INTRAPARTUM FETAL PULSE OXIMETRY - THE EFFECTS OF MATERNAL HYPEROXIA ON FETAL ARTERIAL OXYGEN-SATURATION

OBJECTIVE: Our purpose was to observe the effects of maternal oxygen administration on fetal arterial oxygen saturation in normal human fetuses during labor. STUDY DESIGN: Twenty healthy women with uncomplicated pregnancies were studied during active labor at term. Arterial oxygen saturation was measured by a noninvasive reflectance pulse oximeter designed for fetal application (Nellcor, Inc, Pleasanton, Calif.). The first group was studied during 20-minute intervals of inspired oxygen concentrations of 21%, 40%, and 100%. In a second group the effects of prolonged (45 minutes) supplemental 40% oxygen administration were evaluated. Differences between groups were analyzed by analysis of variance; significance was considered at p < 0.05. RESULTS: A significant increase in fetal arterial oxygen saturation (50% +/- 8% vs 64% +/- 6%, p < 0.0001) was detected in the group given 100% oxygen for 20 minutes but not in the groups that received 40% oxygen for 20 or 45 minutes. CONCLUSIONS: Prolonged maternal administration of 40% oxygen resulted in no significant demonstrable change in fetal arterial oxygen saturation determined by reflectance pulse oximetry in normal fetuses. Because the administration of oxygen by standard mask techniques rarely results in 40% inspired oxygen concentration, fetal benefits of such intrapartum maternal oxygen administration are questionable.