Can Fetal Umbilical Venous Blood Be a Reliable Source for Admission Complete Blood Count and Culture in NICU Patients?

Background: Minimizing initial neonatal blood draws and their associated pain is important. The placenta has ample fetal blood that is otherwise discarded; obtaining admission laboratory evaluations from fetal umbilical venous blood (FUVB) may provide a suitable alternative.

Objective: We hypothesized that obtaining an aerobic bacterial blood culture (BCX) and a complete blood count with manual differential (CBC/diff) from FUVB is feasible and yields results comparable to those obtained directly from the neonate.

Study Design: BCX and CBC/diff were attempted on paired samples from FUVB (in the delivery room) and neonatal blood (shortly after NICU admission) of 110 patients. The paired t test, Pearson's correlation coefficient (R), and multivariable linear regression were used for data analysis.

Results: Positive BCXs were found in 9 of 108 FUVB samples compared to 1 of 91 neonatal samples. Three out of 9 FUVB cultures were true pathogens, including 2 Escherichia coli and 1 viridans group streptococcus, all with negative corresponding paired neonatal cultures. There was 1 positive neonatal BCX, E. coli, with a negative paired FUVB culture. Neonatal hemoglobin (Hb), platelets (PLT), and white blood cells (WBC) all significantly (p < 0.0001) correlated with the paired FUVB samples (R = 0.50, 0.49, and 0.84, respectively). Hb, PLT, and WBC values were clinically comparable but statistically higher in neonatal blood (the differences were 2.3 g/dL, 30,000 cells/μL, and 2,800 cells/μL, respectively; p < 0.007 for all comparisons).

Conclusions: FUVB is suitable for obtaining CBC/diff. FUVB is an appropriate second source for BCX as it yields additional true pathogens. Our findings may support the presence of "culture-negative sepsis" in some neonates.