A systematic scoping review to identify the design and assess the performance of devices for antenatal continuous fetal monitoring.

BACKGROUND: Antepartum fetal monitoring aims to assess fetal development and wellbeing throughout pregnancy. Current methods utilised in clinical practice are intermittent and only provide a 'snapshot' of fetal wellbeing, thus key signs of fetal demise could be missed. Continuous fetal monitoring (CFM) offers the potential to alleviate these issues by providing an objective and longitudinal overview of fetal status. Various CFM devices exist within literature; this review planned to provide a systematic overview of these devices, and specifically aimed to map the devices' design, performance and factors which affect this, whilst determining any gaps in development. METHODS: A systematic search was conducted using MEDLINE, EMBASE, CINAHL, EMCARE, BNI, Cochrane Library, Web of Science and Pubmed databases. Following the deletion of duplicates, the articles' titles and abstracts were screened and suitable papers underwent a full-text assessment prior to inclusion in the review by two independent assessors. RESULTS: The literature searches generated 4,885 hits from which 43 studies were included in the review. Twenty-four different devices were identified utilising four suitable CFM technologies: fetal electrocardiography, fetal phonocardiography, accelerometry and fetal vectorcardiography. The devices adopted various designs and signal processing methods. There was no common means of device performance assessment between different devices, which limited comparison. The device performance of fetal electrocardiography was reduced between 28 to 36 weeks' gestation and during high levels of maternal movement, and increased during night-time rest. Other factors, including maternal body mass index, fetal position, recording location, uterine activity, amniotic fluid index, number of fetuses and smoking status, as well as factors which affected alternative technologies had equivocal effects and require further investigation. CONCLUSIONS: A variety of CFM devices have been developed, however no specific approach or design appears to be advantageous due to high levels of inter-device and intra-device variability.

Maternal perception of fetal movements in late pregnancy is affected by type and duration of fetal movement.

OBJECTIVE: A reduction in fetal movements has been proposed to identify pregnancies at risk of stillbirth. The utility of this approach is limited by variability in maternal perception of fetal movements. We aimed to determine the proportion of fetal movements observed by ultrasound that were maternally perceived and identify factors that affected maternal perception. METHOD: During 30-min recordings, women (n = 21) depressed a trigger upon perception of a fetal movement, while an ultrasound operator recorded observed movements according to the fetal parts involved. RESULTS: Women perceived between 2.4% and 81.0% (median 44.8%) of movements observed on scan. Synchronous movement of the fetal trunk and limbs was more likely to be recognized than either part in isolation (60.5% versus 37.5% and 30%, respectively). The ultrasound operator judged the fetus to be moving for a significantly greater proportion of the time than mothers (median 1.5% of total recording time versus 0.7%). There was no significant relationship between the ability to perceive fetal activity and placental site, parity, amniotic fluid index or maternal body mass index. CONCLUSION: Variations in maternal perception of fetal movements may affect detection of a clinically significant reduction in fetal movements for some women.

Continuous objective recording of fetal heart rate and fetal movements could reliably identify fetal compromise, which could reduce stillbirth rates by facilitating timely management.

Stillbirth currently affects approximately 1 in every 200 pregnancies in the United Kingdom. Fetuses may exhibit signs of compromise as part of a stress response before stillbirth, including reduced fetal movements (RFM) and fetal heart rate (FHR) alterations. At present, and despite widespread use, current fetal monitoring is not associated with a reduction in perinatal mortality rate (PMR) as signs of fetal compromise are not adequately detected. This may be attributed to inaccuracies resulting from manual interpretation of results or subjective assessment of fetal activity. In addition, signs of compromise often occur only hours or days before fetal death, so may be missed by current monitoring methods, which are performed intermittently. A significant consideration is that correct identification of these signs and consequent intervention can result in the delivery of a healthy baby, thus preventing stillbirth. A hypothesis is presented, proposing prompt detection of fetal compromise with the use of 24-hour continuous objective fetal monitoring. With focus placed on obtaining long-term FHR and fetal movement data, prior interest has been found in developing devices for this purpose. However, introduction into clinical practice has not been achieved. Investigation of the hypothesis will begin with the design of a device to record the mentioned parameters, followed by an appropriate validation process. Should development and testing be successful, an eventual comparison in PMR with the use of continuous fetal monitoring vs current monitoring would address the hypothesis. It is suggested that a timely yet reliable indication of fetal wellbeing obtained via long-term monitoring would allow prompt and appropriate obstetric intervention and consequently reduce PMR.

VLSI circuits implementing computational models of neocortical circuits.

This paper overviews the design and implementation of three neuromorphic integrated circuits developed for the COLAMN ("Novel Computing Architecture for Cognitive Systems based on the Laminar Microcircuitry of the Neocortex") project. The circuits are implemented in a standard 0.35 µm CMOS technology and include spiking and bursting neuron models, and synapses with short-term (facilitating/depressing) and long-term (STDP and dopamine-modulated STDP) dynamics. They enable execution of complex nonlinear models in accelerated-time, as compared with biology, and with low power consumption. The neural dynamics are implemented using analogue circuit techniques, with digital asynchronous event-based input and output. The circuits provide configurable hardware blocks that can be used to simulate a variety of neural networks. The paper presents experimental results obtained from the fabricated devices, and discusses the advantages and disadvantages of the analogue circuit approach to computational neural modelling.

Neuromorphic silicon neuron circuits.

Hardware implementations of spiking neurons can be extremely useful for a large variety of applications, ranging from high-speed modeling of large-scale neural systems to real-time behaving systems, to bidirectional brain-machine interfaces. The specific circuit solutions used to implement silicon neurons depend on the application requirements. In this paper we describe the most common building blocks and techniques used to implement these circuits, and present an overview of a wide range of neuromorphic silicon neurons, which implement different computational models, ranging from biophysically realistic and conductance-based Hodgkin-Huxley models to bi-dimensional generalized adaptive integrate and fire models. We compare the different design methodologies used for each silicon neuron design described, and demonstrate their features with experimental results, measured from a wide range of fabricated VLSI chips.

Compact silicon neuron circuit with spiking and bursting behaviour.

A silicon neuron circuit that produces spiking and bursting firing patterns, with biologically plausible spike shape, is presented. The circuit mimics the behaviour of known classes of cortical neurons: regular spiking (RS), fast spiking (FS), chattering (CH) and intrinsic bursting (IB). The paper describes the operation of the circuit, provides simulation results, a simplified analytical model, and a phase-plane analysis of its behaviour. The functionality of the circuit has been verified experimentally. The paper introduces a proof-of-concept analogue integrated circuit, implemented in a 0.35 microm CMOS technology, and presents preliminary measurement results. The neuron cell provides an area and energy efficient implementation of the silicon cortical neuron, and could be used as a universal neuron circuit in VLSI neuromorphic networks that closely resemble the circuits of the cortex.