Maternal Abdominal Surface Research Articles

Gestational diabetes mellitus early prediction by maternal body fat index: A cohort study

ObjectivesTo compare the performance of maternal body fat index (BFI) assessed during the first 20+6 weeks among 138 pregnant women in an ultrasound outpatient clinic as a predictor of gestational diabetes mellitus (GDM) later in pregnancy. MethodMaternal visceral and subcutaneous fat was measured with a convex ultrasound probe placed in two locations on the maternal abdominal surface: the first in the mid-sagittal epigastric region, visualising epigastric fat, and the second 2cm above the maternal umbilical scar, visualising periumbilical fat. Ultrasound callipers measured the distance from dermal edge to the linea alba and after from the linea alba to the anterior hepatic surface (epigastric fat). Periumbilical fat was measured from the dermal edge to the linea alba and after from the linea alba to the anterior aortic surface. The BFI formula was [visceral adipose tissue (mm)×subcutaneous adipose tissue (mm)]/maternal height (cm). ResultsThe best thresholds for predicting GDM outcome for epigastric and periumbilical BFI were 1.2 and 4.8, respectively. Odds ratio, sensitivity and specificity were 5.88 (95% CI 1.86–18.6), 80.9%, 58.0% for the epigastric site and 6.31 (95% CI 1.73–22.94), 84.2%, 54.2% for the periumbilical site. Pre-pregnancy body mass index compatible with adult obesity shows inadequate predictive performance for GDM outcome. Only epigastric BFI above 1.2 maintained statistical significance for GDM in the logistic regression analysis, when compared to periumbilical BFI above 4.8. ConclusionEpigastric BFI above 1.2 during the first half of pregnancy may help identify women at risk of developing GDM later in pregnancy.

Reminiscence of Fetal Monitoring

Fetal well-being was assessed by enlarging of pregnant abdomen and maternal perception of fetal movements during amenorrhea in old times. There was change to medical monitoring with stethoscopic listening to fetal heart sound after 20 weeks of pregnancy and palpating diagnosis of intrauterine fetus. Recognition of X-ray photo was rarely confirmed fetal position or fetal skeleton under concern on X-ray effect on the fetus. Fetal life was confirmed by appearance of fetal electrocardiogram on maternal limb leads with Seitengalvanometer, then changed to fetal electrocardiogram (FECG) at maternal abdominal surface using electric amplifier. Maeda reported it using handmade amplifier in 1950s. Objective fetal heart sound was also recorded using adult phonocardiographic microphone, transistor amplifier and data recording with slow speed reproduction to trace fetal phonocardiogram (FPCG). As P & T waves of FECG were masked by muscle noises, FPCG was disturbed by systolic murmur in normal pregnancy, and listening to fetal heart beats failed to detect fetal sinusoidal heart rate, the fetal monitoring was changed to fetal heart rate curve recording.

Some regularity on how to locate electrodes for higher fECG SNRs**Project supported by the National Natural Science Foundation of China (Grant No. 61271079) and the Supporting Plan Project of Jiangsu Province, China (Grant No. BE2010720).

The electrocardiogram (ECG) recorded from the abdominal surface of a pregnant woman is a composite of maternal ECG, fetal ECG (fECG) and other noises, while only the fECG component is always needed by us. With different locations of electrode pairs on the maternal abdominal surface to measure fECGs, the signal-to-noise ratios (SNRs) of the recorded abdominal ECGs are also correspondingly different. Some regularity on how to locate electrodes to obtain higher fECG SNRs is needed practically. In this paper, 343 groups of abdominal ECG records were acquired from 78 pregnant women with different electrode pairs locating, and an appropriate extended research database is formed. Then the regularity on fECG SNRs corresponding to different electrode pairs locating was studied. Based on statistical analysis, it is shown that the fECG SNRs are significantly higher in certain locations than others. Reasonable explanation is also provided to the statistical result using the theories of the fetal cardiac electrical axis and the signal phase delay.

