The influence of signal loss on the comparison between computer analyses of the fetal heart rate in labour using pulsed Doppler ultrasound (with autocorrelation) and simultaneous scalp electrocardiogram.

A comparison between the computer analyses of records of the fetal heart rate (FHR) obtained simultaneously by pulsed doppler ultrasound with autocorrelation and by fetal scalp electrocardiogram (ECG) in labour showed no statistical differences when signal loss was less than 2%. Increasing signal loss, due to maternal movement, correlated significantly with greater differences between ultrasound and ECG values for mean FHR variation (r = 0.58, p less than 0.005). With higher signal loss (average 15.6%) the mean FHR variation measured by ultrasound was significantly lower than that measured by ECG (T = 3.83, p less than 0.005) but this reduction was not of clinical significance.