Objective: To compare the predictive value of intrapartum fetal pulse oximetry to that of fetal blood analysis for an abnormal neonatal outcome in case of abnormal fetal heart rate (FHR).
Study design: A prospective multicenter observational study, from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded using a Nellcor N-400 fetal pulse oximeter in case of abnormal FHR during labor. Simultaneous readings of fetal oxygen saturation and fetal blood analysis obtained before birth, i.e. either at 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 < or = 7.15 and 2) a combined variable including: 5 min. Apgar score < or = 7, umbilical arterial pH < or = 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 tenth centile in the study population), the predictive value of fetal pulse oximetry was similar to that of fetal blood analysis for an arterial umbilical pH < or = 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 operating curve showed similar performance of either technique for cut-off values < or = 7.20 for fetal blood pH and < or = 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.