PORTABLE AND CONTINUOUS MONITORING DEVICES IN FETAL MEDICINE: TECHNOLOGICAL ADVANCEMENTS, CLINICAL APPLICATIONS, AND CURRENT LIMITATIONS

: Fetal medicine has witnessed significant advancements with the development of portable and continuous monitoring devices. These devices offer a promising alternative to traditional methods, often intermittent and limited to hospital settings. This narrative review explores the technological advancements, clinical applications, and current limitations of portable and continuous monitoring devices in fetal medicine. We conducted a comprehensive literature search using databases such as Scopus, Web of Science, PubMed, and ScienceDirect to identify relevant studies. The results highlight innovative monitoring systems, including wireless and flexible sensor networks, non-invasive fetal electrocardiography (NIFECG) devices, and telemetry systems. These devices have successfully monitored vital maternal and fetal signs, provided continuous and non-invasive monitoring, and improved patient comfort and mobility. However, current technological limitations, such as signal quality issues, motion artifacts, performance variability, design constraints, and environmental and maternal factors, still impact their effectiveness and clinical applicability. The discussion emphasizes the potential of these devices to revolutionize fetal medicine by offering more accurate and less invasive surveillance, particularly in high-risk contexts. However, continuous advancements in device development are necessary to overcome the identified limitations and improve accuracy, usability, and clinical acceptance. Integrating portable and constant monitoring devices into clinical practice can potentially enhance maternal and fetal outcomes significantly.


INTRODUCTION
Fetal medicine has undergone a remarkable transformation with the advent of portable and continuous monitoring devices.These innovative technologies offer a paradigm shift from traditional intermittent monitoring methods, often confined to hospital settings.Portable and 1 UNIRV-campus Rio Verde -GO. 2 PUCRS. 3Santa Casa de Misericórdia de Vitoria Higher School of Sciences -EMESCAM.Santa Luíza -Vitória -ES -Brazil, Molecular Dynamics and Modeling Laboratory (DynMolLab) 4 Molecular Dynamics and Modeling Laboratory (DynMolLab), Santa Luíza -Vitória -ES -Brazil constant monitoring devices provide real-time, non-invasive maternal and fetal well-being surveillance, enabling early detection of potential complications and timely interventions [1].This narrative review explores the technological advancements, clinical applications, and current limitations of portable and continuous monitoring devices in fetal medicine.
The importance of continuous fetal monitoring cannot be overstated, particularly in high-risk pregnancies.Conventional methods, such as intermittent auscultation and cardiotocography (CTG), have limitations in providing continuous surveillance and detecting subtle changes in fetal well-being [2].Moreover, these methods often require the mother to be confined to a hospital bed, restricting her mobility and comfort.Portable and continuous monitoring devices address these challenges by offering a more patient-centric approach, allowing for monitoring in various settings, including home environments [3].
Advancements in sensor technology, wireless communication, and data analytics have fueled the development of portable and continuous monitoring devices.These devices incorporate various sensing modalities, such as electrocardiography, electromyography, and accelerometry, to capture vital maternal and fetal parameters [4].The collected data is transmitted wirelessly to a central monitoring system, enabling real-time analysis and alerting healthcare providers to potential abnormalities.This review aims to provide a comprehensive overview of the current state of portable and continuous monitoring devices in fetal medicine.We will discuss the technological advancements, highlighting specific devices and their features.The clinical applications of these devices will be explored, emphasizing their potential to improve maternal and fetal outcomes.Additionally, we will address the current limitations and challenges associated with these technologies, identifying areas for future research and development.

METHODOLOGY
A comprehensive literature search was conducted to identify relevant studies on portable and continuous monitoring devices in fetal medicine.The following electronic databases were searched: Scopus, Web of Science, PubMed, and ScienceDirect.The search strategy included a combination of keywords such as "fetal monitoring," "portable devices," "continuous monitoring," "wireless sensors," "non-invasive," "telemetry," and "fetal medicine." The inclusion criteria for the selected studies were as follows: (1) original research articles, review articles, or conference proceedings; (2) studies focusing on portable or continuous monitoring devices in fetal medicine; (3) studies published in English; and (4) studies published between 2000 and 2024.The exclusion criteria were: (1) studies not directly related to fetal monitoring or fetal medicine; (2) studies focusing solely on traditional monitoring methods; and (3) non-peer-reviewed sources.
The initial search yielded a total of 572 articles.After removing duplicates and applying the inclusion and exclusion criteria, 38 articles were selected for further review.The selected articles were thoroughly examined, and relevant information was extracted, including device descriptions, technological features, clinical applications, and study outcomes.The extracted data was synthesized and organized into thematic categories for the narrative review.

