Objective: To examine whether changes in nucleated erythrocyte (nRBC) counts in the early neonatal period can distinguish between causes of nRBC release.

Methods: From a data set of 465 nonanomalous singleton live births delivered at 22-32 weeks, excluding maternal diabetes mellitus, Rh isoimmunization, and chronic hypertension, 125 cases had a complete blood count with an nRBC count within 3 hours of life and at least one other value obtained within 48 hours of the first. The change in nRBC count per deciliter was calculated (ΔnRBC) and was correlated with entenatal fetal assessment, neonatal outcome variables, and placental histopathology in five catagories: 1) histologic acute intrauterine inflammation, 2) uteroplacental vascular lesions, 3) intraplacental vasoocclusive lesions, 4) chronic inflammation, and 5) coagulation-related lesions.

Results: There were 92 cases (74%) of premature rupture of membranes (PROM) and preterm labor/intact membranes (PTL) and 33 cases (26%) of preeclampsia. In PROM/PTL, multivariate analyses demonstrated that a higher uteroplacental vascular lesion score was related to more stable nRBC counts (P = .009), whereas a higher nonmyeloid count in the initial neonatal white blood cell count was related to a more rapid decrease in ΔnRBC (combined r = 0.54, P < .0001). No features were related to ΔnRBC in preeclampsia.

Conclusion: In PROM/PTL, but not in preeclampsia, patterns of change in the nRBC count in the early newborn period vary with uteroplacental vascular lesions and acute inflammation. This may reflect differences in the mediators of nRBC release (erythropoietin versus cytokines) and in disease acuity.

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Patterns of Change in Early Neonatal Nucleated Erythrocyte Counts in Preterm Deliveries