I started in labor & delivery in 1979, just at the beginning of the use of electronic fetal monitoring (EFM). To give you an idea of what that means, I was at a tertiary perinatal center where we had 3 fetal monitors and 10 labor rooms, so when I started my career as a nurse the majority of our patients were monitored by auscultation and palpation. By 1981, just 2 years later, every labor room had a fetal monitor, and they were also common at our community hospitals. The tipping point had been reached in just 2 years. And the training for every clinician included the triad of corrective measures (intrauterine resuscitation): IV fluids, position changes, and maternal oxygen supplementation. It wasn’t until 2008, when I read an article by Kathleen Rice Simpson questioning the routine use of oxygen for fetal heart rate (FHR) tracings [1], that I began to question this common practice. This article will review the history of the controversy and conclude with the current state of the science related to supplemental maternal oxygen as a corrective measure, and provide what I believe is best practice given the evidence.
While Simpson’s article in 2008 certainly began a conversation among many of us teaching EFM, it was an expert opinion piece published in 2014 by Hamel, Anderson, & Rouse that really set the stage for controversy. In that paper, published in the esteemed American Journal of Obstetrics and Gynecology (aka the grey journal) the authors made a case for the complete cessation of supplemental maternal oxygen use for FHR tracings. Their arguments were strong, pointing out the paucity of evidence for its use as well as the potential for harm from hyperoxygenation [2]. To many of us, this was heresy – calling for the end of something that had been so routine, so integrated into daily practice since the dawn of EFM. And the publication was met with some serious pushback from leaders in the field. An important factor in reviewing literature is to be sure to look for letters to the editor that follow. And for Hamel and colleagues, that was a letter from Garite, Nageotte, and Parer suggesting that while oxygen was definitely being overused, and agreeing that more research was needed, oxygen was still indicated for the more concerning FHR tracings and its use should not be abandoned wholesale [3]. These sentiments were echoed by others as well [4] [5]. Hamel and colleagues’ responses made it clear that they were standing their ground for discontinuing oxygen use as a corrective measure except in cases of maternal hypoxia until there was clear evidence for the practice [6] [7].
And from controversy came the science. While a 2012 Cochrane review included only 2 trials of intrapartum maternal oxygen use as a corrective measure for FHR changes, and concluded that the evidence was insufficient to draw any conclusion [8], studies published since that time seem to have answered the question, including the specific issue of oxygen use versus room-air for Category 2 tracings requiring intervention (no difference!) [9]. So let’s fast forward to 2021 and the recently published systematic review and meta-analysis. Raghuraman and colleagues looked at 16 randomized trials worldwide between 1982 and 2020, and the trials include oxygen use in scheduled cesarean delivery as well as its use in the intrapartum setting. While the studies reviewed looked at multiple outcomes, the author’s conclusion was that the evidence to date shows no improvement in umbilical artery pH or neonatal outcomes, and while there is definitely a need for further research, it is time to set aside routine use of oxygen as a corrective measure unless there is maternal hypoxia [10].
The question remains – what is best practice? In my opinion, it all starts with understanding the oxygen pathway shown here and the application of critical thinking:
Environment
Lungs
Heart
Vasculature
Uterus
Placenta
Cord
Fetus
The oxygen pathway shows the route for oxygen molecules to reach the fetus. In light of this core physiology and a review of the current evidence, supplemental maternal oxygen should be reserved for situations in which the clinician’s review of the oxygen pathway reveals a problem with maternal oxygenation (level of maternal lungs) such that maternal hypoxia must be corrected*. Clinicians should be made aware of the new evidence regarding supplemental oxygen as a corrective measure, and trained to consider all aspects of the oxygen pathway when evaluating FHR changes and considering corrective measures. There are many more corrective measures available today than the triad I was taught back in 1979, and we are so much better today at looking at the evidence for a particular intervention. Combining strong clinical knowledge of core physiology and providing clinicians with updates on current evidence can dramatically effect our outcomes. Controversy is often the starting point for what will eventually become best practice, and in the case of oxygen use, we now know that less really is more!
* For a full discussion of the oxygen pathway, fetal response, and two core principles of FHR tracing interpretation, please refer to the new 9th edition of the Mosby Pocket Guide to Fetal Monitoring.
This article was submitted by Lisa A. Miller, CNM, JD
References
[1] Simpson KR. Intrauterine resuscitation during labor: should maternal oxygen administration be a first-line measure? Semin Fetal Neonatal Med. 2008 Dec;13(6):362-7.
[2] Hamel MS, Anderson BL, Rouse DJ. Oxygen for intrauterine resuscitation: of unproved benefit and potentially harmful. Am J Obstet Gynecol. 2014 Aug;211(2):124-7.
[3] Garite TJ, Nageotte MP, Parer JT. Should we really avoid giving oxygen to mothers with concerning fetal heart rate patterns? Am J Obstet Gynecol. 2015 Apr;212(4):459-60, 459.e1.
[4] Ross MG, Amaya KE. Maternal oxygen use during labor. Am J Obstet Gynecol. 2015 Mar;212(3):410.
[5] Doyle JL, Silber AC. Maternal oxygen administration for intrauterine resuscitation. Am J Obstet Gynecol. 2015 Mar;212(3):409.
[6] Hamel MS, Hughes BL, Rouse DJ. Reply: To PMID 24412117. Am J Obstet Gynecol. 2015 Mar;212(3):410.
[7] Hamel MS, Hughes BL, Rouse DJ. Whither oxygen for intrauterine resuscitation? Am J Obstet Gynecol. 2015 Apr;212(4):461-2. 461.e1.
[8] Fawole B, Hofmeyr GJ. Maternal oxygen administration for fetal distress. Cochrane Database Syst Rev. 2012;12:CD000136.
[9] Raghuraman N, López JD, Carter EB, Stout MJ, Macones GA, Tuuli MG, Cahill AG. The effect of intrapartum oxygen supplementation on category II fetal monitoring. Am J Obstet Gynecol. 2020 Dec;223(6):905.e1-905.e7.
10. Raghuraman N, Temming LA, Doering MM, Stoll CR, Palanisamy A, Stout MJ, Colditz GA, Cahill AG, Tuuli MG. Maternal Oxygen Supplementation Compared With Room Air for Intrauterine Resuscitation: A Systematic Review and Meta-analysis. JAMA Pediatr. 2021 Apr 1;175(4):368-376.
About the author:
Founder of Perinatal Risk Management and Education Services (PRMES), Lisa Miller is a certified nurse-midwife with 40 years of clinical experience. As a midwife and a lawyer, she has a unique understanding of the impact of law on medicine and nursing. Lisa served as an Assistant Professor in Obstetrics and Gynecology at Northwestern University Medical School and is co-author of three textbooks on electronic fetal monitoring. Today, much of her time is spent teaching an evidence- and consensus-based approach to fetal monitoring based on the NICHD nomenclature, and educating physicians, midwives, and nurses on cognitive bias, medical and nursing error, as well as safety-based approaches to normalize labor. She is an active member of AWHONN and served on the board of directors from 2016-2018. In addition to her work with AWHONN, Ms. Miller is a member of ACOG and has worked with state and national ACOG memberships in fetal monitoring education.