Fetal heart rate development during labour

BACKGROUND

Fresh stillbirths (FSB) and very early neonatal deaths (VEND) are important global challenges with 2.6 million deaths annually. The vast majority of these deaths occur in low- and low-middle income countries. Assessment of the fetal well-being during pregnancy, labour, and birth is normally conducted by monitoring the fetal heart rate (FHR). The heart rate of newborns is reported to increase shortly after birth, but a corresponding trend in how FHR changes just before birth for normal and adverse outcomes has not been studied. In this work, we utilise FHR measurements collected from 3711 labours from a low and low-middle income country to study how the FHR changes towards the end of the labour. The FHR development is also studied in groups defined by the neonatal well-being 24 h after birth.

METHODS

A signal pre-processing method was applied to identify and remove time periods in the FHR signal where the signal is less trustworthy. We suggest an analysis framework to study the FHR development using the median FHR of all measured heart rates within a 10-min window. The FHR trend is found for labours with a normal outcome, neonates still admitted for observation and perinatal mortality, i.e. FSB and VEND. Finally, we study how the spread of the FHR changes over time during labour.

RESULTS

When studying all labours, there is a drop in median FHR from 134 beats per minute (bpm) to 119 bpm the last 150 min before birth. The change in FHR was significant ([Formula: see text]) using Wilcoxon signed-rank test. A drop in median FHR as well as an increased spread in FHR is observed for all defined outcome groups in the same interval.

CONCLUSION

A significant drop in FHR the last 150 min before birth is seen for all neonates with a normal outcome or still admitted to the NCU at 24 h after birth. The observed earlier and larger drop in the perinatal mortality group may indicate that they struggle to endure the physical strain of labour, and that an earlier intervention could potentially save lives. Due to the low amount of data in the perinatal mortality group, a larger dataset is required to validate the drop for this group.

Concordance analysis of intrapartum cardiotocography between physicians and artificial intelligence-based technique using modified one-dimensional fully convolutional networks

BACKGROUND

Cardiotocography is a common method of electronic fetal monitoring (EFM) for fetal well-being. Data-driven analyses have shown potential for automated EFM assessment. For this preliminary study, we used a novel artificial intelligence method based on fully convolutional networks (FCNs), with deep learning for EFM evaluation and correct recognition, and its possible role in evaluation of nonreassuring fetal status.

METHODS

We retrospectively collected 3239 EFM labor records from 292 deliveries and neonatal Apgar scores between December 2018 and July 2019 at a single medical center. We analyzed these data using an FCN model and compared the results with clinical practice.

RESULTS

The FCN model recognized EFM traces like physicians, with an average Cohen's kappa coefficient of agreement of 0.525 and average area under the receiver operating characteristic curve of 0.892 for six fetal heart rate (FHR) categories. The FCN model showed higher sensitivity for predicting fetal compromise (0.528 vs 0.132) but a higher false-positive rate (0.632 vs 0.012) compared with clinical practice.

CONCLUSION

FCN is a modern technique that may be useful for EFM trace recognition based on its multiconvolutional layered analysis. Our model showed a competitive ability to identify FHR patterns and the potential for evaluation of nonreassuring fetal status.

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.

A new microdialysis probe for continuous lactate measurement during fetal monitoring: Proof of concept in an animal model

INTRODUCTION

Cardiotocography (CTG) is currently the most commonly used method for intrapartum fetal monitoring during labor. However, a high false-positive rate of fetal acidosis indicated by CTG leads to an increase in obstetric interventions. We developed a microdialysis probe that is integrated into a fetal scalp electrode allowing continuous measurement of lactate subcutaneously, thus giving instant information about the oxygenation status of the fetus. Our aim was to establish proof of concept in an animal model using a microdialysis probe to monitor lactate subcutaneously.

MATERIAL AND METHODS

We performed an in vivo study in adult male wild-type Wistar rats. We modified electrodes used for CTG monitoring in human fetuses to incorporate a microdialysis membrane. Optimum flow rates for microdialysis were determined in vitro. For the in vivo experiment, a microdialysis probe was inserted into the skin on the back of the animal. De-oxygenation and acidosis were induced by lowering the inspiratory oxygen pressure. Oxygenation and heart rate were monitored. A jugular vein cannula was inserted to draw blood samples for analysis of lactate, pH, pco2 , and saturation. Lactate levels in dialysate were compared with plasma lactate levels.

