Feasibility of antenatal ambulatory fetal electrocardiography: a systematic review.

BACKGROUND: Antenatal fetal heart rate (FHR) monitoring is currently limited by hospital-based accessibility as well as the availability of relevant equipment and expertise required to position device electrodes. Ambulatory FHR monitoring in the form of noninvasive fetal electrocardiography (NIFECG) is currently an area of research interest, particularly during the era of the COVID-19 pandemic, and the potential to improve maternity care and reduce hospital attendances need to be evaluated.

OBJECTIVES: To assess the feasibility, acceptability, and signal success of ambulatory NIFECG monitoring and identify research areas required to facilitate clinical utilization of this method of monitoring.

METHODS: Medline, EMBASE, and PubMed databases were searched from January 2005 to April 2021 using terms relevant to antenatal ambulatory or home NIFECG. The search was compliant with PRISMA guidelines, and was registered with the PROSPERO database (CRD42020195809). All studies reporting the clinical utilization of NIFECG inclusive of its use in the ambulatory setting performed in the antenatal period, human studies, and those in the English language were included. Those reporting novel technological methods and electrophysiological algorithms, satisfaction surveys, intrapartum studies, case reports and reviews, and animal studies were excluded. Study screening and data extraction were conducted in duplicate. Risk of bias was appraised using the Modified Downs and Black tool. Due to the heterogeneity of the reported findings, a meta-analysis was not feasible.

RESULTS: The search identified 193 citations, where 11 studies were deemed eligible for inclusion. All studies used a single NIFECG system with a duration of monitoring ranging from 5.6 to 21.4 h. Predefined signal acceptance threshold ranged from 34.0-80.0%. Signal success in the study populations was 48.6-95.0% and was not affected by maternal BMI. Good signals were achieved in the 2nd trimester, but less so in the early 3rd trimester. NIFECG was a well-accepted method of FHR monitoring, with up to 90.0% of women's satisfaction levels when worn during outpatient induction of labor. Placement of the acquisition device needed input from healthcare staff in every report.

CONCLUSIONS: Although there is evidence for the clinical feasibility of ambulatory NIFECG, the disparity in the literature limits the ability to draw firm conclusions. Further studies to establish repeatability and device validity, whilst developing standardized FHR parameters and set evidence-based standards for signal success for NIFECG are required to ascertain the clinical benefit and potential limitations of ambulatory outpatient FHR monitoring.