Technical progress in fetal electrocardiography--a review

The fetal electrocardiogram (FECG) was first demonstrated 80 years ago, but initial progress in research into the subject was slow and limited by the technical equipment available. As improved amplifiers became available, the detection of the waveform became easier, but observation of waveform morphology was still difficult because of background noise. The signal-to-noise ratio of the original FECG waveform was improved considerably with the use of directly applied fetal electrodes, and the development of digital computer techniques has allowed signal enhancement. It is now possible to monitor the FECG waveform continuously in labor and reliably produce waveforms with all of the components clearly defined.