RESULTS

Baseline blood lactate levels were around 1 mmol/L. Upon de-oxygenation, oxygen saturation fell to below 40% for 1 h and blood lactate levels increased 2.5-fold. Correlation of dialysate lactate levels with plasma lactate levels was 0.89 resulting in an R2 of .78 in the corresponding linear regression.

CONCLUSIONS

In this animal model, lactate levels in subcutaneous fluid collected by microdialysis closely reflected blood lactate levels upon transient de-oxygenation, indicating that our device is suitable for subcutaneous measurement of lactate. Microdialysis probe technology allows the measurement of multiple compounds in the dialysate, such as glucose, albumin, or inflammatory mediators, so this technique may offer the unique possibility to shed light on fetal physiology during the intrapartum period.

[Anti-disturbance Fetal Heart Rate System Based on Combined Maternal-fetal Monitoring]

The existing fetal monitor is prone to false detection in the case of high maternal interference in the second stage of labor. With this background, the article designs and implements a combined maternal-fetal fetal heart monitoring system. The system obtains the Doppler signal of the abdominal fetal heart and the blood oxygen signal of the mother's finger, and estimates the maternal interference degree in the fetal heart rate Doppler signal according to the maximum correlation value between the maternal finger blood oxygen signal and the abdominal fetal heart Doppler signal, and switches the fetal heart rate extraction algorithm between the autocorrelation method suitable for lower interference and improved template method suitable for higher interference according to the maternal interference degree. The accuracy of our method is 9.2% which is higher than that of the improved template matching method and 6.1% higher than that of the autocorrelation method.

A Fetal ECG Monitoring System Based on the Android Smartphone

In this paper, a fetal electrocardiogram (ECG) monitoring system based on the Android smartphone was proposed. We designed a portable low-power fetal ECG collector, which collected maternal abdominal ECG signals in real time. The ECG data were sent to a smartphone client via Bluetooth. Smartphone app software was developed based on the Android system. The app integrated the fast fixed-point algorithm for independent component analysis (FastICA) and the sample entropy algorithm, for the sake of real-time extraction of fetal ECG signals from the maternal abdominal ECG signals. The fetal heart rate was computed using the extracted fetal ECG signals. Experimental results showed that the FastICA algorithm can extract a clear fetal ECG, and the sample entropy can correctly determine the channel where the fetal ECG is located. The proposed fetal ECG monitoring system may be feasible for non-invasive, real-time monitoring of fetal ECGs.

Sensors for Fetal Hypoxia and Metabolic Acidosis: A Review

This article reviews existing clinical practices and sensor research undertaken to monitor fetal well-being during labour. Current clinical practices that include fetal heart rate monitoring and fetal scalp blood sampling are shown to be either inadequate or time-consuming. Monitoring of lactate in blood is identified as a potential alternative for intrapartum fetal monitoring due to its ability to distinguish between different types of acidosis. A literature review from a medical and technical perspective is presented to identify the current advancements in the field of lactate sensors for this application. It is concluded that a less invasive and a more continuous monitoring device is required to fulfill the clinical needs of intrapartum fetal monitoring. Potential specifications for such a system are also presented in this paper.

Detection of fetal kicks using body-worn accelerometers during pregnancy: Trade-offs between sensors number and positioning

Monitoring fetal wellbeing is key in modern obstetrics. While fetal movement is routinely used as a proxy to fetal wellbeing, accurate, noninvasive, long-term monitoring of fetal movement is challenging. A few accelerometer-based systems have been developed in the past few years, to tackle common issues in ultrasound measurement and enable remote, self-administrated monitoring of fetal movement during pregnancy. However, many questions remain unanswered to date on the optimal setup in terms of body-worn accelerometers as well as signal processing and machine learning techniques used to detect fetal movement. In this paper, we systematically analyze the trade-offs between sensor number and positioning, the presence of reference accelerometers outside of the abdominal area and provide guidelines on dealing with class imbalance. Using a dataset of 15 measurements collected employing 6 three-axial accelerometers we show that including a reference accelerometer on the back of the participant consistently improves fetal movement detection performance regardless of the number of sensors utilized. We also show that two accelerometers plus a reference accelerometer are sufficient for optimal results.

Examiner's finger-mounted fetal tissue oximetry: a preliminary report on 30 cases

OBJECTIVE

To describe preliminary experience with a finger-mounted fetal tissue oximetry probe during the 2nd stage of labor.

