The accuracy of abdominal ECG for fetal electronic monitoring.

The aim of this study was to investigate the quality of the abdominal fetal electrocardiography (aFECG), and compare the short term and long term variability registered by this method with the direct fetal electrocardiography (dFECG). With three cardiotocographs the aFECG, the dFECG and the maternal ECG were registered simultaneously and stored on a magnetic tape. After analogue-digital conversion, the information was calculated in a computer system. The variability registered by aFECG and dFECG was compared allowing a difference of both one beat and two beats/min. From nine patients in early labour 30651 heart beats were registered by dFECG. By aFECg 27720 beats were registered. Within a window of +/- 10 ms 98.5% of all pulses registered by aFECG were found. The correlation coefficients for short term variability were 0.75 and 0.91. For long term variability the correlation coefficients were 0.94 and 0.98. To allow calculations of the short term variability the registration of the instantaneous fetal heart rate is necessary. In the antenatal period only indirect methods for electrocardiography are possible. The present report shows that with the abdominal electrocardiography the short term and long term variability can be judged. the quality of the registrations is good enough to allow computer calculations of the information.