Continuous intrauterine transcutaneous PO2(tcPO2) measurement was performed in 30 deliveries. The various characteristics of labor (peak of contractions, duration, and contraction interval) were correlated with the tcPO2integral. The best correlation was seen between the tcPO2integral and that of the contraction intervals. As the data show significant correlations with the pattern of labor, continuous tcPO2measurement is a reliable and sensitive method for recognizing PO2alterations early, especially in high-risk deliveries.