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 a dministration on fetal arterial oxygen saturation in normal human fetu ses during labor. STUDY DESIGN: Twenty healthy women with uncomplicate d pregnancies were studied during active labor at term. Arterial oxyge n 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 o f prolonged (45 minutes) supplemental 40% oxygen administration were e valuated. Differences between groups were analyzed by analysis of vari ance; 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 minut es 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 satura tion determined by reflectance pulse oximetry in normal fetuses. Becau se the administration of oxygen by standard mask techniques rarely res ults in 40% inspired oxygen concentration, fetal benefits of such intr apartum maternal oxygen administration are questionable.