Intrapartum signal quality with external fetal heart rate monitoring – A two way trial of external Doppler CTG ultrasound and the abdominal fetal electrocardiogram

Objective: The objective of this study was to assess the fetal heart rate (FHR) signal quality of non-invasive abdominal fetal ECG in comparison to Doppler ultrasound CTG during the first and second stage of labour.

Study design: This was a prospective observational study of non-invasive fetal ECG using 5 abdominally sited electrodes against the traditional Doppler ultrasound CTG probe on 144 patients. Data were analyzed for signal quality before and after outlier removal.

Results: Abdominal fetal ECG signal quality was significantly better during the first stage of labour in comparison to Doppler CTG (median fetal ECG reliability of 95.7% versus median 87.3% for Doppler, p < 0.001), whereas during second stage of labour equivalence was demonstrated (p>0.05). For the first and second stage of labour fetal ECG showed 106 /135 (78.5%) and 46 / 98 (46.9%) women having fetal signal loss below 20%, respectively. Similarly Doppler ultrasound CTG demonstrated 104 / 135 (77.0%) and 51 / 98 (52.0%) women having fetal signal loss below 20% during first and second stage of labour respectively.

Conclusion: The non-invasive abdominal fetal ECG presents an improved FHR signal quality during the first stage of labour and an equivalent signal quality during the second stage.

Doppler ultrasound cardiotocogram (CTG) - non-invasive fetal electrocardiogram (fECG) - fetal heart rate (FHR) - first and second stage of labour - signal quality