Performance of a wearable acoustic system for fetal movement discrimination

Abstract

Fetal movements (FM) are a key factor in clinical management of high-risk pregnancies such as fetal growth restriction. While maternal perception of reduced FM can trigger self-referral to obstetric services, maternal sensation is highly subjective. Objective, reliable monitoring of fetal movement patterns outside clinical environs is not currently possible. A wearable and non-transmitting system capable of sensing fetal movements over extended periods of time would be extremely valuable, not only for monitoring individual fetal health, but also for establishing normal levels of movement in the population at large. Wearable monitors based on accelerometers have previously been proposed as a means of tracking FM, but such systems have difficulty separating maternal and fetal activity and have not matured to the level of clinical use. We introduce a new wearable system based on a novel combination of accelerometers and bespoke acoustic sensors as well as an advanced signal processing architecture to identify and discriminate between types of fetal movements. We validate the system with concurrent ultrasound tests on a cohort of 44 pregnant women and demonstrate that the garment is capable of both detecting and discriminating the vigorous, whole-body ‘startle’ movements of a fetus. These results demonstrate the promise of multimodal sensing for the development of a low-cost, non-transmitting wearable monitor for fetal movements.

A Novel Fetal Movement Simulator for the Performance Evaluation of Vibration Sensors for Wearable Fetal Movement Monitors

“…However, the main peak occurred around 2 Hz in the case of the acoustic sensor and around 19 Hz in the case of the accelerometer. This PSD distribution of the acoustic signal also conforms with the PSD distribution obtained from the acoustic signals due to the real fetal kicks, as reported by Lai et al [26].…”

“…The acoustic sensor tested on the FM simulator is similar to the sensors used by Lai et al [26] in their wearable FM monitor. The design of this sensor was originally adapted from the design first presented by Posatskiy and Chau [43].…”

“…By experimenting with six accelerometers, Altini et al [25] reported that the addition of accelerometers after two does not improve the detection accuracy significantly, while the addition of a reference accelerometer to remove artefacts due to maternal activity consistently improves the detection accuracy for any number and arrangement of sensors. In a recent work from our group, Lai et al [26] presented a new design of FM monitor based on a combination of six acoustic sensors and an inertial measurement unit (IMU). The IMU mainly consisted of an accelerometer, which was used to detect maternal body movements.…”

“…Although extensive efforts have been made to design FM monitors using accelerometers, the desired accuracy of detection has not been achieved and translation remains negligible. Our recent study indicates that while acoustic sensing is promising, the false-positive detection remains unacceptably high [26]. Therefore, it is important now to quantify the limitations of these sensors, look for new candidate sensors, and consider a combination of different types of sensors to further improve the accuracy of detection.…”

Neuroimaging perspectives on fetal motor behavior

“…[80][81][82] Attempts to devise wearable technology to detect patterns of motor behaviour still demonstrate an accuracy of between 40-80%. 83 Though there may be a limited role for FMC as…”