Wireless and Flexible Sensor Networks
One notable advancement in portable and continuous fetal monitoring is the development of wireless and flexible sensor networks.These systems integrate multiple lowprofile sensors to continuously monitor vital maternal and fetal signs.Ryu et al. [5] described a comprehensive pregnancy monitoring system that utilizes a network of wireless, soft, and flexible sensors.This system incorporates three sensors: a cuffless continuous blood pressure monitor, an electrohysterography-derived uterine monitoring sensor, and an automated body position classification sensor.The study demonstrated the successful testing of this system in both high-and low-resource health settings, showcasing its performance, usability, and safety.
The wireless and flexible sensor network approach offers several advantages over traditional monitoring methods.Firstly, the low-profile and flexible nature of the sensors enhances patient comfort, allowing for prolonged monitoring periods without causing discomfort or restricting mobility [6].Secondly, wireless data transmission enables remote monitoring, reducing the need for frequent hospital visits and facilitating home-based tracking [7].Lastly, integrating multiple sensors provides a comprehensive assessment of maternal and fetal well-being, enabling the detection of a wide range of potential complications [5].Firstly, they eliminate the need for invasive procedures, such as scalp electrode placement, reducing the risk of infection and other complications [10].Secondly, NIFECG devices allow for continuous monitoring, providing a more comprehensive assessment of fetal well-being than intermittent auscultation [11].Lastly, the non-invasive nature of these devices enables monitoring in various settings, including home environments, promoting patient comfort and convenience [12].

Telemetry Systems for Fetal Monitoring
Telemetry systems have emerged as a promising approach for continuous fetal monitoring, particularly during labor and delivery.These systems utilize wireless technology to transmit fetal heart rate and uterine contraction data from the mother to a remote monitoring station [13].Neuman et al. [14] evaluated a radiotelemetry system that continuously monitors fetal heart rate and intrauterine pressure during labor, providing increased patient comfort and mobility.
Telemetry systems offer several benefits in fetal monitoring.Firstly, they enable continuous surveillance of fetal well-being, allowing for early detection of potential complications and timely interventions [15].Secondly, telemetry systems promote patient mobility, as the mother is not tethered to a bedside monitor, enhancing comfort and facilitating natural labor positions [16].Lastly, these systems reduce the need for frequent manual assessments, optimize healthcare provider workload, and enable more efficient labor management [17].

Clinical Applications and Potential Impact
Portable and continuous monitoring devices have numerous clinical applications in fetal medicine, particularly high-risk pregnancies.These devices can be utilized for various indications, including: Fetal growth restriction: Continuous monitoring of fetal well-being is crucial in cases of fetal growth restriction to detect signs of fetal compromise and guide management decisions [18].
Preterm labor: Portable devices can aid in the early detection of preterm labor, enabling timely interventions to prolong pregnancy and improve neonatal outcomes [19].
Gestational diabetes: Continuous glucose monitoring devices can assist in managing gestational diabetes, optimizing glycemic control, and reducing the risk of adverse outcomes [20].
High-risk pregnancies: Portable and continuous monitoring devices are precious in high-risk pregnancies, such as those complicated by hypertensive disorders, multiple gestations, or fetal anomalies [21].
The potential impact of these devices on maternal and fetal outcomes is significant.By providing continuous surveillance and early detection of complications, portable monitoring devices can facilitate timely interventions, potentially reducing the risk of adverse events such as fetal distress, neonatal morbidity, and stillbirth [22].Moreover, these devices can enhance patient satisfaction and engagement by promoting comfort, mobility, and home-based monitoring [23].

