Utilizing umbilical cord blood – Minimizing blood sampling and pain in healthy infants at risk for polycythemia

Background: Exposure to pain in early life was associated with long term consequences, therefore strategies for minimizing painful procedures in newborns should be employed. The utility and reliability of cord blood CBC was demonstrated before, however data regarding use of cord blood in healthy infants at risk for polycythemia are lacking. Methods: A single-center, paired-sampling prospective laboratory study including all healthy asymptomatic infants born after 36 weeks gestation who were SGA (<2500 g), LGA (>4000 g), or born to mothers with diabetes in pregnancy. Blood count indices were compared between umbilical and neonatal capillary or venous blood samples. In order to predict cut-off values for neonatal polycythemia using umbilical hematocrit, receiver operator curves (ROC) were plotted. Results: Paired samples were collected from 433 infants. Mean gestational age and birth-weight were 39.0 ± 1.3 weeks and 3489 ± 682 g. Hemoglobin, hematocrit and WBC values were lower in cord blood compared to neonatal, but PLT count was higher. Pearson r showed only modest correlation between peripheral capillary and umbilical or venous Hct - 0.35 (p < 0.001), and 0.44 (p < 0.001), respectively. In order to try and capture clinically significant polycythemia ROC was plotted for hematocrit >70% and <40%. In our cohort, using the calculated cutoff values (>51% and <35%) could have resulted in a decrease of 72% of neonatal blood draws. Conclusion: This analysis should be interpreted with caution, as currently it cannot support the routine use of umbilical samples' hematocrits for making treatment decision in newborns at risk for polycythemia. Further larger studies are needed.