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Original Investigation
July 23, 2018

Effect of Oxygen vs Room Air on Intrauterine Fetal ResuscitationA Randomized Noninferiority Clinical Trial

Author Affiliations
  • 1Department of Obstetrics and Gynecology, Washington University School of Medicine in St Louis, St Louis, Missouri
  • 2Department of Obstetrics and Gynecology, Carolinas Medical Center, Charlotte, North Carolina
JAMA Pediatr. Published online July 23, 2018. doi:10.1001/jamapediatrics.2018.1208
Key Points

Question  Is room air comparable with maternal oxygen supplementation for intrauterine fetal resuscitation in labor?

Findings  In this randomized noninferiority trial of 114 pregnant patients with category II fetal heart tracings in labor, room air was noninferior to oxygen for the reduction of umbilical artery lactate, a cord gas marker of metabolic acidosis. There were no differences in mode of delivery or other cord gases between groups.

Meaning  Room air may be an acceptable alternative to oxygen for category II fetal heart tracings in labor.


Importance  Two-thirds of women in labor receive supplemental oxygen to reverse perceived fetal hypoxemia and prevent acidemia. Oxygen is routinely administered for category II fetal heart tracings, a class of fetal tracing used to designate intermediate risk for acidemia. This liberal use of oxygen may not be beneficial, particularly because neonatal hyperoxygenation is harmful.

Objective  To test the hypothesis that room air is noninferior to oxygen in improving fetal metabolic status among patients with category II fetal heart tracings.

Design, Setting, and Participants  This was a randomized, unblinded noninferiority clinical trial conducted between June 2016 and July 2017 in the labor and delivery ward of a single tertiary care center. Women with singleton pregnancies at 37 weeks’ gestational age or more who were admitted for delivery were eligible. Of those who met inclusion criteria, the patients who developed category II tracings in labor that necessitated intrauterine resuscitation were randomized in a 1:1 ratio to room air or oxygen. Analyses were intention-to-treat.

Interventions  The oxygen group received 10 L of oxygen per minute by nonrebreather facemask until delivery. The room air group was exposed to room air only without a facemask.

Main Outcomes and Measures  The primary outcome was umbilical artery lactate, a marker of metabolic acidosis and neonatal morbidity. Noninferiority was defined as a mean difference between groups of less than 9.0 mg/dL (1.0 mmol/L). Secondary outcomes were other umbilical artery gases, cesarean delivery for nonreassuring fetal status, and operative vaginal delivery.

Results  Of the 705 patients who met inclusion criteria, 277 (39.3%) were enrolled on admission. During labor, 114 patients (41.2% of the enrolled patients) developed category II tracings and were randomized to room air (57 patients; 50.0% of the randomized patients) or oxygen (57 patients; 50.0% of the randomized patients). A total of 99 patients (86.8% of the randomized patients) with paired cord gases were included in the modified intention-to-treat analysis. The 99 patients included 76 African American women (77%); mean (SD) age was 27.3 (6.3) years in the oxygen group and 27.8 (5.3) years in the room air group. There was no difference in umbilical artery lactate between the group on oxygen and the group on room air (mean, 30.6 mg/dL [95% CI, 27.0 to 34.2 mg/dL] vs 31.5 mg/dL [95% CI, 27.9 to 36.0 mg/dL]); P = .69). The mean difference in lactate was 0.9 mg/dL (95% CI, −4.5 to 6.3 mg/dL), which was within the noninferiority margin. There was no difference in other umbilical artery gas components or mode of delivery between groups.

Conclusions and Relevance  Among patients with category II fetal heart tracings, intrauterine resuscitation with room air is noninferior to oxygen in improving umbilical artery lactate. The results of this trial challenge the efficacy of a ubiquitous obstetric practice and suggest that room air may be an acceptable alternative.

Trial Registration  ClinicalTrials.gov Identifier: NCT02741284