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

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.

Effect of blood contamination on amniotic fluid detection in vitro using immunoassays.

Objective: To determine the accuracy of Actim PROM®, Amnisure®, and ROM Plus® tests for detecting amniotic fluid proteins in the setting of blood contamination.Methods: IGFBP-1 and AFP are proteins present in high concentrations in amniotic fluid, and are detected by three commercially-available immunoassays used for diagnosing ruptured membranes: Actim PROM®, Amnisure®, and ROM Plus®. We used whole blood samples and diluted these with amniotic fluid (containing known concentrations of amniotic fluid proteins) to whole blood levels of 50, 20, 10, 5, and 1%. Actim PROM®, Amnisure®, and ROM Plus® tests were performed on each sample in duplicate according to package insert instructions. Results were interpreted independently at 5, 10, 15, and 20 min by two obstetricians who were blinded to the concentrations of blood and amniotic fluid proteins in each sample. Results of each test were determined to be true positive, false negative, false positive, or true negative based on physician interpretation and whether amniotic fluid had been spiked into the samples in detectable concentrations. Overall accuracy, intraobserver concordance, and interobserver concordance, sensitivity, specificity, and predictive values for each test were calculated. Fisher exact test was used to compare test characteristics, with a p-value of <.05 considered significant.Results: Out of 120 tests performed, there were no false positive results for any test. Overall, ROM Plus® had better accuracy (97.9%) than Amnisure® (80.7%) or Actim® PROM (78.3%). Intra- and interobserver concordance were similar for all three tests (98-100%). ROM Plus® had significantly higher sensitivity than Amnisure® and Actim® PROM (p < .0001). There was no significant difference in sensitivity between Amnisure® and Actim® PROM (p = .51).Conclusion: ROM Plus® maintains strong test characteristics for the detection of amniotic fluid proteins in the setting of blood contamination, and performs significantly better than Amnisure® and Actim® PROM tests in the presence of blood.