Risk of Neonatal Adverse Outcomes Linked to Umbilical Cord pH Levels Above 7.00, suggests research

Clinical practice is mainly oriented to umbilical cord pH as an indicator of neonatal well-being, where values below 7.00 are considered to indicate severe acidosis with heightened risks to health. Evidence supporting this threshold is inconsistent and often based on selective populations; therefore, the association may not be universal. This study assessed the association of various UC-pH levels with neonatal outcomes within a national population of full-term, singleton infants born in Denmark.

This population-based cohort study retrospectively included 340,431 liveborn, singleton, full-term infants without malformations born in Denmark from January 1, 2012, to December 31, 2018. UC-pH levels were categorized as less than 7.00, 7.00 to 7.09, 7.10 to 7.19, and 7.20 to 7.50 as the reference group. The primary outcome was a composite measure of severe adverse neonatal outcomes, directly related to neonatal death, therapeutic hypothermia, mechanical ventilation, inhaled nitric oxide treatment, and seizures. All secondary outcomes measured included Apgar score, respiratory complications, and hypoglycemia. Adjusted risk ratios and 95% confidence intervals were computed from these data.

Key Findings

• Among the 340,431 infants included, the gestational age had a mean of 39.9 weeks, a mean birth weight of 3561 grams, and 51.3% were males.

• More UC-pH levels below 7.20 are more common in infants with gestational ages of 40 and 41 weeks at 31.6%-33.6% compared to those of 39 weeks at 18.2%-20.2%. A higher prevalence was also associated with male infants, classified as UC-pH levels below 7.20, at 53.9%-55.4%, than it was.

• As compared with the reference population (UC-pH 7.20 to 7.50), the severe impact of adverse outcomes was significantly greater in infants with UC-pH less than 7.00 (ARR 9.8%), between 7.00 and 7.09 (ARR 0.8%), and between 7.10 and 7.19 (ARR 0.4%). The risk for neonatal death was found to be increased only for those UC-pH levels less than 7.10.

• Hypoglycemia was defined in 21.5% of the infants with UC-pH levels below 7.10; also, it was related with a minor increment in the needed CPAP in infants that reached levels below 7.20.

• The findings challenge the traditional severe acidosis cut-off of UC-pH 7.00; they show that adverse outcomes are found in a dose-dependent manner, with an increasing frequency at higher pH levels. This would infer that the threshold for more frequent observation and intervention should now be reappraised in clinical practice.

This large-scale study now provides strong evidence for the fact that neonatal risks are not restricted to UC-pH levels below 7.00. Hypoglycemia, respiratory complications, and need for therapeutic interventions were some poor outcomes at UC-pH levels within the range of 7.00-7.19. The consideration of gestational age and sex differences in UC-pH is very important since they were correlated with different degrees of acidosis, something this study has pointed out. In addition, the generalizability is further strengthened by the large and unselected population. The observational nature of the study means further studies are needed to establish causality and further specify guidelines for the clinical management of UC-pH.

This study, in other words, outlines that UC-pH values above the threshold value of severe acidosis of 7.00 are related to poor neonatal outcome. Therefore, the results may suggest revision in current clinical practice regarding neonatal monitoring and intervention threshold based on UC-pH. In identification of this prominent risk above the level of UC-pH 7.00, changes in clinical protocols might help improve neonatal care and lower the incidence of unwanted neonatal outcomes.

Reference:

Andersson, C. B., Klingenberg, C., Thellesen, L., Johnsen, S. P., Kesmodel, U. S., & Petersen, J. P. (2024). Umbilical cord pH levels and neonatal morbidity and mortality. JAMA Network Open, 7(8), e2427604. https://doi.org/10.1001/jamanetworkopen.2024.27604