FETAL TRANSCUTANEOUS PCO2 MEASUREMENTS DURING LABOR

The departments of Obstetrics and Gynaecology of the Universities of Bonn and Copenhagen and the Free University of Amsterdam cooperated in the European Community Concerted Action Project 'New methods for Perinatal Surveillance'. In 95 patients fetal transcutaneous Pco(2) (tcPco(2)) recording (measuring temperature 41 degrees C) during labour was evaluated regarding its clinical applicability. During the first stage of labour fetal tcPco(2) was rather stable at a level of 7.3 +/- 1.4 kPa. In the second stage there were marked differences between the three subpopulations. In the first stage of labour the correlation between tcPco(2) and Pco(2) in fetal blood samples was 0.38 (P=0.02) and in the second stage -0.20 (P=0.36). The correlation of fetal tcPc(o)2 with umbilical artery Pco(2) was 0.30 (P=0.01) and with pH-0.30 (P=0.01). Using a fetal tcPco(2) level of 8.0 kPa as a cut-off point to predict an umbilical artery ph less then 7.20, sensitivity was 88%, specificity 65%, positive predictive value 29% and negative predictive value 97%. The likelihood ratio of a positive test was 2.47 and of a negative test 0.13. It is concluded that fetal tcPco(2) possibly can be an additional tool to exclude fetal acidosis. In case of values above 8.0 kPa further evaluation of the fetal acid-base balance is indicated.