Association of Hemoglobin Concentration and Cord Blood Cell Characteristics in Healthy Newborn Infants.

Cord blood (CB), used for hematopoietic stem cell transplantation, is readily available from CB banks, and the banking processes are widely standardized. The data collected in CB banks have been utilized to characterize the contents of CB units and, to some extent, the physiological phenomena of healthy newborn infants. The objective of this study was to evaluate the association of the hemoglobin concentration (Hb), whose measurement is independent of the cell counts, with CB cell characteristics (red blood cells, RBC, hematocrit, Hct, mean platelet volume, MPV, platelets, PLT and white blood cells, WBC). The internal associations of cell counts were also evaluated.

The study comprised 167 consecutive ex utero CB collections accepted for processing. All the infants (52% male) were healthy and delivered at term. Of the deliveries 104 (62%) were by Cesarean section. Perinatal data were obtained from the maternity hospital records. The relative birth weight was expressed as a birth weight z-score to normalize the birth weight for gestational age and gender. The median birth weight was 3784 g (range 2490 – 4975) and the median relative birth weight 0.49 SD (-2.41 – 3.37). The mode of delivery did not significantly influence these values. Umbilical artery (UA) pH samples were drawn after delivery as part of routine hospital care. A hematology analyzer utilizing the electronic resistance detection method coupled with volumetric (cell analysis) and colorimetric (Hb) principles was used for cell counting (Sysmex K1000, Sysmex Corp., Kobe, Japan). All the concentrations were standardized to exclude the effect of the varying blood-to-anticoagulant ratio. (Aroviita et al. Acta Paediatr 2004;93:1323-1329) CD34+ cell analysis was performed with a flow cytometer based on ISHAGE guidelines. Two-sided p values <0.05 were considered statistically significant. The CB banking program was approved by the ethical committees of the institutes.

The hematological values and their distributions were within the published ranges. (Nathan and Oski's Hematology of infancy and childhood, 7^th ed. 2009) Hb (median 174 g/L, range 130 – 234) correlated with the RBC concentration (4.70 ×10¹²/L, 3.46 – 6.62; r = 0.96, p < 0.0001), as expected. Interestingly, MPV (8.7 fL, 7.5 – 11.5) correlated with Hb (r = 0.22, p = 0.0043), RBC concentration (r = 0.26, p = 0.0008), and Hct (53.6%, 40.1 – 73.1; r = 0.26, p = 0.0008). The PLT concentration (270 × 10⁹/L, 161 – 607) and plateletcrit (defined as PLT concentration x MPV; 0.24%, 0.15 – 0.48) correlated negatively with Hb (r = -0.31, p < 0.0001 and r = -0.26, p = 0.0008, respectively). Hb also correlated with the WBC concentration (15.1 ×10⁹/L, 5.54 – 39.7; r = 0.23, p = 0.0024). No correlation was observed between UA pH (7.28, 7.04 – 7.4) and the CB cell counts, except for the WBC concentration (r = -0.36, p < 0.0001) and CD34+ cell concentration (43.9 ×10⁶/L, 7.14 - 253; r = -0.37, p < 0.0001). The CB PLT concentration and UA pH differed significantly between vaginal delivery and Cesarean section (p = 0.0053 and p = 0.0002, respectively).

Valuable information about neonatal hematology can be obtained through careful analysis of perinatal and CB banking data. Hb and the cell characteristics of CB reveal strictly controlled internal associations which seem to reflect the general activity of hematopoiesis.

No relevant conflicts of interest to declare.