Objectives To investigate associations between nucleated red blood cell (NRBC) counts of neonates with hypoxic-ischemic encephalopathy (HIE), acute perinatal sentinel events, and neurodevelopmental outcomes. We also examined the mechanism causing elevated counts.
Study design We included newborn infants with HIE treated with therapeutic hypothermia (TH) with ≥ three NRBC counts during their neonatal intensive care unit hospitalization and neurodevelopmental evaluations at 24±6 months.
Results Ninety-five (63%) of 152 infants meeting study criteria had normal NRBC counts after birth, defined as ≤95th percentile of the upper reference interval, whereas 57 (37%) had elevated counts. Documented sentinel events during labor resulting in emergency delivery (e.g., acute abruption) (n=79) were associated with normal NRBC counts (odds ratio 257; 95% CI, 33 – 1988). Of the 152 infants evaluated, 134 (88%) survived to discharge. When the first NRBC count was normal, the odds of surviving were three-fold greater (OR 3.0; 95% CI, 1.1 – 8.3) than when it was elevated. Normal counts were moderately predictive of infants without neurodevelopmental impairment at two-year evaluation (p<0.001). The NRBC half-life was longer in those with elevated versus normal NRBC counts, 60 versus 39 hours (p <0.01).
Conclusions In infants with HIE, a normal NRBC count after birth was associated with acute intrapartum events necessitating emergent delivery. Normal counts were modestly predictive of a better prognosis. We speculate that elevated NRBC counts at birth resulted from hypoxia that occurred earlier or chronically. Impaired clearance of NRBC from the blood might be one mechanistic explanation for the high counts.