Abstract

Background: Knowledge of fetal oxygen saturation, as an adjunct to electronic fetal monitoring, may be associated with a significant change in the rate of cesarean deliveries or the infant's condition at birth. Methods: We randomly assigned 5341 nulliparous women who were at term and in early labor to either «open» or «masked» fetal pulse oximetry. In the open group, fetal oxygen saturation values were displayed to the clinician. In the masked group, the fetal oxygen sensor was inserted and the values were recorded by computer, but the data were hidden. Labor complicated by a nonreassuring fetal heart rate before randomization was documented for subsequent analysis. Results: There was no significant difference in the overall rates of cesarean delivery between the open and masked groups (26.3% and 27.5%, respectively; p = 0.31). The rates of cesarean delivery associated with the separate indications of a nonreassuring fetal heart rate (7.1% and 7.9%, respectively; p = 0.30) and dystocia (18.6% and 19.2%, respectively; p = 0.59) were similar between the two groups. Similar findings were observed in the subgroup of 2168 women in whom a nonreassuring fetal heart rate was detected before randomization. The condition of the infants at birth did not differ significantly between the two groups. Conclusions: Knowledge of the fetal oxygen saturation is not associated with a reduction in the rate of cesarean delivery or with improvement in the condition of the newborn.