MATERIALS AND METHODS

A total of 30 term pregnant women without pregnancy complications were recruited. We measured fetal tissue oxygen saturation (FtO2) by using a finger-mounted fetal tissue oximetry during cervical examinations in the 2nd stage of labor. The data capturing rate of FtO2 and the interclass correlation coefficient were also examined. The mean FtO2 was compared to the neonatal condition assessed by the levels of umbilical cord blood.

RESULTS

FtO2 was obtained in all cases, regardless of wetness, hair color, the part of the fetal head that was exposed, rotation of the fetus, color of amniotic fluid, and caput succedaneum. The mean FtO2 was 65.5%±8.58% in normal neonates [Apgar score >7 (1 min), n=25]. The mean FtO2 was significantly correlated with umbilical cord arterial pH (r=0.52, P=0.0030, n=30), but not with umbilical cord arterial partial pressure of oxygen. The interclass correlation coefficient was 0.94.

CONCLUSIONS

Tissue oxygen saturation of the fetal head was obtained easily by the examiner's finger-mounted fetal tissue oximetry.

Midwives matter more than monitors

In this column, Sara Wickham takes a sideways look at issues relevant to midwives, students, women and families, inviting us to sit down with a cup of tea and ponder what we think we know. Research has consistently failed to show that electronic fetal monitoring makes a positive difference to women or babies. Yet this technology continues to be used, with some units now using central monitoring systems. This article considers the results of a study showing the effect of these on women's experiences, comparing the value of monitors and midwives.

Can Intrapartum Cardiotocography Predict Uterine Rupture among Women with Prior Caesarean Delivery?: A Population Based Case-Control Study

OBJECTIVE

To compare cardiotocographic abnormalities recorded during labour in women with prior caesarean delivery (CD) and complete uterine rupture with those recorded in controls with prior CD without uterine rupture.

STUDY DESIGN

Women with complete uterine rupture during labour between 1997 and 2008 were identified in the Danish Medical Birth Registry (n = 181). Cases were validated by review of medical records and 53 cases with prior CD, trial of labour, available cardiotocogram (CTG) and complete uterine rupture were included and compared with 43 controls with prior CD, trial of labour and available CTG. The CTG tracings were assessed by 19 independent experts divided into groups of three different experts for each tracing. The assessors were blinded to group, outcome and clinical data. They analyzed occurrence of defined abnormalities and classified the traces as normal, suspicious, pathological or pre-terminal according to international guidelines (FIGO).

RESULTS

A pathological CTG during the first stage of labour was present in 77% of cases and in 53% of the controls (OR 2.58 [CI: 0.96-6.94] P = 0.066). Fetal tachycardia was more frequent in cases with uterine rupture (OR 2.50 [CI: 1.0-6.26] P = 0.053). Significantly more cases showed more than 10 severe variable decelerations compared with controls (OR 22 [CI: 1.54-314.2] P = 0.022). Uterine tachysystole was not correlated with the presence of uterine rupture.

CONCLUSION

A pathological cardiotocogram should lead to particular attention on threatening uterine rupture but cannot be considered a strong predictor as it is common in all women with trial of labour after caesarean delivery.

Feature selection for computerized fetal heart rate analysis using genetic algorithms

During birth, timely and accurate diagnosis is needed in order to prevent severe conditions such as birth asphyxia. The fetal heart rate (FHR) is often monitored during labor to assess the condition of fetal health. Computerized FHR analysis is needed to help clinicians identify abnormal patterns and to intervene when necessary. The objective of this study is to apply Genetic Algorithms (GA) as a feature selection method to select a best feature subset from 64 FHR features and to integrate these best features to recognize unfavorable FHR patterns. The GA was trained on 408 cases and tested on 102 cases (both balanced datasets) using a linear SVM as classifier. 100 best feature subsets were selected according to different splits of data; a committee was formed using these best classifiers to test their classification performance. Fair classification performance was shown on the testing set (Cohen's kappa 0.47, proportion of agreement 73.58%). To our knowledge, this is the first time that a feature selection method has been tested for FHR analysis on a database of this size.

