Early neonatal nucleated erythrocyte counts in preterm deliveries: clinical and pathologic correlations

To determine the relation between the initial neonatal nucleated erythrocyte (nRBC) count and acute infection or ischemia in cases delivered before 32 weeks' gestation.

A set of 465 nonanomalous singleton live births delivered at 22-32 weeks' gestational age (GA) contained 386 cases with a complete blood count obtained by 3 hours of life, including 173 cases of premature rupture of the membranes (PROM) before labor, 143 cases of preterm labor with intact membranes (PTL), and 70 cases of preeclampsia. Maternal and neonatal charts were reviewed. Placental histopathology was scored in the following five categories: acute intrauterine inflammation, uteroplacental vascular lesions, intraplacental vaso-occlusive lesions, chronic inflammation, and coagulation-related lesions. The initial nRBC count (nRBCs/100 white blood cells [WBC] x WBC count/dL) was analyzed.

In PROM and PTL (controlling for GA), the nRBC count was directly related to the maternal WBC count (PTLP = .018), maternal temperature within 24 hours of delivery (PROM P = .014), initial neonatal WBC count (PROM P < .0001; PTL P = .0004), total myeloid elements (PROM P = .005, PTL P = .009), total nonmyeloid elements (PROM P < .0004, PTL P < .0001), and total placental acute inflammatory score (PROM P = .04, PTL P = .02). In preeclampsia, cytotrophoblast proliferation (P = .02), villous edema (P = .008), "hemorrhagic endovasculitis" (P = .04), and histologic abruption (P = .0006) were directly related to the nRBC count. In well-grown, nonacidotic, nondepressed preterm infants, the nRBC count was independent of gestational age, with the 90th percentile at 5229 nRBC/dL.

When preterm PROM and PTL are accompanied by acute ascending infection, nRBC release may be a fetal response to the inflamed environment. In preterm preeclampsia, nRBC elevation marks uteroplacental hypoperfusion.