Comprehensive Morphological Assessment of Cord Blood: Normal Values and the Prevalence of Morphologically Aberrant Leukocytes

Introduction: Cord blood (CB) is becoming a valuable source for stem cells utilized in a variety of cell therapy applications, as well as for newborn diagnostics. Some parameters of the CB cellular components can be provided by automated analyzers, while others, such as immature or aberrant cells, require blood film morphological assessment. The objectives of the study were to establish normal CB morphology and to determine the prevalence of morphologically aberrant leukocytes in CB. Methods: We performed a comprehensive morphological analysis of 100 CB samples taken from healthy term and appropriate-for-gestational-age neonates born to healthy mothers, preterm neonates, neonates of diabetic mothers, and small-for-gestational-age neonates. Blood counts were assessed, and manual morphological analyses were performed by laboratory specialists. Results: The manual differential count of normal CB samples established the following values: 47.8 ± 10.7% neutrophils, 31.2 ± 9.8% lymphocytes, 10.0 ± 4.0% monocytes, and 3.0 ± 2.5% eosinophils, with no significant sex-related differences. Blasts were observed in 44/100 samples with an average of 0.5 ± 0.7% per sample, and only a minor left shift was observed. There were significant populations of large granular lymphocytes (19.1 ± 10.6% of the total lymphocytes) and morphologically aberrant lymphocytes (12.4 ± 5.4% of the total lymphocytes) in the samples, irrespective of neonatal status. The differentials of preterm CB samples differ significantly from normal term CB samples, including the reverse of neutrophils/lymphocytes ratio, and the lack of basophils. Conclusions: Normal values and unique morphological features in the CB of neonates are described. The abundant morphologically aberrant lymphocytes in CB may represent an immature state of the immune system at birth.