Comparison of fetal and maternal heart rate measures using electrocardiographic and cardiotocographic methods

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.

Baseline heart rate in infants with prenatal alcohol exposure: A systematic review and independent analysis

BACKGROUND

Infants with fetal alcohol syndrome exhibit a range of developmental anomalies, many related to the heart (e.g., decreased heart rate variability). However, the baseline heart rate in this population remains unclear. We hypothesized that the age at which heart rate was measured or the age during exposure to alcohol affects the baseline heart rate.

METHODS

First, we conducted a systemic review to determine the published heart rate of infants with prenatal alcohol exposure (PAE). Exclusion criteria included potentially confounding factors, including the commonly associated phenotypes of small for gestational age and premature birth. Risk of bias was evaluated based on case study limitations, and data were compared with established heart rate norms. Then, we evaluated the precise age at heart rate measurement using existing datasets from the Collaborative Initiative on Fetal Alcohol Spectrum Disorders and the Maternal Lifestyle Study.

RESULTS

Based on the weighted means of six studies, the baseline heart rate was 4.6 bpm higher in infants with PAE (n = 253) than in control infants (n = 152). Using the individual patient data, baseline heart rates were similar between age-matched infants with PAE and control infants who were born full-term and showed no signs of growth restriction (ANOVA, p > .05; n = 49-124 infants per age and exposure).

CONCLUSIONS

A systematic literature review suggested that heart rate is elevated in infants with PAE, but these findings are limited by the number of studies and how few studies included control infants. The analysis of individual patient data indicates that infants with PAE have normal baseline heart rates. This knowledge may help clinicians detect changes in cardiac function in infants with PAE. (Registered via PROSPERO, #CRD42020191212.).

Fetal heart rate during maternal sleep

Despite prolonged and cumulative exposure during gestation, little is known about the fetal response to maternal sleep. Eighty-four pregnant women with obesity (based on pre-pregnancy BMI) participated in laboratory-based polysomnography (PSG) with continuous fetal electrocardiogram monitoring at 36 weeks gestation. Multilevel modeling revealed both correspondence and lack of it in maternal and fetal heart rate patterns. Fetal heart rate (fHR) and variability (fHRV), and maternal heart rate (mHR) and variability (mHRV), all declined during the night, with steeper rates of decline prior to 01:00. fHR declined upon maternal sleep onset but was not otherwise associated with maternal sleep stage; fHRV differed during maternal REM and NREM. There was frequent maternal waking after sleep onset (WASO) and fHRV and mHRV were elevated during these episodes. Cross-correlation analyses revealed little temporal coupling between maternal and fetal heart rate, except during WASO, suggesting that any observed associations in maternal and fetal heart rates during sleep are the result of other physiological processes. Implications of the maternal sleep context for the developing fetus are discussed, including the potential consequences of the typical sleep fragmentation that accompanies pregnancy.

Is portable foetal electrocardiogram monitor feasible for foetal heart rate monitoring of small for gestational age foetuses in the home environment

Small-for-gestational-age (SGA) foetuses are at greater risk of complications than normal foetuses. Studies have demonstrated that foetal electrocardiogram (ECG) device (Monica-AN24) can be employed for monitoring foetal heart rate (FHR). However, its reliability and acceptability has not been assessed in SGA foetuses. This study was aimed at: (a) determining the acceptability of wearing the device more than once, (b) investigating the reliability of acquiring successful FHR data at different gestation. Patients with singleton non-anomalous foetus >24 weeks gestation and an estimated foetal weight below tenth percentile were recruited. Thirty-five women wore the device once. Twenty-four of these wore second time (68.6%). Overall, success-rate of FHR signals was 48.6% and increased to 68.8% beyond 34 weeks gestation. Foetal ECG is a promising method for monitoring SGA foetus >34 weeks gestation. Compared to day recordings, foetal signals were more reliable at night. Further studies are required before its clinical utility can be ascertained. IMPACT STATEMENT What is already known on this subject? Pregnancies that are affected by small-for-gestational-age (SGA) foetus pose a major public health problem and are associated with increased perinatal morbidity and mortality. There is no consensus on the optimal timing of delivery. Current methods employed for monitoring SGA foetuses include ultrasound scans for foetal-biometry and Doppler assessments. However, they provide a snapshot of information on foetal well-being, restrict patient mobility and cannot be employed over long-time periods. It is plausible that ambulatory foetal-ECG device that enable monitoring over a longer time period may better inform decisions about the timing of delivery. What do the results of this study add? Trans-abdominal foetal-ECG is a promising method of monitoring SGA foetus in the home setting with a success rate of acquiring reliable foetal heart rate (FHR) data over 90% at night time. What are the implications of these findings for clinical practice and/or further research? Overall, the study approved the concept of long-term home monitoring and has highlighted the facilitators and barriers to wearing the monitor in clinical care. These observations can be used to undertake robust research to assess the use of foetal-ECG monitor singly or in conjunction with current monitoring techniques for optimal foetal surveillance.

A mixed-methods evaluation of continuous electronic fetal monitoring for an extended period

INTRODUCTION

Continuous fetal monitoring is used to objectively record the fetal heart rate and fetal activity over an extended period of time; however, its feasibility and acceptability to women is currently unknown. The study addressed the hypothesis that continuous fetal monitoring is feasible and acceptable to pregnant women.

MATERIAL AND METHODS

Pregnant participants (n = 22) were monitored using a continuous fetal electrocardiography device, the Monica AN24. Signal quality, duration of recording and cardiotocography findings were correlated with maternal and fetal factors. Participants' change in anxiety before and after monitoring was assessed using validated questionnaires. Participants' experiences were explored through a questionnaire (n = 20) and semi-structured interview (n = 13).

RESULTS

Recordings were successfully obtained in 19 of the 22 participants (86.3%). The mean recording quality of fetal heart rate was 69.0% (range 17.4%-99.4%) and maternal heart rate was 99.0% (90.9%-100.0%). Recording quality was positively correlated with gestational age (P = 0.05) and negatively correlated with uterine activity and maternal movement (P < 0.001). Overall, participants were satisfied with their experience of continuous fetal monitoring; 30% considered it preferable to intermittent monitoring. Continuous fetal monitoring did not significantly increase maternal anxiety, with a trend towards a reduction in Pregnancy Specific Anxiety score (P = 0.07). Qualitative analysis grouped women's responses into three themes: (a) reassurance and anxiety, (b) the physical device and (c) future developments in continuous fetal monitoring.

CONCLUSIONS

Continuous fetal monitoring is a feasible and acceptable form of monitoring to pregnant women although further practical improvements could be incorporated. Further research is required to assess the ability of continuous fetal monitoring to detect fetal compromise.