Fetal electrocardiogram changes in relation to fetal heart rate patterns during labor.

Abstract The fetal electrocardiograms (FECG's) obtained from Hon's electrodes were analyzed and averaged in 234 labors in order to investigate whether FECG configuration changes occurred during fetal heart rate (FHR) periodic changes. During severe variable decelerations modifications of the P wave and of the PQ interval were constantly noted (biphasic or absent P wave, shortened PQ interval); modifications of the ventricular repolarization appeared in four cases out of 26. During late decelerations changes of the P wave and of the PQ interval appeared constantly (prolonged or shortened PQ interval, biphasic or absent P wave) and were dependent on the amplitude of the FHR drop. Changes of the ST segment and/or T wave were repeatedly observed in 17 out of 35 cases; no definite relationship was found between the onset of these changes and the fetal scalp pH values. Analysis of the FECG configuration helps to elucidate the pathophysiologic mechanisms involved in FHR changes and in some instances allows a more precise evaluation of the fetal state from a clinical standpoint.