Continuous measurement of tissue pH in the human fetal scalp.

A method for continuous measurement of scalp tissue pH is described. The tissue pH probe was found to be robust and values for tissue pH were close to those for scalp blood pH. Combining the pH and fetal heart fate (FHR) electrodes in the one mechanical assembly facilitated application to the fetal scalp in early labour but the combined assembly electrode was found to have some disadvantages and manufacture of a separate tissue PH electrode is recommended. Continuous monitoring of scalp tissue pH enables closer study of the physiological basis of changes in fetal acid base status and should prove useful to the obstetrician in management of high risk pregnancies during labour.