A novel approach for phonocardiographic signals processing to make possible fetal heart rate evaluations

In this paper, a non-invasive, portable and inexpensive antenatal care system is developed using fetal phonocardiography. The fPCG technique has the potential to provide low-cost and long-term diagnostics to the under-served population. The fPCG signal contains valuable diagnostic information regarding fetal health during antenatal period. The fPCG signals are acquired from the maternal abdominal surface using a wireless data acquisition and recording system. The diagnostic parameters e.g., baseline, variability, acceleration and deceleration of the fetal heart rate are derived from the fPCG signal. A model based on adaptive neuro-fuzzy inference system is developed for the evaluation of fetal health status. To study the performance of the developed system, experiments were carried out with real fPCG signals under the supervision of medical experts. Its performance is found to be in close proximity with the widely accepted Doppler ultrasound based fetal monitor results. The overall performance shows that the developed system has a long-term monitoring capability with very high performance to cost ratio. The system can be used as first screening tool by the medical practitioners.

Accuracy and Reliability of Fetal Heart Rate Monitoring Using Maternal Abdominal Surface Electrodes

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Signal loss during fetal heart rate monitoring using maternal abdominal surface electrodes between 28 and 42 weeks of pregnancy.

Fetal electrocardiography is one of the methods for monitoring the well-being of the fetus. Signal loss limits the proper interpretation of electrocardiogram traces. The aim of this study was to assess the average signal loss in non-invasive abdominal fetal electrocardiogram (fECG) monitoring using the KOMPOREL fetal monitoring system (ITAM, Zabrze, Poland) in women between 28 and 42week of pregnancy. The results were compared to FIGO (International Federation of Gynaecology and Obstetric) and DGGG (Deutsche Gesellschaft für Gynäkologie und Geburtshilfe e.V.) recommendations concerning fetal heart monitoring. The correlation between fetal ECG signal quality, week of pregnancy and patient BMI was evaluated. 773 pregnant women, hospitalized and diagnosed in the Department of Gynecology and Obstetrics, Wroclaw Medical University, underwent 30min of abdominal fECG recordings using the KOMPOREL fetal monitoring system. The average signal loss in abdominal fECG monitoring in the study group was 32%. FIGO recommendations describe an acceptable fetal signal loss of 20%. In our study, 46% (357/773) of the recordings were up to FIGO standards, with fetal heart rate success rates above 80%. According to DGGG guidelines, with acceptable fetal signal loss of 15%, only 39% (303/773) of the recordings could be assessed as accurate. No correlation between fECG signal quality, week of pregnancy and patient BMI was proved. The average signal loss in abdominal fECG monitoring in our study group was 32%. Low fECG signal quality may constitute apotentially limiting factor of the described fetal heart monitoring system. No relationship between fECG signal quality, week of pregnancy and patient BMI was proved.

Comment on the article “Accuracy and reliability of fetal heart rate monitoring using maternal abdominal surface electrodes”

We found the article by Cohen et al. in the November issue of AOGS, regarding fetal heart function monitoring with electrodes placed on the abdomen of a pregnant woman during labor (fetal electrocardiography), very interesting 1. We are particularly interested in the ratio of cases in which achievement of an electric signal from the fetal heart was successful enough for it to be read, recorded and evaluated; and therefore satisfactory for application of the method for antelabor and intralabor monitoring of the fetal condition. In a study at our center we applied transabdominal monitoring to 612 women between 28 and 42 weeks of gestation in an uncomplicated pregnancy, and in 91 cases of a pregnancy complicated by fetal intrauterine growth restriction or pregnancy-induced hypertension, as well as in 84 cases complicated by imminent preterm delivery. Examinations were performed using the KOMPOREL® system (ITAM, Zabrze, Poland), with an electrode placement scheme almost identical to the scheme applied in the Santa Monica system 2. The mean value of electric signal loss was 32%. This value is comparable with those reported by Cohen et al. and obtained during monitoring on the first stage of delivery, which may be assumed to be similar to the conditions for examination applied by our team. However, in many cases the loss was much more pronounced. From the practical point of view, a loss of fetal heart rate signals in between 20% and 30% of cases, results in a cardiotocography record quality that makes any interpretation of results of the examination impossible. FIGO recommendations mention 20% as an acceptable signal loss 3. In our material we did not find any correlation between the value of signal loss and body mass index of the pregnant women. A slightly better ratio of patients with loss below 20% during the first stage of the delivery has been presented by Reinhard et al.; however, there were only 144 patients included in the study 4. In our opinion, application of transcutaneous fetal electrocardiography as a method of fetal heart rate monitoring may be limited both before and during delivery, because of the impossibility of foreseeing the value of signal loss, which hinders or even makes impossible proper fetal supervision.