Current Limitations and Challenges
Despite the promising advancements in portable and continuous fetal monitoring devices, several limitations and challenges persist.These include: Signal quality issues: The quality of signals obtained from devices like NIFECG can be compromised by maternal body mass index (BMI), fetal and maternal movements, and gestational age [24].Studies have shown that signal loss can be significant, particularly in early gestational ages and women with high BMI [25].
Motion artifacts: Maternal and fetal movements can introduce artifacts in the acquired signals, reducing monitoring accuracy [26].This is particularly problematic during high uterine and fetal activity [27].
Performance variability: There is substantial variability in the performance of monitoring devices across different technologies and even among other models of the same device type [28].This lack of standardization hinders direct comparisons and clinical decisionmaking [29].
Design limitations: Many devices are still bulky or uncomfortable for prolonged use, limiting patient compliance with continuous monitoring [30].Additionally, inadequate sensor fixation can result in signal loss and incomplete data acquisition [31].
Environmental and maternal factors: Fetal position, recording location, uterine activity, and amniotic fluid index can also affect signal quality and data accuracy [32].
Technological improvements: Devices like the VisiBeam for continuous fetal cerebral blood flow monitoring still require transducer design and fixation enhancements to ensure signal quality in a more significant proportion of fetuses during labor [33].Integrating artificial intelligence and machine learning algorithms can potentially optimize signal processing, pattern recognition, and decision support [34].Additionally, developing multimodal monitoring systems that combine various sensing modalities, such as electrocardiography, ultrasound, and bioimperimetry, can provide a more comprehensive assessment of fetal well-being [35].
The successful implementation of portable and continuous fetal monitoring devices in clinical practice requires a multidisciplinary approach involving collaboration among healthcare providers, engineers, and device manufacturers.Establishing guidelines and protocols for device use, interpretation of data, and clinical decision-making is essential to ensure consistent and evidence-based practice [36].Moreover, healthcare provider training and education on properly using and interpreting these devices are crucial for practical integration into clinical workflows [37].

CONCLUSION
Portable and continuous monitoring devices have emerged as a promising frontier in fetal medicine, offering a non-invasive and patient-centric approach to fetal surveillance.
Technological advancements in wireless and flexible sensor networks, NIFECG devices, and telemetry systems have enabled continuous maternal and fetal well-being monitoring, promoting early detection of complications and timely interventions.These devices have the potential to significantly improve maternal and fetal outcomes, particularly in high-risk pregnancies.
However, these devices' current limitations and challenges, such as signal quality issues, motion artifacts, performance variability, and design constraints, necessitate ongoing research and development efforts.Addressing these limitations through technological enhancements, standardization, and multidisciplinary collaboration is crucial for successfully integrating these devices into clinical practice.
Non-Invasive Fetal Electrocardiography (NIFECG) DevicesAnother significant advancement in fetal monitoring is the development of noninvasive fetal electrocardiography (NIFECG) devices.These devices capture the fetal electrocardiogram signal through electrodes placed on the maternal abdomen, providing a noninvasive means of monitoring fetal heart rate and rhythm[8].Eenkhoorn et al.[9] evaluated the performance and patient experience of two NIFECG devices: the Nemo Fetal Monitoring System and the Philips Avalon-Beltless.The study found that these devices were suitable for prolonged fetal heart rate monitoring, offering increased comfort and mobility compared to traditional CTG.NIFECG devices have several advantages over conventional fetal monitoring methods.
These limitations highlight the need for ongoing advancements in device development to improve accuracy, usability, and clinical acceptance.DISCUSSIONThe development of portable and continuous monitoring devices represents a significant milestone in fetal medicine, offering a paradigm shift from traditional intermittent monitoring methods.These devices provide real-time, non-invasive maternal and fetal wellbeing surveillance, enabling early detection of potential complications and timely interventions.The integration of wireless and flexible sensor networks, NIFECG devices, and telemetry systems has revolutionized fetal monitoring, enhancing patient comfort, mobility, and access to care.The clinical applications of these devices are diverse, ranging from monitoring fetal growth restriction and preterm labor to managing gestational diabetes and high-risk pregnancies.The potential impact on maternal and fetal outcomes is substantial, as continuous surveillance facilitates early intervention and reduces the risk of adverse events.Moreover, these devices promote patient-centered care by allowing for home-based monitoring and reducing the need for frequent hospital visits.However, it is crucial to acknowledge the current limitations and challenges associated with portable and continuous fetal monitoring devices.Signal quality issues, motion artifacts, performance variability, design limitations, and environmental and maternal factors can impact the accuracy and reliability of these devices.Addressing these limitations requires ongoing research and development efforts to improve device design, signal processing algorithms, and standardization.Future advancements in portable and continuous fetal monitoring devices should enhance signal quality, minimize motion artifacts, and improve device comfort and usability.