Automated Software Analysis of Fetal Movement Recorded during a Pregnant Woman's Sleep at Home

Fetal movement is an important biological index of fetal well-being. Since 2008, we have been developing an original capacitive acceleration sensor and device that a pregnant woman can easily use to record fetal movement by herself at home during sleep. In this study, we report a newly developed automated software system for analyzing recorded fetal movement. This study will introduce the system and compare its results to those of a manual analysis of the same fetal movement signals (Experiment I). We will also demonstrate an appropriate way to use the system (Experiment II). In Experiment I, fetal movement data reported previously for six pregnant women at 28-38 gestational weeks were used. We evaluated the agreement of the manual and automated analyses for the same 10-sec epochs using prevalence-adjusted bias-adjusted kappa (PABAK) including quantitative indicators for prevalence and bias. The mean PABAK value was 0.83, which can be considered almost perfect. In Experiment II, twelve pregnant women at 24-36 gestational weeks recorded fetal movement at night once every four weeks. Overall, mean fetal movement counts per hour during maternal sleep significantly decreased along with gestational weeks, though individual differences in fetal development were noted. This newly developed automated analysis system can provide important data throughout late pregnancy.

Validation of a point-of-care (POC) lactate testing device for fetal scalp blood sampling during labor: clinical considerations, practicalities and realities

BACKGROUND

Although fetal blood sampling for pH is well established the use of lactate has not been widely adopted. This study validated the performance and utility of a handheld point-of-care (POC) lactate device in comparison with the lactate and pH values obtained by the ABL 800 blood gas analyzer.

METHODS

The clinical performance and influences on accuracy and decision-making criteria were assessed with freshly taken fetal blood scalp samples (n=57) and umbilical cord samples (n=310). Bland-Altman plot was used for data plotting and analyzing the agreement between the two measurement devices and correlation coefficients (R²) were determined using Passing-Bablok regression analysis.

RESULTS

Sample processing errors were much lower in the testing device (22.8% vs. 0.5%). Following a preclinical assessment and calibration offset alignment (0.5 mmol/L) the test POC device showed good correlation with the reference method for lactate FBS (R²=0.977, p<0.0001, 95% CI 0.9 59-0.988), arterial cord blood (R²=0.976, p<0.0001, 95% CI 0.967-0.983) and venous cord blood (R²=0.977, p<0.0001, 95% CI 0.968-0.984).

CONCLUSIONS

A POC device which allows for a calibration adjustment to be made following preclinical testing can provide results that will correlate closely to an incumbent lactate method such as a blood gas analyzer. The use of a POC lactate device can address the impracticality and reality of pH sample collection and testing failures experienced in day to day clinical practice. For the StatStrip Lactate meter we suggest using a lactate cut-off of 5.1 mmol/L for predicting fetal acidosis (pH<7.20).

[A rapid fetal ECG acquisition system based on FT245RL]

A rapid fetal ECG signal acquisition system is designed, which includes three modules: a front-end signal acquisition module, a micro control module and a PC software application module. The first two modules are accomplished through the ADS1294 and the STM32F103 chips, respectively, and the third one is developed in VC++ platform. By using the FT245RL chip, the proposed system implements the serial-parallel conversion communication between ARM and PC, improving the data transmission rate largely. Also, it has a simple structure, with low power consumption and high precision. Furthermore, it can collect fetal ECG signals from mother's abdominal wall and convert them into the 24-bit digital signals.

Suitability of POC lactate methods for fetal and perinatal lactate testing: considerations for accuracy, specificity and decision making criteria

BACKGROUND

Point of care (POC) testing for fetal scalp blood lactate is a more user friendly and more successful approach compared to scalp pH for intrapartum fetal monitoring. The aim of this study was to assess the analytical specificity and clinical reliability of three POC lactate methods.

METHODS

The analytical performance of three POC lactate methods was compared to Cobas 6000 (Roche Diagnostics) laboratory reference method: Lactate Pro from Arkray, GEM 4000 from Instrumentation Laboratory and StatStrip Lactate from Nova Biomedical. The clinical performance and influences on accuracy and decision making criteria for the three POC methods was assessed with umbilical cord samples and compared to the laboratory reference method. The influence of varying ranges of hemoglobin, pH and partial oxygen pressure (pO(2)) on the accuracy of results was assessed.

RESULTS

Although all three POC methods showed good correlation with the reference method for the umbilical cord sample population (r=0.989, 0.973 and 0.980, respectively), Lactate Pro and Gem 4000 showed a significant negative bias compared to the reference method. The degree of bias meant a significant readjustment of decision making criteria was required for fetal lactate use. The accuracy of the Lactate Pro results was affected by hemoglobin and to a lesser extent pH.

