This research was published in the AJOG, June 9, 2023 here.

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Objective

The need for serial in-office nonstress tests (NSTs) adds substantial burden to high-risk pregnancies and exacerbates care disparities.INVU by Nuvo Group, Ltd, is a novel Food and Drug Administration-cleared, remote, self-administered maternal-fetal monitoring solution, previously validated for fetal and maternal heart rates and uterine activity measurements. Here, we sought to determine the clinical interpretability and usability of INVU to enable patients to perform NSTs from home.

Study Design

This was a prospective, open-label, single-site study of a wireless, remote pregnancy monitoring system (INVU by Nuvo Group, Ltd) in high-risk pregnancies to remotely perform clinically indicated NSTs instead of in-clinic NSTs. This study was approved by the University of Pennsylvania Institutional Review Board, and participants provided informed consent.

The INVU belt contains 8 biopotential and 4 acoustic sensors, which passively record abdominal signals (Figure, A). The monitoring system includes a Health Insurance Portability and Accountability Act–compliant mobile application that allows clinicians to view and interpret the NST and communicate with the patient in real time (Figure, B).

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We enrolled singleton pregnancies at ≥32 weeks of gestation with clinical indications for antenatal fetal surveillance, pregravid body mass indices (BMIs) of ≤50 and ≥15 kg/m², and Wi-Fi access. Exclusions were uncontrolled hypertension, major fetal anomaly, abdominal skin issues, or an implanted electronic device.

The primary outcome was whether the remote NST was deemed acceptable for clinical utility (interpretability). For the secondary outcomes, we evaluated reactivity rates among NSTs deemed clinically acceptable (reactivity) and the frequency and reason for recommending an in-clinic evaluation. Moreover, participants completed the validated System Usability Scale (SUS).

Descriptive analyses were performed using SAS (version 9.4; SAS Institute, Cary, NC).

Results

We enrolled 34 high-risk patients at a mean gestational age of 34.5±1.1 weeks and a BMI of 35.8±6.3 kg/m² from December 10, 2020, to March 6, 2022. Fetal testing indications included advanced maternal age (n=14), BMI of ≥40 kg/m² (n=11), gestational diabetes mellitus (n=10), chronic hypertension (n=3), antiphospholipid syndrome (n=2), and other (n=9).

Of note, 5 consented patients failed to complete device training. The remaining 29 patients had 131 qualifying remote NST sessions. INVU successfully obtained an interpretable NST in 93.9% of appointments (n=123), of which 98.3% (n=121) were deemed reactive. Patients avoided an in-office visit in 88.5% of visits. Only 2 appointments (1.5%) resulted in a recommendation for nonurgent delivery, both for elevated blood pressure and neither related to the NST tracing. Only 1 patient (2.9%) experienced mild, transient soreness at the sensor site without redness or bruising.

Of note, 23 patients (79.3%) who attempted at least 1 remote NST completed the SUS, with a mean score of 76.5 (±15.9) of 100.0, indicating “good” usability, with 22 patients (95.7%) agreeing they would prefer remote NSTs vs in-office testing in a future pregnancy. Further details and discussion are available in the Supplemental Materials and Methods.

Conclusion

In this prospective cohort study, >90% of NSTs performed remotely using INVU were acceptable for clinical utility, and >88% of NST appointments were completed without in-clinic evaluation. In addition, INVU demonstrated an excellent safety profile and good patient usability. Future research is warranted to determine how to best leverage this novel capability to address inequities in patient access and improve perinatal outcomes.

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