An accurate biomarker for metabolic acidosis at birth is needed. Our aims were to investigate the link between umbilical artery pCO and the risk for hypoxic-ischemic encephalopathy (HIE) and to compare false-negative screen results in newborn infants with HIE using three umbilical artery blood gas biomarkers.
From a cohort of newborn infants ≥35 weeks born in Ottawa, Canada, between January 2007 and December 2016, we highlighted those with HIE or who died. We compared the umbilical artery pCO for matched pH>mean versus matched pH≤mean. We compared false-negative rates for three umbilical artery biomarkers – pH<7.0, base deficit≥16 mmol/L and neonatal eucapnic pH≤7.14.
This study included 51 286 newborn infants, 51% male and a mean gestational age of 38.9±1.5 weeks. The rate for HIE or death with umbilical artery pCO for matched pH >mean was 22%, compared to 78% for matched pH ≤mean. In 60 HIE or deaths, the false-negative rate for umbilical artery neonatal eucapnic pH≤7.14 was 8%; compared to 31% for pH<7.00 and 36% for base deficit≥16 mmol/L.
The rate of HIE or death is lower in newborn infants with higher pCO . Using neonatal eucapnic pH decreases the risk of missing newborn infants with HIE.

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