CONCLUSIONS

The three electrochemical POC devices can measure fetal lactate reliably. StatStrip Lactate showed a closer correlation and concordance to our laboratory reference method. The results of this study indicate the requirement for predetermining the reliability of POC lactate methods before use present in fetal and perinatal settings.

Fetal electrocardiogram enhancement in abdominal recordings: recording setup analysis

The fetal electrocardiogram (fECG) obtained from the abdominal signals, to monitor the wellbeing of the fetus, is a weak signal, recorded by placing electrodes on the maternal abdomen surface. When recording the abdominal fECG, the main problem is to separate the fECG from the background noise, including the maternal electrocardiogram (mECG) and/or the power line interference (PLI), this leading to an improved fECG signal to noise ratio (SNR). This paper proposes and evaluates three types of recording configurations, having different reference location, and analyzes the performance of each recording setup, based on the corresponding SNRs, quantitatively evaluated. The fECG extraction is carried out in order to evaluate the performance of each proposed configuration.

Estimate of the fetal temperature increase due to UHF RFID exposure

Exposure from electromagnetic (EM) devices has increased during the last decades due to the rapid development of new technologies. Among them, radiofrequency identification (RFID) applications are used in almost every aspect of everyday life, which could expose people unselectively. This scenario could pose potential risks for certain groups of general population, such as pregnant women, who are more sensitive to thermal effects produced by EM exposure. In this paper, the temperature rise at the steady state in two pregnant women models exposed to UHF RFID has been assessed. Results show that heating of tissues is far from the threshold of biological effects indicated by radiation protection guidelines.

Scattering transform for intrapartum fetal heart rate characterization and acidosis detection

Early acidosis detection and asphyxia prediction in intrapartum fetal heart rate is of major concern. This contribution aims at assessing the potential of the Scattering Transform to characterize intrapartum fetal heart rate. Elaborating on discrete wavelet transform, the Scattering Transform performs a non linear and multiscale analysis, thus probing not only the covariance structure of data but also the full dependence structure. Applied to a real database constructed by a French public academic hospital, the Scattering Transform is shown to catch relevant features of intrapartum fetal heart rate time dynamics and to have a satisfactory ability to discriminate Normal subjects from Abnormal.

Reconstruction of fetal vector electrocardiogram from maternal abdominal signals under fetus body rotations

Fetal electrocardiogram (fECG) and its vector form (fVECG) could provide significant clinical information concerning physiological conditions of a fetus. So far various independent component analysis (ICA)-based methods for extracting fECG from maternal abdominal signals have been proposed. Because full extraction of component waves such as P, Q, R, S, and T, is difficult to be realized under noisy and nonstationary situations, the fVECG is further hard to be reconstructed, where different projections of the fetal heart vector are required. In order to reconstruct fVECG, we proposed a novel method for synthesizing different projections of the heart vector, making good use of the fetus movement. This method consists of ICA, estimation of rotation angles of fetus, and synthesis of projections of the heart vector. Through applications to the synthetic and actual data, our method is shown to precisely estimate rotation angle of the fetus and to successfully reconstruct the fVECG.

Vectorcardiographic loop alignment for fetal movement detection using the expectation-maximization algorithm and support vector machines

Reduced fetal movement is an important parameter to assess fetal distress. Currently, no suitable methods are available that can objectively assess fetal movement during pregnancy. Fetal vectorcardiographic (VCG) loop alignment could be such a method. In general, the goal of VCG loop alignment is to correct for motion-induced changes in the VCGs of (multiple) consecutive heartbeats. However, the parameters used for loop alignment also provide information to assess fetal movement. Unfortunately, current methods for VCG loop alignment are not robust against low-quality VCG signals. In this paper, a more robust method for VCG loop alignment is developed that includes a priori information on the loop alignment, yielding a maximum a posteriori loop alignment. Classification, based on movement parameters extracted from the alignment, is subsequently performed using support vector machines, resulting in correct classification of (absence of) fetal movement in about 75% of cases. After additional validation and optimization, this method can possibly be employed for continuous fetal movement monitoring.

