The effects of time on pH and gas values in the blood contained in the umbilical cord

BACKGROUND: The pH and gas analysis of umbilical cord blood is an accepted practice in most maternity hospitals. The data that is obtained after a latency period in processing the cord blood samples is evaluated to determine whether it is useful for the clinic. METHODS: The umbilical cords from 50 term infants were clamped immediately after delivery. Samples of artery and vein blood were drawn 5, 60, and 120 min postpartum and pH, pO2, and pCO2 levels were measured. RESULTS: No significant differences were found after 60 min in the average values for pH in the arterial and venous paired samples, though the arterial and venous pCO2 values declined significantly. The arterial pO2 values increased significantly. After 120 min, no significant differences in the average values for the venous pH and pO2 paired samples were found. The arterial pH values increased significantly, however, and the arterial and venous pCO2 values declined significantly. The arterial pO2 values increased significantly. CONCLUSIONS: Though statistically significant differences occurred over time, these changes were so modest clinically that the data could still be used even when an immediate analysis of the umbilical cord was not possible.