Fetal ECG waveform analysis during labour

The fetal electrocardiographic waveform (ECG) may be obtained in labour from the same scalp electrode used in the detection of fetal heart rate. Some features of the waveform, in addition to fetal heart rate, may have clinical significance. The relationship between the PR and RR intervals has been shown to be normally positively correlated but becomes negative during decelerations associated with increasing acidosis in clinical studies. The QRS complex width has been shown to be related to cardiac size with increasing gestational age or cardiac failure. Most information is available on the ST waveform of the fetal ECG. Changes in this waveform occuring during hypoxia have been extensively studied in animal preparations and in human observational studies. The results have suggested that the addition of ST waveform analysis to the cardiotocogram (CTG) might improve the predictive value of intrapartum monitoring. The results of a clinical trial are reported which confirm this improvement