Towards computational modelling of the human foetal electrocardiogram: normal sinus rhythm: AV conduction block and re-entrant tachycardia

Introduction: The 10-100 μV foetal electrocardiogram can be recorded from the maternal abdominal surface from ~12 weeks gestational age (WGA), and RR, PR, QR and QT intervals, and T and P wave dispersions extracted. These non-invasive measures provide quantitative information on sino-atrial node pacemaking rate (via RR), propagation times and velocities (via PR, QT), and ventricular action potential duration and its restitution (QT-RR) during foetal normal sinus rhythm. Arrhythmias are observed in b5% of recordings. Methods: The parameters of biophysically detailed models of adult human cardiac cell electrophysiology, based on voltage clamp, immune-histochemical and mRNA expression data were modified, informed by data from the literature on animal foetal tissue and cardiomyocytes derived from human stem cell lines, to reproduce human foetal RR and QT intervals. One dimensional partial differential equation models of SAN, atrial, AVN and ventricular tissue, with lengths from MRI and intercellular coupling informed by PR and QR intervals, were constructed for hearts from 15–40 WGA. Numerical solutions, with zero-flux boundary conditions, were by the explicit Euler method with time and space steps Δt = 0.005 ms and Δx = 0.1 mm. Results: The 1D model at 15, 30 WGA gave NSR intervals RR: 400, 450; QR: 200, 280 ms. Spatially uniform progressive reduction of {gCa,L and gCa, T} slowed the SAN, and led to AV conduction blocks. Self terminating and persistent re-entry with a period of 340–350 ms within a 1-D ring ventricular tissue model. Conclusion: The preliminary 1-D family of models reproduces the observed timings of fECG intervals from 15–40 WGA, the characteristics of development of foetal AV block, and self terminating ventricular tachycardia.

DENOISING OF HEART SOUND SIGNAL USING WAVELET TRANSFORM

This paper presents a novel wavelet-based denoising method using coefficient thresholding technique. The proposed method uses the adaptive thresholding which overcome the shortcomings of discontinuous function in hard-thresholding and also can eliminate the permanent bias in soft-thresholding. The qualitative evaluation of the denoising performance has shown that the proposed method cancels noises more effectively than the other examined techniques. The introduced method can be used as preprocessor stage in all fields of phonocardiography, including the recording of fetal heart sounds on the maternal abdominal surface.

Accuracy and reliability of fetal heart rate monitoring using maternal abdominal surface electrodes

Compare the accuracy and reliability of fetal heart rate identification from maternal abdominal fetal electrocardiogram signals (ECG) and Doppler ultrasound with a fetal scalp electrode. Prospective open method equivalence study. Three urban teaching hospitals in the Northeast United States. 75 women with normal pregnancies in labor at >37 weeks of gestation. Three fetal heart rate detection methods were used simultaneously in 75 parturients. The fetal scalp electrode was the standard against which abdominal fetal ECG and ultrasound were judged. The positive percent agreement with the fetal scalp electrode indicated reliability. Bland-Altman analysis determined accuracy. The confusion rate indicated how frequently the devices tracked the maternal heart rate. Positive percent agreement was 81.7 and 73% for the abdominal fetal ECG and ultrasound, respectively (p = 0.002). The abdominal fetal ECG had a lower root mean square error than ultrasound (5.2 vs. 10.6 bpm, p < 0.001). The confusion rate for ultrasound was 20-fold higher than for abdominal ECG (8.9 vs. 0.4%, respectively, p < 0.001). Compared with the fetal scalp electrode, fetal heart rate detection using abdominal fetal ECG was more reliable and accurate than ultrasound, and abdominal fetal ECG was less likely than ultrasound to display the maternal heart rate in place of the fetal heart rate.

Dual transmission model and related spectral content of the fetal heart sounds

A dual transmission model of the fetal heart sounds is presented in which the properties of the signals received on a sensor, installed on the maternal abdominal surface, depend upon the position of the fetus. For a fetus in the occiput anterior position, the predominant spectral content lies in the frequency band 16–50Hz (“impact” mode), but for a fetus in the occiput posterior position, it lies in the frequency band 80–110Hz (“acoustic” mode). Signal processing comprises digital bandpass filtering, matched filtering, Teager energy operator, autocorrelation, and figure of merit algorithms. The digital filter permits the user to select the frequency band that best conforms to the prevailing signal mode. Clinical tests on twelve patients, with some in the occiput anterior and some in the occiput posterior fetal positions, support the validity of the dual transmission model.

