Continuous acid-base assessment of the human fetus during labour by tissue pH and transcutaneous carbon dioxide monitoring

Summary. Simultaneous monitoring of fetal tissue pH (t-pH) and transcutaneous carbon dioxide (Tc- P co₂) was performed in 30 labours. Both t-pH and Te- P co_-2 at delivery were positively correlated with pH ( r = 0·69) and P co₂( r = 0·68) of the umbilical artery blood. A tissue/transcutaneous standard base excess (t-SBE) was derived from the t-pH and the Tc- P co₂ and calculated for 13 fetuses a t delivery; there was a correlation with standard base excess of umbilical artery blood. An analysis of t-pH and Tc- P co₂ changes during the last hour of labour revealed that only infants who were born with decreased pH of the umbilical artery blood had decreasing t-SBE, while all others had a constant t-SBE.