Peripartum O2 Not Tied to Better Umbilical Arterial Outcomes

Maternal oxygen supplementation at the time of delivery yielded no substantial difference in umbilical artery (UA) pH compared with room air, researchers reported.

In a meta-analysis and systematic review, oxygen administration was associated with no significant difference in UA pH (weighted mean difference 0.00, 95% CI −0.01 to 0.01), according to Nandini Raghuraman, MD, MS, of Washington University School of Medicine in St Louis, and co-authors.

While oxygen use was linked with an increase in umbilical artery (UA) PaO₂ (weighted mean difference 2.57 mm Hg, 95% CI 0.80-4.34 mm Hg), the authors cautioned that heterogeneity among the studies included in their analysis was significant (I²=49.88%, P=0.03). Still, “The UA pH remained similar between the oxygen and room air groups even after accounting for risk of bias, use of low-flow devices, or FiO2 [fraction of inspired oxygen] less than 60%,” they wrote in JAMA Pediatrics.

In an editorial accompanying the study, Mohan Pammi, MD, PhD, of Baylor College of Medicine in Houston, and co-authors noted that two of three U.S. women are estimated to get “oxygen supplementation for non-reassuring fetal heart rate patterns” at one point or another over the course of labor.

They noted that the practice has been given a green light by the American College of Obstetricians and Gynecologists and the Association of Women’s Health, as well as the Obstetric and Neonatal Nurses.

However, there is no physiologic basis for this practice, Pammi’s group argued, and the current findings clearly demonstrate this. “While maternal oxygen administration to the normally oxygenated mother in labor is likely as innocuous as it is useless, concern for the practice of evidence-based medicine would seem to suggest that recommendations for its use in 2 million to 3 million women annually may be inappropriate,” they stated.

Raghuraman’s group searched for relevant data from randomized clinical trials (RCT) in Ovid MEDLINE, Embase, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials from February through April 2020, ultimately settling on 16 RCTs (n=1,078 oxygen group; n=974 room air group) and choosing a primary outcome of UA pH. “Studies were included if they were randomized clinical trials comparing oxygen with room air at the time of scheduled cesarean delivery or labor in patients with singleton, non-anomalous pregnancies. Studies that did not collect paired umbilical cord gas samples or did not report either UA pH or UA PaO2results were excluded,” they explained.

They found that, despite the potential boost in UA PaO₂, there was still no significant difference in UA base excess, UA pH less <7.2 Apgar scores, or neonatal ICU admissions. Also, UA pH values remained similar between groups after accounting for the risk of bias, type of oxygen delivery device, and fraction of inspired oxygen, the authors stated.

After stratifying by the presence or absence of labor, oxygen administration in women getting a scheduled cesarean delivery was linked with increased UA PaO₂ (weighted mean difference 2.12 mm Hg, 95% CI 0.09 to 4.15 mm Hg) and a reduction in the incidence of UA pH <7.2 (relative risk 0.63, 95% CI 0.43-0.90). However, these changes were not seen for those in labor (PaO₂ weighted mean difference, 3.60 mm Hg, 95% CI −0.30 to 7.49 mm Hg; UA pH<7.2, RR 1.34, 95% CI 0.58-3.11).

The authors noted that “Umbilical artery PaO2 has been shown to be a poor estimator of neonatal morbidity, because the PaO2 evaluated in a cord blood gas represents dissolved oxygen in the sample and does not reflect the amount of oxygen that is bound to hemoglobin.” They explained that “Prolonged tissue hypoxia leads to anaerobic metabolism, resulting in decreased pH, which is why UA pH ultimately serves as a better marker for prediction of neonatal morbidity.”

Study limitations included the possibility that the analyses were underpowered to detect differences in UA pH or other UA gas outcomes. Also, data on short- and long-term neonatal outcomes were limited.

“A large, adequately powered trial is needed to investigate the effect of maternal oxygen supplementation in response to fetal heart rate tracings on short- and long-term neonatal morbidity,” Raghuraman and co-authors stated. In the meantime, “prolonged oxygen use should be limited given lack of proven benefit and potential risk of harm,” they advised.

1. A systematic review and meta-analysis found no association between maternal oxygen supplementation and clinically relevant improvement in umbilical artery pH or other neonatal outcomes.

2. Peripartum maternal oxygen supplementation was associated with umbilical artery (UA) PaO₂ improvement but no significant difference in UA pH versus room air.

Shalmali Pal, Contributing Writer, BreakingMED™

Cat ID: 41

Topic ID: 83,41,728,791,730,41,192,925