A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of nonreassuring fetal heart rate patterns

OBJECTIVE: Recent developments permit the use of pulse oximetry to evaluate fetal oxygenation in labor. We tested the hypothesis that the addition of fetal pulse oximetry in the evaluation of abnormal fetal heart rate pattern s in labor improves the accuracy of fetal assessment and allows safe reduct ion of cesarean deliveries performed because of nonreassuring fetal status. STUDY DESIGN: A randomized, controlled trial was conducted concurrently in 9 centers. The patients had term pregnancies and were in active labor when abnormal fetal heart rate patterns developed. The patients were randomized to electronic fetal heart rate monitoring alone (control group) or to the c ombination of electronic fetal monitoring and continuous fetal pulse oximet ry (study group). The primary outcome was a reduction in cesarean deliverie s for nonreassuring fetal status as a measure of improved accuracy of asses sment of fetal oxygenation. RESULTS: A total of 1010 patients were randomized, 502 to the control group and 508 to the study group. There was a reduction of >50% in the number of cesarean deliveries performed because of nonreassuring fetal status in the study group (study, 4.5%; vs control, 10.2%; P=.007). However, there was n o net difference in overall cesarean delivery rates (study, n = 147 [29%]; vs control, 130 [26%]; P = .49) because of an increase in cesarean deliveri es performed because of dystocia in the study group. In a blinded partogram analysis 89% of the study patients and 91% of the control patients who had a cesarean delivery because of dystocia met defined criteria for actual dy stocia. There was no difference between the 2 groups in adverse maternal or neonatal outcomes. In terms of the operative intervention for nonreassurin g fetal status, there was an improvement in both the sensitivity and the sp ecificity for the study group compared with the control group for the end p oints of metabolic acidosis and need for resuscitation. CONCLUSION: The study confirmed its primary hypothesis of a safe reduction in cesarean deliveries performed because of nonreassuring fetal status. How ever, the addition of fetal pulse oximetry did not result in an overall red uction in cesarean deliveries. The increase in cesarean deliveries because of dystocia in the study group did appear to result from a well-documented arrest of labor. Fetal pulse oximetry improved the obstetrician's ability t o more appropriately intervene by cesarean or operative vaginal delivery fo r fetuses who were actually depressed and acidotic. The unexpected increase in operative delivery for dystocia in the study group is of concern and re mains to be explained.