The effect of clamped and unclamped umbilical cord samples on blood gas analysis

Arch Gynecol Obstet. 2021 Dec;304(6):1493-1499. doi: 10.1007/s00404-021-06076-w. Epub 2021 May 22.


Purpose: Delayed cord clamping for at least 60 s is recommended to improve neonatal outcomes. The aim of this study is to evaluate whether there are differences in cord BGA between samples collected after double clamping the cord or without clamping the cord, when blood collection occurs within 60 s from birth in both groups.

Methods: A cross-sectional study was carried out, collecting data from 6884 high-risk women who were divided into two groups based on the method of cord sampling (clamped vs unclamped).

Results: There were significant decrease in pH and BE values into unclamped group compared with the clamped group. This difference remained significant when considering pathological blood gas analysis parameters, with a higher percentage of pathological pH or BE values in the unclamped group.

Conclusion: Samples from the unclamped cord alter the acid-base parameters compared to collection from the clamped cord; however, this difference does not appear to be of clinical relevance. Findings could be due to the large sample size, which allowed to achieve a high power and to investigate very small numerical changes between groups, leading to a statistically significant difference in pH and BE between samples even when we could not appreciate any clinical relevant difference of pH or BE between groups. When blood gas analysis is indicated, the priority should be given to the timing of blood collection to allow reliable results, to assess newborns status at birth and intervene when needed.

Keywords: Acid–base equilibrium; Blood gas analysis; Cord clamping; Umbilical cord.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Gas Analysis
  • Constriction
  • Cross-Sectional Studies
  • Female
  • Fetal Blood*
  • Humans
  • Infant, Newborn
  • Umbilical Cord*