Measurement of transcutaneous pCO2 and pO2 in the fetus during labor.

We used newly developed transcutaneous electrodes to measure continuously the partial pressure of oxygen (tcpO2) and carbon dioxide (tcpCO2) in 34 fetuses during labor, having simultaneous cardiotocography (CTG) and temperature measurements. We observed that tcpO2 and tcpCO2 varied with contractions during the first and second stages of labor. In some cases changes in the transcutaneous values corresponded well with changes in the CTG, we also detected changes in the fetal gas metabolism that were not noticeable on the cardiotocographic tracing. We defined the characteristic of the tcpO2 and tcpCO2 during the second stage of labor and found that the tcpO2 decreased and the tcpCO2 rose at this time.