blood cell patterns were observed. Significant differences were obtained between each of the three groups of neurologically impaired neonates and the normal group, with respect to initial nucleated red blood cells (group I, 48.6 +/- 106.9; group II, 11.4 +/- 9.8; group III, 12.6 +/- 13.4; p < or = 0.000002). Maximum nucleated red blood cell values were higher in group I (mean 51.5 +/- 108.9) than in groups II and III combined (mean 12.7 +/- 11.9) (p = 0.0005). Group I also had a longer clearance time (119 +/- 123 hours) than groups II and III combined (mean 59 +/- 64 hours) (p < 0.001). CONCLUSION: Our ongoing study indicates that nucleated red blood cells identify the presence of fetal asphyxia. When fetal asphyxia is present, distinct nucleated red blood cell patterns are observed that relate to the timing of fetal injury. In general, intrapartum injuries are associated with lower nucleated red blood cell values. Thus our data continue to support the concept that nucleated red blood cell levels may assist in determining the timing of fetal neurologic injury.