FETAL HEART RATE VARIABILITY ANALYSIS FROM PHONOCARDIOGRAPHIC RECORDINGS

This paper presents an algorithm for classification of fetal health status using fetal heart rate variability (fHRV) analysis through phonocardiography. First, the fetal heart sound signals are acquired from the maternal abdominal surface using a specially developed Bluetooth-based wireless data recording system. Then, fetal heart rate (FHR) traces are derived from these signals. Ten numbers of linear and nonlinear features are extracted from each FHR trace. Finally, the multilayer perceptron (MLP) neural network is used to classify the health status of the fetus. Results show very promising performance toward the prediction of fetal wellbeing on the set of collected fetal heart sound signals. Finally, this work is likely to lead to an automatic screening device with additional potential of predicting fetal wellbeing.

Wavelet-based denoising of fetal phonocardiographic signals

Auscultation is still one of the first basic analytical tools used to evaluate functional state of the fetal heart, as well as the first indicator of fetal well-being. Its modern form is called fetal phonocardiography (fPCG). The fPCG technique is passive and can be used for long-term monitoring. In order to improve the diagnostic capabilities of fPCG, robust signal processing techniques are needed for denoising of the signals. Traditional denoising techniques apply a linear filter to remove the noise and interference from the fPCG signals. These methods have certain limitations for the non-stationary random fPCG signals. In this paper, an improved technique for denoising of fPCG signals is presented. A highly sensitive data recording module is used to acquire the fPCG signals from the maternal abdominal surface. The acquired fPCG signals are decomposed, denoised and reconstructed by utilising Matlab wavelet transform toolbox. The proposed approach improves the signal to noise ratio (SNR) of these signals. The presented technique can be used in preprocessing stage of all fPCG-based fetal monitoring applications.

Time-domain analysis of foetal heart sound signals: a novel approach

Foetal heart sound can be extracted from maternal abdominal surface; the technique is also known as foetal Phonocardiography (fPCG). This work investigates the analysis of foetal heart sound in time domain using a novel signal processing algorithm. An innovative approach is presented for the foetal heart sound acquisition, processing, and time domain representation, which can be used in a portable foetal home monitoring applications. The system has been tested for various real and simulated foetal heart sound signals. The outcome of the process is segmented foetal phonocardiogram along with Foetal Heart Rate (FHR) parameters viz., average FHR, standard deviation of FHR and finally the FHR trace.

Searching for the best model: ambiguity of inverse solutions and application to fetal magnetoencephalography

Fetal brain signals produce weak magnetic fields at the maternal abdominal surface. In the presence of much stronger interference these weak fetal fields are often nearly indistinguishable from noise. Our initial objective was to validate these weak fetal brain fields by demonstrating that they agree with the electromagnetic model of the fetal brain. The fetal brain model is often not known and we have attempted to fit the data to not only the brain source position, orientation and magnitude, but also to the brain model position. Simulation tests of this extended model search on fetal MEG recordings using dipole fit and beamformers revealed a region of ambiguity. The region of ambiguity consists of a family of models which are not distinguishable in the presence of noise, and which exhibit large and comparable SNR when beamformers are used. Unlike the uncertainty of a dipole fit with known model plus noise, this extended ambiguity region yields nearly identical forward solutions, and is only weakly dependent on noise. The ambiguity region is located in a plane defined by the source position, orientation, and the true model centre, and will have a diameter approximately 0.67 of the modelled fetal head diameter. Existence of the ambiguity region allows us to only state that the fetal brain fields do not contradict the electromagnetic model; we can associate them with a family of models belonging to the ambiguity region, but not with any specific model. In addition to providing a level of confidence in the fetal brain signals, the ambiguity region knowledge in combination with beamformers allows detection of undistorted temporal waveforms with improved signal-to-noise ratio, even though the source position cannot be uniquely determined.

