The duration of intrapartum supplemental oxygen administration and umbilical cord oxygen content

Maternal oxygen (O2) administration is a commonly performed intrauterine resuscitation technique though to improve fetal oxygenation. However, hyperoxygenation is known to be harmful in both neonates and adults. Currently, there are no formal recommendations on whether a certain dose or duration of O2 may be most helpful in improving umbilical cord gases or neonatal outcomes. We tested the hypothesis that prolonged supplemental O2 exposure during labor is associated with increased umbilical cord O2 concentrations. This was a planned secondary analysis of a randomized noninferiority trial comparing O2 with room air in laboring patients. Patients were randomized to receive either 10 L/min O2 or room air at any point during active labor when they developed a category II fetal heart tracing that would otherwise require resuscitation. The primary outcome variable for this analysis was partial pressure of O2 in the umbilical vein. The secondary outcome variable was partial pressure of O2 in the umbilical artery. These outcome variables were compared between patients with short durations of O2 exposure and those with long durations of O2 exposure, defined as