Fetal pulse oximetry and cesarean delivery: Commentary

ABSTRACT More than 5 years ago the Food and Drug Administration approved, conditionally, the OxiFirst Fetal Oxygen Saturation Monitoring System as an adjunct to electronic fetal monitoring. The goal of monitoring was to gain more knowledge of the condition of the fetus by continuously monitoring oxygen saturation when there is a nonreassuring fetal heart rate pattern. The sensor is inserted through the dilated cervix following membrane rupture, and positioned against the fetal face. This randomized trial, conducted at 14 university-based clinical centers, was designed as a means of learning whether adjunctive fetal oximetry lessens the need for cesarean delivery. Participants were nulliparous women with a singleton fetus in cephalic presentation at 36 or more weeks' gestation. The 5341 women in the study were randomized to either “open” fetal pulse oximetry with oxygen saturation values displayed to the clinician, or “masked” oximetry in which the results were hidden. Overall rates of cesarean delivery were 26.3% for the open group and 27.5% for masked monitoring, not a significant difference. The respective operative delivery rates were 7.1% and 7.9% for a nonreassuring fetal heart rate pattern; and 18.6% and 19.2% for dystocia, Findings were similar for the 2168 women in whom a nonreassuring fetal heart rate pattern was identified before randomization. There were no significant differences between the open and masked groups in the rates of forceps or vacuum-assisted delivery, even after excluding women who had labor induced. The relative risk of cesarean delivery associated with knowing the fetal oxygen saturation was 0.96 (95% confidence interval, 0.87–1.04). Neither maternal nor infant complications differed significantly in incidence between the study groups. The sensitivity, specificity, positive predictive value, and negative predictive value of a nonreassuring fetal heart rate pattern for low oxygen saturation (defined as less than 30% for 2 consecutive minutes) were, respectively, 87%, 19.5%, 35%, and 75%. One-fourth of fetuses with a normal heart rate pattern exhibited low oxygen saturation. This large-scale study failed to demonstrate that knowledge of intrapartum fetal oxygen saturation significantly lowers the rate of cesarean delivery or improves infant outcomes. The findings emphasize the need to rigorously evaluate new technologies.