Abstract: Objective To study the oxygenation and acid-base balance in fetus for prediction of fetal distress by monitoring the incidence rate of fetal oxygen saturation（FSaO2）during intrapartum. Methods External electronic FSaO2 monitoring was performed during the active phases of the first and second labor stages in 62 parturients.Sensitivity,specificity,positive and negative predictive values of the monitoring methods were determined based on the Apgar score and cord artery blood gases. Results The mean FSaO 2 was significantly higher during the active phase of the first stage than during the active phase of the second stage.FSaO2 was significantly correlated with pH,PO2,PCO2 and base excess（BE）of the cord blood.The diagnostic sensitivity,specificity,positive and negative predictive value of 30%cutoff for intrauterine fetal distress were 90%,96.2%,81.8%,96.2%and 95.2%,respectively. Conclusion FSaO 2 monitoring is an effective method for the diagnosis of intrauterine fetal distress.