A novel modality for intrapartum fetal heart rate monitoring

Background: Intrapartum fetal heart rate (FHR) monitoring is well recommended during labor to assess fetal wellbeing. Though commonly used, the external Doppler and fetal scalp electrode monitor have significant shortcomings. Lately, non-invasive technologies were developed as possible alternatives.

Objective: The objective of this study is to compare the accuracy of FHR trace using novel Electronic Uterine Monitoring (EUM) to that of external Doppler and fetal scalp electrode monitor.

Material and methods: A comparative study conducted in a single tertiary medical center. Intrapartum FHR trace was recorded simultaneously using three different methods: internal fetal scalp electrode, external Doppler, and EUM. The latter, a multichannel electromyogram (EMG) device acquires a uterine signal and maternal and fetal electrocardiograms. FHR traces obtained from all devices during the first and second stages of labor were analyzed. Positive percent of agreement (PPA) and accuracy (by measuring root means square error between observed and predicted values) of EUM and external Doppler were both compared to internal scalp electrode monitoring. A Bland-Altman agreement plot was used to compare the differences in FHR trace between all modalities. For momentary recordings of fetal heart rate <110 bpm or >160 bpm level of agreement, sensitivity, and specificity were also evaluated.

Results: Overall, 712,800 FHR momentary recordings were obtained from 33 parturients. Although both EUM and external Doppler highly correlated with internal scalp electrode monitoring (r² = 0.98, p < .001 for both methods), the accuracy of EUM was significantly higher than external Doppler (99.0% versus 96.6%, p < .001). In addition, for fetal heart rate <110 bpm or >160 bpm, the PPA, sensitivity, and specificity of EUM as compared with internal fetal scalp electrode, were significantly greater than those of external Doppler (p < .001).

Conclusion: Intrapartum FHR using EUM is both valid and accurate, yielding higher correlations with internal scalp electrode monitoring than external Doppler. As such, it may provide a good framework for non-invasive evaluation of intrapartum FHR.