Evaluation of an external fetal electrocardiogram monitoring system: a randomized controlled trial

Abstract

Objective: The objective of the study was to compare interpretability of 2 intrapartum abdominal fetal heart rate-monitoring strategies. We hypothesized that an external fetal electrocardiography monitoring system, a newer technology using wireless abdominal pads, would generate more interpretable fetal heart rate data compared with standard external Doppler fetal heart rate monitoring (standard external monitoring).

Study design: We conducted a randomized controlled trial at 4 Utah hospitals. Patients were enrolled at labor admission and randomized in blocks based on body mass index to fetal electrocardiography or standard external monitoring. Two reviewers, blinded to study allocation, reviewed each fetal heart rate tracing. The primary outcome was the percentage of interpretable minutes of fetal heart rate tracing. An interpretable minute was defined as >25% fetal heart rate data present and no more than 25% continuous missing fetal heart rate data or artifact present. Secondary outcomes included the percentage of interpretable minutes of fetal heart rate tracing obtained while on study device only, the number of device adjustments required intrapartum, clinical outcomes, and patient/provider device satisfaction. We determined that 100 patients per arm (200 total) would be needed to detect a 5% difference in interpretability with 95% power.

Results: A total of 218 women were randomized, 108 to fetal electrocardiography and 110 to standard external monitoring. Device setup failure occurred more often in the fetal electrocardiography group (7.5% [8 of 107] vs 0% [0 of 109] for standard external monitoring). There were no differences in the percentage of interpretable tracing between the 2 groups. However, fetal electrocardiography produced more interpretable fetal heart rate tracing in subjects with a body mass index ≥30 kg/m2. When considering the percentage of interpretable minutes of fetal heart rate tracing while on study device only, fetal electrocardiography outperformed standard external monitoring for all subjects, regardless of maternal body mass index. Maternal demographics and clinical outcomes were similar between arms. In the fetal electrocardiography group, more device changes occurred compared with standard external monitoring (51% vs 39%), but there were fewer nursing device adjustments (2.9 vs 6.2 mean adjustments intrapartum, P < .01). There were no differences in physician device satisfaction scores between groups, but fetal electrocardiography generated higher patient satisfaction scores.

Conclusion: Fetal electrocardiography performed similarly to standard external monitoring when considering percentage of interpretable tracing generated in labor. Furthermore, patients reported overall greater satisfaction with fetal electrocardiography in labor. Fetal electrocardiography may be particularly useful in patients with a body mass index ≥30 kg/m2.

Keywords: external monitoring; fetal electrocardiogram; fetal electrocardiography; fetal heart rate monitoring; intrapartum fetal monitoring; labor monitoring.

Conflict of interest statement

Conflict of Interes

Authors report no conflict of interest.

Copyright © 2020 Elsevier Inc. All rights reserved.

Figures

Figure 1.. Randomization and Flow of Participants Through the Trial

This figure demonstrates a flow diagram of study participant enrollment, randomization and participation during the study period. Abbreviations: ECG, electrocardiogram; SEM, standard electronic monitoring; BMI, body mass index.

Figure 2.. Comparison of device adjustments required intrapartum

Mean number of device adjustments for all subjects as well as subjects stratified by BMI are shown. Asterisk indicates significant difference between study groups (P value

Figure 3.. Patient Device Satisfaction Survey

Comparison of patient satisfaction scores on assigned study device is shown, where bars oriented to the right indicate a favorable satisfaction score. Neutral and negative responses are indicated with bars oriented to the left. Survey gauged patient satisfaction with respect to skin “Irritation” on assigned device, overall device “Comfort,” ease of “Walking,” Re-“Positioning” in labor as well as whether the patient would be likely to “Recommend” the device to others in the future. Asterisk indicates significant difference between study groups. (P value