Normal range of fetal transcutaneous carbon dioxide tension during labour.

Fetal transcutaneous carbon dioxide tension (tc-PCO2) was monitored during 122 deliveries, using an electrode temperature of 44 degrees C in 80 cases and of 41 degrees C in 42 cases. Significant correlations between tc-PCO2 and umbilical artery blood PCO2 were found using both electrode temperatures, but the regression lines indicated a larger and more inconstant CO2-contribution from skin metabolism when the low electrode temperature was used. Normal range of tc-PCO2 was calculated at 41 degrees C and 44 degrees C electrode temperatures. Mean values of fetal tc-PCO2 were found to increase during normal labour, and especially in fetuses developing acidosis, but only four of six infants born with acidaemia had tc-PCO2 values exceeding the normal range.