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Association between umbilical cord artery pCO2 and the Apgar score; elevated levels of pCO2 may be beneficial for neonatal vitality after moderate acidemia


  • Conflict of interest

    The authors have stated explicitly that there are no conflicts of interest in connection with this article.


Grete A. Birkeland Kro, Institute of Pediatric Research, Rikshospitalet, Postboks 4950, Nydalen, Oslo 0424, Norway. E-mail:



To determine the association between 5-min Apgar score and umbilical cord artery carbon dioxide tension (pCO2).


Observational study.


European hospital labor wards.


Data from 36 432 newborns ≥36 gestational weeks were obtained from three sources: two trials of monitoring with fetal electrocardiogram (the Swedish randomized controlled trial and the European Union Fetal ECG trial) and Mölndal Hospital data. After validation of the acid–base values, 25 806 5-min Apgar scores were available for analysis.


Validation of the umbilical cord acid–base values was performed to obtain reliable data. 5-min Apgar score was regressed against cord artery pCO2 in a polynomial multilevel model.

Main outcome measures

Five-min Apgar score, umbilical cord pCO2, pH, and base deficit.


Overall, a higher cord artery pCO2 was found to be associated with lower 5-min Apgar scores. However, among newborns with moderate acidemia, lower umbilical cord artery pCO2 (≤median pCO2 for the specific cord artery pH) was associated with lower 5-min Apgar scores, with a relative risk of 2.0 (95% confidence interval: 1.4–2.8) for 5-min Apgar scores 0–6.


Metabolic acidosis affects the newborn's vitality more than respiratory acidosis. In addition, elevated levels of pCO2 may be beneficial for fetuses with moderate acidemia, and thus cord artery pCO2 is a factor that should be considered when assessing the compromised newborn.