Detection of fetal movement using Doppler ultrasound.

Using conventional cardiotocographic equipment with the ultrasound transducer placed to detect the fetal heart, we obtained unprocessed Doppler signals in the frequency range 13-70 Hz and used them to detect movements of the fetal trunk. In an assessment of maternal perception of fetal activity, we found that Doppler signals were associated with 739 of 780 appreciated movements (95%); however, 36% of all the Doppler signals were unaccounted for. A separate comparison of the Doppler signals against real-time ultrasound observations of fetal activity showed that 913 of 970 visualized trunk movements (94%) were associated with Doppler signals. Other Doppler signals were found to be due principally to fetal breathing and fetal hiccups. Appropriate processing of the Doppler signals obtained during antenatal cardiotocography may allow an objective assessment of fetal activity to be added to the fetal heart rate recording.