Maintaining the passion for pinards

Throughout my midwifery programme I have developed a passion for the use of pinards; a skill that may be lost within midwifery. It is often acknowledged that the use of pinard stethoscopes prior to the use of electronic devices is best practice (Royal College of Midwives (RCM) 2012), yet it is a practice that seems to be losing its place. This article aims to share some of the benefits of using a pinard and encourages the reader to reflect on their own feelings towards using this tool in practice. I will analyse whether or not there is still a value for pinards following an event I experienced whilst on clinical placement. This reflection uses an adapted version of Driscoll's Model of structured reflection (Driscoll 2000).

Telefetalcare: a first prototype of a wearable fetal electrocardiograph

Fetal heart rate monitoring is fundamental to infer information about fetal health state during pregnancy. The cardiotocography (CTG) is the most common antepartum monitoring technique. Abdominal ECG recording represents the most valuable alternative to cardiotocography, as it allows passive, non invasive and long term fetal monitoring. Unluckily fetal ECG has low SNR and needs to be extracted from abdominal recordings using ad hoc algorithms. This work describes a prototype of a wearable fetal ECG electrocardiograph. The system has flat band frequency response between 1-60 Hz and guarantees good signal quality. It was tested on pregnant women between the 30(th) and 34(th) gestational week. Several electrodes configurations were tested, in order to identify the best solution. Implementation of a simple algorithm for FECG extraction permitted the reliable detection of maternal and fetal QRS complexes. The system will allow continuative and deep screening of fetal heart rate, introducing the possibility of home fetal monitoring.

Implantable ultra-low pulmonary pressure monitoring system for fetal surgery

Congenital pulmonary hypoplasia is a devastating condition affecting fetal and newborn pulmonary physiology, resulting in great morbidity and mortality. The fetal lung develops in a fluid-filled environment. In this work, we describe a novel, implantable pressure sensing and recording device which we use to study the pressures present in the fetal pulmonary tree throughout gestation. The system achieves 0.18 cm H2O resolution and can record for twenty one days continuously at 256 Hz. Sample tracings of in vivo fetal lamb recordings are shown.

[Disputes and history of fetal heart monitoring]

The concept of fetal heart monitoring to determine the fetal wellbeing state has been employed for almost 300 years, but in the last 50 years it has observed drastic changes due to the incorporation of the electronic devices that has started controversy since the moment of its description and point of start. The purpose of this article is to mention the key points and controversial moments in the history of the cardiotocography

Application of spatio-temporal filtering to fetal electrocardiogram enhancement

In this paper we propose a new structure of the instrumentation for electrocardiographic fetal monitoring. We apply a single-channel approach to maternal electrocardiogram suppression in the recorded four abdominal bioelectric signals. Then we exploit spatial and temporal properties of the extracted four-channel fetal electrocardiogram to construct a new channel with higher signal-to-noise ratio. Finally, we perform detection of fetal QRS complexes. The proposed approach is investigated with the help of the constructed database of the maternal abdominal signals. During the detection tests, the spatio-temporal filtering allowed us to decrease significantly the number of the detection errors of different detectors applied. Moreover, we present visually that even if the fetal QRS complexes are buried in noise, the spatio-temporal filtering can produce the signal with the discernible ones.

Validation of a trust in medical technology instrument

A patient's trusting attitude towards technology used in their medical care may be a predictor of acceptance or rejection of the technology and, by extension, the physician. The aim of this study was to rigorously determine the validity of an instrument for measuring patients' trust in medical technology. Instrument validity was established based on a framework, which included test and data evidence for validity assessment. The framework for validity assessment evaluates the instrument on content, substantive, structural, generalizability, external and consequential aspects of validity. The results of the current study show that the instrument is reliable and valid for assessing a patient's trust in obstetric medical technology.

Telemedicine fetal phonocardiography surveillance: an italian satisfactory experience

In this paper we describe an Italian experience of fetal home monitor, organized using a portable phonocardiography system (product by Pentavox, Hungary), and the method utilized to evaluate its effectiveness in providing quality services and patient satisfaction. Patient satisfaction is an important dimension in the evaluation of quality care delivery. We used phonocardiography technique in our experience of fetal home monitoring as it is non invasive and passive in nature, low-cost and easy to use. A lightweight portable phonocardiograph (Fetaphon-home) was assigned to six selected patients, without effective pregnancy risk to monitor fetal heartbeat, uterine contractions and fetal movements at home or wherever they need it. The selected patients were instructed by trained personnel in the use of the monitoring device. Patients were asked to perform the recording two times a week and to transmit 20-min signal to the reference centre. The home monitoring sessions were performed in addition to the routine surveillance at a gynecologist's office; thus, the home monitoring did not replace clinic visits. The women were requested to fill a satisfaction questionnaire in order to evaluate their quality of life and anxiety state. Preliminary results have shown that home fetal surveillance appreciably reduces the need of travel for patients and consequently their stress. Furthermore, our results suggest that, after a short training, pregnant women are able to record and transmit long traces without troubles. Use of telemedicine system was generally well accepted by pregnant women since it increased the possibility of fetal long-term home surveillance which in turn could increase the efficiency of the service offered to them.

