Umbilical Cord Oxygen Content and Neonatal Morbidity at Term

Objective The objective of this study was to investigate the relationship between umbilical cord partial pressure of oxygen (pO ₂ ) at delivery and neonatal morbidity. Study Design This is a secondary analysis of a prospective cohort study of term deliveries with universal cord gas collection between 2010 and 2014. The primary composite outcome of neonatal morbidity included neonatal death, meconium aspiration syndrome, intubation, mechanical ventilation, hypoxic-ischemic encephalopathy, and hypothermia treatment. Umbilical artery (UA), vein (UV), UV minus UA (Δ) pO ₂ , and hypoxemia (pO ₂ ≤ fifth percentile) were compared between patients with and without neonatal morbidity. Areas under the receiver-operating characteristic curves were used to assess the predictive ability of pO ₂ . Results Of 7,789 patients with paired umbilical cord pO ₂ , 106 (1.4%) had the composite neonatal morbidity. UA pO ₂ was significantly lower in patients with neonatal morbidity compared with those without (median [interquartile range]: 16 (12, 21) vs. 19 (15, 24) mm Hg, p < 0.001). There was no difference in median UV pO ₂ or ΔpO ₂ between the groups. UA and UV hypoxemia were significantly more common in patients with neonatal morbidity. UA pO ₂ had limited predictive ability for neonatal morbidity (area under the curve: 0.61, 95% confidence interval: 0.6-0.7). Conclusion Although UA pO ₂ is significantly lower in patients with neonatal morbidity, it is a poor predictor of neonatal morbidity at term.