Noninvasive Recording of True-to-Form Fetal ECG during the Third Trimester of Pregnancy

Figure 3

(a) Transabdominal record at the 34th week of pregnancy. Contrary to previous recordings, fetal signals are so small in this case that they cannot be identified. (b) The software automatically identifies the maternal ECG R waves. (c) The system calculates the average of 30 maternal cardiac cycles, and then the computer extracts in real time the averaged signal from each identified maternal ECG heart event. (d) The “cleaned” abdominal signal, maternal waves are removed. (e) The preprocessed sound signals of the cardiotocograph can be used to identify fetal cardiac events. (f) The hardware generates automatically trigger signs from the acoustic waves. (g) The identified fetal signals are averaged (in this case 76 fetal heart events are averaged). (h) The final result is an approximately true-to-form fetal ECG. It is important to emphasize that in the example shown above the fetal ECGs amplitude is less than 10 μV.