The need for a new outlook on labor monitoring

Fetal heart rate monitors, including the newer pulse-oximetry and STAN monitors, are designed to detect fetal distress that affects less than 1% of women in labor. Non-progressive labor is a much more common disorder than fetal distress, with approximately 50% of women in labor requiring oxytocin. Current technology assessing labor progress is subjective and inaccurate. There is a need for objective and accurate technology to measure labor progress and the effect it may have on managing labor and, specifically, non-progressive labor.

Integrating a hand held computer and stethoscope into a fetal monitor

This article presents procedures for modifying a hand held computer or personal digital assistant (PDA) into a versatile device functioning as an electronic stethoscope for fetal monitoring. Along with functioning as an electronic stethoscope, a PDA can provide a useful information source for a medical trainee. Feedback from medical students, residents and interns suggests the device is well accepted by medical trainees.

[Design of a novel fuzzy FHR monitor and its applications]

The paper presents a novel fetal heart rate (FHR) detecting system which is a fuzzy counter using the auto-correlation and fuzzy mathematic algorithm. This system is able to deal with the increase and decrease phenomena of FHR, caused by the various interference and noises. It has a higher detection level than ever and a better robust system based on the DSP.

Automatic detection of ultrasonic Doppler signal episodes resulting from fetal breathing movements

A method for automatic detection of fetal breathing movements has been proposed, based on the time-frequency structure of the corresponding continuous wave ultrasonic Doppler signals. The method uses spectral analysis of the envelope of the directional Doppler signal and cross-correlation analysis of both directional envelopes. Detection rule comprises the following criteria: presence of the peak in the envelope spectrum and of the adequate signal level in the frequency range corresponding to the fetal breathing rhythm, the peak value and the position limits of the peak of the cross-correlation coefficient of the both directional envelopes. The effect of the criteria setting on the rule performance and the tradeoff between the specificity and sensitivity was investigated. The rule is most sensitive to the threshold value of the cross-correlation coefficient of the envelopes. The limits of the position of this peak are crucial for the distinction between the breathing episodes and hiccups. The optimal settings of the criteria, resulting in average sensitivity and specificity exceeding, respectively, 0.70 and 0.80, are proposed.

Use of fetal electrocardiogram for intrapartum monitoring

INTRODUCTION

Intrapartum fetal monitoring is essential for the identification of fetal hypoxia to reduce perinatal morbidity and mortality. Cardiotocography is associated with low specificity for fetal acidosis and poor perinatal outcome leading to unnecessary operative deliveries. ST waveform analysis of the fetal electrocardiogram has been shown to be a promising adjunctive intrapartum assessment tool. We aim to present the pathophysiology, the role of intrapartum monitoring and the practical usage of this relatively new technology in our review.

METHODS

An electronic search of Medline and OVID was carried out, followed by a manual search of the references identified by the electronic search.

RESULTS

The incorporation of ST waveform analysis to cardiotocography has been shown to reduce the rates of neonatal metabolic acidosis, moderate and severe neonatal encephalopathy, thus improving perinatal outcome. The reduction in operative delivery rates due to fetal distress is also significant. The pathophysiology and practical usage of this technology were discussed.

CONCLUSIONS

With more accurate identification of fetal hypoxia and reduction of unnecessary intervention rates, incorporation of ST waveform analysis of fetal electrocardiography into cardiotocography can improve the standard of intrapartum fetal monitoring.

Medical devices; obstetrical and gynecological devices; classification of computerized labor monitoring system. Final rule

The Food and Drug Administration (FDA) is classifying the computerized labor monitoring systems into class II (special controls). Elsewhere in this issue of the Federal Register, FDA is announcing the availability of a guidance document entitled, "Guidance for Industry and FDA Staff; Class II Special Controls Guidance Document: Computerized Labor Monitoring Systems," which will serve as the special controls for these devices. The agency is classifying these devices into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of these devices.

