Blood gas values in clamped and unclamped umbilical cord at birth

Abstract

Aim: To determine the reliability of the cord blood gas analysis on the unclamped cord compared to the standard technique of sampling on double clamped cord.

Study design: Prospective observational study conducted on 46 singleton neonates vaginally delivered at term. Matched pairs of umbilical artery and vein blood samples were collected from unclamped cord within 90s after birth and from the same cord after clamping, with the clamping occurring immediately after the first blood collection. A blood gas analysis was performed on each collected sample.

Outcome measures: Arterial and venous blood samples were analyzed for pH, PO2, pCO2, SaO2, hemoglobin concentration (ctHb) and base excess (BE). The values were compared between the two groups (clamped vs unclamped) using a Wilcoxon test.

Results: No significant difference was found in pH, PO2, pCO2, SaO2 and ctHb values on arterial blood between unclamped and clamped cord. The only significant difference was related to BE (p<0.001). For the venous blood, the values of pH, PO2, pCO2 were comparable between unclamped and clamped cord, while the values of SaO2, ctHb and BE were significantly different (p<0.05).

Conclusion: No significant difference was found in almost all the arterial blood gas parameters and in the main venous blood gas parameters between unclamped and clamped cord. Sampling of cord blood for gas analysis may be performed on the unclamped cord right after birth without reducing the accuracy of the analysis.

Keywords: Acid–base status; Cord blood gas; Cord clamping; Fetal oxygenation.