FETAL ELECTROMECHANICAL INTERVALS IN LABOUR

Summary

Measurements of fetal cardiac electromechanical intervals were obtained in two groups of patients before and during labour. This was achieved by means of a system, developed in our Department, which allows the simultaneous recording of the fetal electrocardiogram and filtered Doppler signals from the fetal heart. The intervals studied were the pre-ejection period (PEP), the phase of isovolumetric contraction (IVC) and the left ventricular ejection time (LVET). Mean and SD values prior to the onset of labour were established and found to be 73.6±4.7 mseconds, 38.9±5.8 mseconds, and 155.2±9.6 mseconds respectively. While LVET varied inversely with heart rate, PEP and IVC showed no such correlation. In the second part of the study, serial measurements were made throughout labour in 22 patients. Eighteen of these fetuses had normal pH values at or near delivery, and in 16 of them PEP measurements varied by less than 10 mseconds from the pre-labour value, the remaining two fetuses exhibiting an unexplained shortening of this interval. All four fetuses with evidence of acidosis at delivery had PEP measurements which lengthened by more than 10 mseconds during labour. It is suggested that, with further development and experience, this technique may prove to be a useful adjunct to current methods for intrapartum fetal monitoring.