Oxygen for Category II Intrauterine Fetal Resuscitation: A Randomized, Noninferiority Trial

Maternal oxygen administration for concerning fetal heart rate tracing (FHT) patterns is common practice on Labor and Delivery units in the United States. Despite the broad use of oxygen, it is unclear if this practice is beneficial for the fetus. Category II FHT, as defined by the National Institute of Child Health and Human Development (NICHD) (Robinson), is a broad class of FHT patterns that may suggest cord compression and/or placental insufficiency for which oxygen is most commonly administered. Although some animal and human studies (Khazin, Althabe) have demonstrated that maternal hyperoxygenation can alleviate such fetal heart rate decelerations, this purported benefit has not been shown to translate into improved fetal outcomes, particularly in relation to acid-base status. In fact, some studies suggest harm with oxygen use due to lower umbilical artery pH and increased delivery room resuscitation (Nesterenko, Thorp) or increased free radical activity (Khaw). Given the indeterminate evidence for this ubiquitously employed resuscitation technique, there is an urgent need to further study the utility of maternal oxygen administration in labor for fetal benefit.

We propose a randomized controlled non-inferiority trial comparing oxygen to room air in patients with Category II FHT. Our central hypothesis is that room air alone is not inferior to oxygen administration with regard to neonatal acid-base status and FHT and may in fact, be a safer option for resuscitation due to less production of reactive oxygen species.

Primary Aim: Determine the effect of maternal oxygen administration for Category II FHT on arterial umbilical cord lactate.

Hypothesis: Room air, as a substitute for oxygen supplementation, is no different than oxygen in altering the acid-base status of the neonate as reflected in umbilical arterial (UA) lactate.

Fetal hypo-oxygenation, as reflected by decelerations in the FHT, results in metabolic acidosis due to a shift from aerobic to anaerobic metabolism in which lactate and hydrogen ion production significantly increase causing a decrease in pH (Tuuli). Elevated umbilical cord lactate has been shown to be a surrogate for fetal metabolic acidosis and resultant neonatal morbidity (Tuuli, Westgren). The theorized benefit of maternal oxygen administration is increased oxygen delivery to the fetus resulting in reversal of anaerobic metabolism/ metabolic acidosis. This, however, has not been substantiated by evidence thus far. Women with persistent Category II FHT tracing will be randomly assigned to supplemental oxygen or room air. The primary outcome will be umbilical arterial lactate level, and secondary outcomes will be other umbilical cord gas parameters including UA pH, UV oxygen saturation, and UA base deficit.