Transcutaneous carbon dioxide measurements in the fetus during labor.

Transcutaneous partial pressure of carbon dioxide (transcutaneous PCO2) was measured in 55 fetuses during labor with a carbon dioxide electrode applied to the fetal scalp by a suction ring. The application procedure was simple and reliable, with reapplication required only 0.6 times per patient. The transcutaneous PCO2 recordings were of good quality and were correlated to carbon dioxide tensions in the umbilical artery (r = 0.60, p less than 0.001) and vein (r = 0.69, p less than 0.001) as well as to capillary PCO2 obtained by fetal scalp blood sampling (r = 0.96, p less than 0.001). If fetal distress occurred, transcutaneous PCO2 was significantly higher than in the uncompromised fetus. Although transcutaneous PCO2 monitoring might be useful for surveillance of the fetus during labor, it must still be reserved for scientific purposes for the time being.