The influence of coincidence of fetal and maternal QRS complexes on fetal heart rate reliability

Bioelectrical fetal heart activity being recorded from maternal abdominal surface contains more information than mechanical heart activity measurement based on the Doppler ultrasound signals. However, it requires extraction of fetal electrocardiogram from abdominal signals where the maternal electrocardiogram is dominant. The simplest technique for maternal component suppression is a blanking procedure, which relies upon the replacement of maternal QRS complexes by isoline values. Although, in case of coincidence of fetal and maternal QRS complexes, it causes a loss of information on fetal heart activity. Its influence on determination of fetal heart rate and the variability analysis depends on the sensitivity of the heart-beat detector used. The sensitivity is defined as an ability to detect the incomplete fetal QRS complex. The aim of this work was to evaluate the influence of the maternal electrocardiogram suppression method used on the reliability of FHR signal being calculated.

Dual transmission model of the fetal heart tone

Detection of the fetal heart tone by auscultation is sometimes easy, other times very difficult. In the model proposed here, the level of difficulty depends upon the position of the fetus within the maternal abdomen. If the fetus lies in the classical left/right occiput anterior position (head down, back against the maternal abdominal wall), detection by a sensor or stethoscope on the maternal abdominal surface is easy. In this mode, named here the ‘‘direct contact’’ mode, the heartbeat pushes the fetus against the detecting sensor. The motion generates pressure by impact and does not involve acoustic propagation at all. If the fetus lies in a persistent occiput posterior position (spine-to-spine, fetus facing forward), detection is difficult. In this, the ‘‘fluid propagation’’ mode, sound generated by the fetal heart and propagating across the amniotic fluid produces extremely weak signals at the maternal surface, typically 30 dB lower than those of the direct contact mode. This reduction in tone level can be compensated by judicious selection of detection frequency band and by exploiting the difference between the background noise levels of the two modes. Experimental clinical results, demonstrating the tones associated with the two respective modes, will be presented.

An advanced method in fetal phonocardiography

The long-term variability of the fetal heart rate (FHR) provides valuable information on the fetal health status. The routine clinical FHR measurements are usually carried out by the means of ultrasound cardiography. Although the frequent FHR monitoring is recommendable, the high quality ultrasound devices are so expensive that they are not available for home care use. The passive and fully non-invasive acoustic recording called phonocardiography, provides an alternative low-cost measurement method. Unfortunately, the acoustic signal recorded on the maternal abdominal surface is heavily loaded by noise, thus the determination of the FHR raises serious signal processing issues. The development of an accurate and robust fetal phonocardiograph has been since long researched. This paper presents a novel two-channel phonocardiographic device and an advanced signal processing method for determination of the FHR. The developed system provided 83% accuracy compared to the simultaneously recorded reference ultrasound measurements.

Analysis of Fetal Heart Activity by the Means of Phonocardiography

This paper presents a novel method for the determination of the fetal heart rate by the means of phonocardiography. The two-channel acoustic recording method measures simultaneously the fetal heart sounds on the maternal abdominal surface with the environmental noises. The recorded signals are sampled and analysed by a personal computer. The proposed measurement and signal processing methods provide an accuracy which is comparable to that of ultrasound technology has. The introduced system is viable as a fully non-invasive and inexpensive portable fetal heart rate monitoring device, especially in the field of home care and telemedicine applications.

Investigation of nonlinear ECoG changes during spontaneous sleep state changes and cortical arousal in fetal sheep.

We examined the processes of cortical activation and deactivation of the fetal brain during spontaneous sleep state transitions and during central nervous processing of vibroacoustic stimulations (VASs) using nonlinear analysis of the electrocorticogram (ECoG). Tests of nonlinearity and a random shuffling routine revealed deterministic and nonlinear portions in the fetal ECoG. As common nonlinear measures are not applicable to nonstationary time series, we developed an algorithm to estimate the predictability of the ECoG in its time course by means of a point prediction error (PPE). The ECoG was recorded before and during VAS from the maternal abdominal surface in seven chronically instrumented fetal sheep at 0.8 of gestation. The PPE during REM sleep was significantly higher than during NREM sleep. VAS in NREM sleep resulted in an abrupt increase of the PPE not reaching the level of REM sleep. The steep increase of the PPE at onset and its slow decrease after cessation of the stimulus were very similar to the dynamics of spontaneous sleep state transitions, suggesting the involvement of the same cortical activating mechanisms. In conclusion, the stage and the time course of fetal brain activation and deactivation patterns can be clearly shown by PPE techniques. The PPE is a useful complement to spectral analysis. Both techniques describe different properties of the ECoG.