Multicenter study on the clinical value of fetal pulse oximetry .2. Compared predictive values of pulse oximetry and fetal blood analysis

OBJECTIVE: Our purpose was to compare the predictive value of intrapartum fetal pulse oximetry with that of fetal blood analysis for an abnormal neonatal outcome in case of an abnormal fetal heart rate. STUDY DESIGN: A prospective multicenter observational study was conducted from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded with a Nellcor N-400 fetal pulse oximeter in case of an abnormal fetal heart rate during labor. Simultaneous readings of fetal oxygen saturation and fetal blood analysis obtained before birth (i.e., either al full dilatation or before cesarean section when indicated) were compared with the neonatal status. The criteria for an abnormal neonatal outcome were (1) an umbilical arterial blood pH less than or equal to 7.15 and (2) a combined Variable including 5-minute Apgar score less than or equal to 7, umbilical arterial pH less than or equal to 7.15, secondary respiratory distress, transfer in a neonatal care unit, or neonatal death. RESULTS: At a 7.20 threshold for fetal scalp pH and 30% for fetal oxygen saturation (i.e., the 10th percentile in the study population), the predictive Value of fetal pulse oximetry was similar to that of fetal blood analysis for an arterial umbilical pH less than or equal to 7.15 and for an abnormal neonatal outcome (positive predictive value 56% vs 55%, negative predictive value 81% vs 82%, sensitivity 29% vs 35%, and specificity 93% vs 91%, respectively). The receiver-operator characteristic curve showed similar performance of either technique for cutoff values less than or equal to 7.20 for fetal blood pH and less than or equal to 30% for fetal oxygen saturation, whereas fetal pulse oximetry became superior at higher thresholds. CONCLUSION: The predictive Value of intrapartum fetal pulse oximetry can be favorably compared with that of fetal blood analysis. Randomized controlled management trials can now be performed to assess potential clinical benefits of this new tool.