Peripartum maternal oxygen supplementation does not yield a clinically relevant improvement in umbilical artery gas pH or other neonatal outcomes, reported Nandini Raghuraman, MD, MS, of the Washington University School of Medicine, St. Louis, MO, and her associates.
In a meta-analysis of 16 studies identified between Feb. 18 and April 3, 2020, the investigators sought to determine whether maternal oxygen supplementation during delivery leads to improved measures in umbilical artery (UA) gas and neonatal outcomes. Using data from randomized clinical trials, they compared peripartum oxygen supplementation with room air and examined the link between oxygen delivery during regular labor or planned cesarean delivery (CD) with UA gas measures and other neonatal outcomes.
Altogether, 1,078 patients were randomized to the oxygen group or the room air group. UA pH remained similar between the two groups even after the researchers factored in risk of bias, use of low-flow devices, or FIO2 below 60%, noted the authors. Oxygen supplementation also appeared to reduce rates of UA pH that were less than 7.2 and increase UA PaO2 relative to room air during scheduled cesarean deliveries, they added.
Considerable interstudy heterogeneity was found
Although marginally lower one-minute Apgar scores were observed in infants whose mothers received oxygen during cesarean delivery, the mean difference between oxygen and room air was less than a point and there were no other statistically significant differences in any secondary outcomes, the authors said. Considerable interstudy heterogeneity was noted across most of the study outcomes.
It is important to note that results pooled from all the studies reviewed indicated an increase in UA PaO2 but no notable differences in UA pH when oxygen was used. Citing multiple studies included in the review, the authors observed that UA PaO2 is a “poor estimator of neonatal morbidity” because, when evaluated in cord blood gas, it represents dissolved oxygen and is not an accurate indication of how much oxygen is bound to hemoglobin. For this reason, dissolved oxygen content by itself is not an indication of hypoxia or subpar tissue oxygenation.
“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. An intervention that increases the PaO2 without concomitantly increasing the pH has limited clinical benefit, particularly because hyperoxemia is associated with production of free radicals and oxidative cell damage in adults and neonates,” they explained.
With unproven benefits and potential for risk of harm, prolonged oxygen use should be 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,” the authors suggested. For the time being, they cautioned limiting prolonged oxygen use since the benefits are unproven and there is a potential risk of harm.
In a separate interview, Iris Krishna, MD, MPH, FACOG, Emory University, Atlanta, noted, “The use of maternal supplemental oxygen with the intent of improving fetal oxygenation is a common clinical practice. Previous studies on maternal oxygen supplementation during labor have yielded conflicting results; however, there is growing literature suggesting that maternal intrapartum supplemental oxygenation may not provide clinically significant benefit and there may even be potential harm to mother and baby.
“Unique to this meta-analysis is evaluation of maternal oxygen supplementation in the presence or absence of labor, hypothesizing that placental oxygen transfer may be affected by regular uterine contractions. The pooled results suggest that the use of maternal supplemental oxygenation does not result in clinically relevant fetal oxygenation in the presence or absence of labor when compared to room air. A limitation of this meta-analysis is that the use of oxygen in response to nonreassuring fetal tracing was not assessed, the most common clinical indication for maternal oxygen supplementation.
“This study further challenges the practice of maternal intrapartum supplemental oxygen and highlights that we have much to learn about the impact of this practice. More research is needed to assess optimal duration of oxygen supplementation, safety and efficacy of oxygen supplementation, appropriate clinical indications for oxygen supplementation, as well as the long-term neonatal outcomes of in utero hyperoxygenation.“
Dr. Raghuraman reported receiving multiple grants and acknowledged multiple funding sources. Her colleagues and Dr. Krishna had no conflicts of interest to report.