The Actifetus system: a multidoppler sensor system for monitoring fetal movements

Fetal heart rate (FHR) monitoring is a crucial part of monitoring at-risk pregnancies and labor. Its aim is to detect any abnormalities that might indicate acute fetal distress and a need for rapid treatment to avoid death or serious sequelae, including cerebral handicap. The use of fetal biophysical profiles in high-risk pregnancies (gravidic hypertension, in utero infection, etc.) helps to distinguish healthy fetuses from those with chronic conditions. Fetal biophysical profile scores have been developed that integrate five biophysical parameters, one of which is derived from the FHR. The major parameters detected are the rate of fetal movements, fetal tone, fetal breathing movement and amniotic fluid volume. All of those parameters except FHR are obtained by prolonged echographic observation and cannot be used routinely. We developed in this study a new multigate multitransducer pulsed Doppler system for survey of fetal behavior. Fast Fourier transform and autocorrelation function have been used for processing and analyzing ultrasonic Doppler signals generated by fetal movements. Several parameters are analyzed in each of the 12 x 5 = 60 Doppler gates: amplitude of signals reflected by moving fetal structures, velocity, direction and amplitude of displacement of fetal structure (heart, chest, limbs). From these parameters it is possible to calculate FHR and characterize fetal activity. Preliminary in vivo results obtained in 15 pregnant women (30 to 36 wk) are very encouraging but they have yet to be confirmed in future studies. These results also demonstrate the advantages of transducers designed for improved fetal movement detection. The algorithms needs to be precise enough to allow the Actifetus system to function in real time. We now have at our disposal some algorithms that succeed in quantifying FHR and fetal movements with a signal from a given sensor at a given depth. This study confirms the feasibility of monitoring fetal movements by the Actifetus system and demonstrates the importance of the characterization of fetal rhythms (and fetal behavior). The Actifetus system will serve as a new mean for studying fetal response to environment and detecting anomalies related to fetal suffering.

Application of the matching pursuit method in a fetal phonocardiographic telemedicine system

A novel compact method for fetal home monitoring optimized for long data acquisition time has already been presented. The method involves preprocessing a disturbed acoustic signal received on the maternal abdomen. The present work summarizes phenomena encountered during analysis of the incoming PCG signal, and describes further improvements made to the analysis system already in use including the application of the MP method to determining heartbeat lengths and identifying murmurs between heart sounds.

STAN, a clinical audit: the outcome of 2 years of regular use in the city of Varberg, Sweden

OBJECTIVE

To monitor and analyze (audit) the introduction of the STAN methodology in a district hospital.

DESIGN

Retrospective study covering the total population of deliveries at term during 2004 and 2005.

MATERIAL AND METHODS

1,875 out of 3,193 term pregnancies (59%) were monitored using the STAN fetal heart monitor (Neoventa Medical, Moelndal, Sweden) and the associated clinical guidelines. Cord metabolic acidosis, neonatal outcome, and rates of operative deliveries for fetal distress were recorded.

RESULTS

The overall cesarean section rate was significantly reduced in the STAN group. Emergency (crash) cesarean sections were significantly reduced from 1.51% to 0.27% in the cardiotocography- and STAN-monitored groups, respectively (OR 0.18, 95% CI 0.07-0.49). When cesarean section was performed only because of non-reassuring cardiotocography, cord acid base was significantly higher, 7.26 versus 7.19 (p<0.01), as compared to when STAN guidelines were followed. Total population rates for operative deliveries for fetal distress and cesarean section rates were 6.7% and 3.5% respectively. The corresponding metabolic acidosis rate was 0.5%.

CONCLUSION

High STAN usage in a busy labor ward setting provided an outcome equaling that noted previously in a larger academic unit, demonstrating the safe implementation of the STAN methodology in a nonacademic unit.

[Design of a wireless fetal electrocardiogram monitoring system based on S3C2410]

This paper introduces a new fetal electrocardiogram monitoring system based on S3C2410 and telecommunication, and its framework and flow chart. Based on the genetic algorithm, the improved IIR adaptive filter achieves the non-invasive, real-time extraction of FECG. The system provides the reliable gist for the diagnosis of fetal congenital diseases. FECG extraction, S3C2410, telecommunication, genetic algorithm, IIR adaptive filter.