The quality of intrapartum fetal heart rate monitoring

Rapid detection of fetal compromise using input length invariant deep learning on fetal heart rate signals

Standard clinical practice to assess fetal well-being during labour utilises monitoring of the fetal heart rate (FHR) using cardiotocography. However, visual evaluation of FHR signals can result in subjective interpretations leading to inter and intra-observer disagreement. Therefore, recent studies have proposed deep-learning-based methods to interpret FHR signals and detect fetal compromise. These methods have typically focused on evaluating fixed-length FHR segments at the conclusion of labour, leaving little time for clinicians to intervene. In this study, we propose a novel FHR evaluation method using an input length invariant deep learning model (FHR-LINet) to progressively evaluate FHR as labour progresses and achieve rapid detection of fetal compromise. Using our FHR-LINet model, we obtained approximately 25% reduction in the time taken to detect fetal compromise compared to the state-of-the-art multimodal convolutional neural network while achieving 27.5%, 45.0%, 56.5% and 65.0% mean true positive rate at 5%, 10%, 15% and 20% false positive rate respectively. A diagnostic system based on our approach could potentially enable earlier intervention for fetal compromise and improve clinical outcomes.

A deep learning framework for noninvasive fetal ECG signal extraction

Introduction: The availability of proactive techniques for health monitoring is essential to reducing fetal mortality and avoiding complications in fetal wellbeing. In harsh circumstances such as pandemics, earthquakes, and low-resource settings, the incompetence of many healthcare systems worldwide in providing essential services, especially for pregnant women, is critical. Being able to continuously monitor the fetus in hospitals and homes in a direct and fast manner is very important in such conditions. Methods: Monitoring the health of the baby can potentially be accomplished through the computation of vital bio-signal measures using a clear fetal electrocardiogram (ECG) signal. The aim of this study is to develop a framework to detect and identify the R-peaks of the fetal ECG directly from a 12 channel abdominal composite signal. Thus, signals were recorded noninvasively from 70 pregnant (healthy and with health conditions) women with no records of fetal abnormalities. The proposed model employs a recurrent neural network architecture to robustly detect the fetal ECG R-peaks. Results: To test the proposed framework, we performed both subject-dependent (5-fold cross-validation) and independent (leave-one-subject-out) tests. The proposed framework achieved average accuracy values of 94.2% and 88.8%, respectively. More specifically, the leave-one-subject-out test accuracy was 86.7% during the challenging period of vernix caseosa layer formation. Furthermore, we computed the fetal heart rate from the detected R-peaks, and the demonstrated results highlight the robustness of the proposed framework. Discussion: This work has the potential to cater to the critical industry of maternal and fetal healthcare as well as advance related applications.

Fetal Heart Rate Preprocessing Techniques: A Scoping Review

Monitoring fetal heart rate (FHR) through cardiotocography is crucial for the early diagnosis of fetal distress situations, necessitating prompt obstetrical intervention. However, FHR signals are often marred by various contaminants, making preprocessing techniques essential for accurate analysis. This scoping review, following PRISMA-ScR guidelines, describes the preprocessing methods in original research articles on human FHR (or beat-to-beat intervals) signal preprocessing from PubMed and Web of Science, published from their inception up to May 2021. From the 322 unique articles identified, 54 were included, from which prevalent preprocessing approaches were identified, primarily focusing on the detection and correction of poor signal quality events. Detection usually entailed analyzing deviations from neighboring samples, whereas correction often relied on interpolation techniques. It was also noted that there is a lack of consensus regarding the definition of missing samples, outliers, and artifacts. Trends indicate a surge in research interest in the decade 2011-2021. This review underscores the need for standardizing FHR signal preprocessing techniques to enhance diagnostic accuracy. Future work should focus on applying and evaluating these methods across FHR databases aiming to assess their effectiveness and propose improvements.

Intrapartum cardiotocography with simultaneous maternal heart rate registration improves neonatal outcome

BACKGROUND

Intrapartum cardiotocographic monitoring of fetal heart rate by abdominal external ultrasound transducer without simultaneous maternal heart rate recording has been associated with increased risk of early neonatal death and other asphyxia-related neonatal outcomes. It is unclear, however, whether this increase in risk is independently associated with fetal surveillance method or is attributable to other factors.

OBJECTIVE

This study aimed to compare different fetal surveillance methods and their association with adverse short- and long-term fetal and neonatal outcomes in a large retrospective cohort of spontaneous term deliveries.

STUDY DESIGN

Fetal heart rate and maternal heart rate patterns were recorded by cardiotocography during labor in spontaneous term singleton cephalic vaginal deliveries in the Hospital District of Helsinki and Uusimaa, Finland between October 1, 2005, and September 30, 2023. According to the method of cardiotocography monitoring at birth, the cohort was divided into the following 3 groups: women with ultrasound transducer, women with both ultrasound transducer and maternal heart rate transducer, and women with internal fetal scalp electrode. Umbilical artery pH and base excess values, low 1- and 5-minute Apgar scores, need for intubation and resuscitation, neonatal intensive care unit admission for asphyxia, neonatal encephalopathy, and early neonatal death were used as outcome variables.

RESULTS

Among the 213,798 deliveries that met the inclusion criteria, the monitoring type was external ultrasound transducer in 81,559 (38.1%), both external ultrasound transducer and maternal heart rate recording in 62,268 (29.1%), and fetal scalp electrode in 69,971 (32.7%) cases, respectively. The rates of both neonatal encephalopathy (odds ratio, 1.48; 95% confidence interval, 1.08-2.02) and severe acidemia (umbilical artery pH <7.00 and/or umbilical artery base excess ≤-12.0 mmol/L) (odds ratio, 2.03; 95% confidence interval, 1.65-2.50) were higher in fetuses of women with ultrasound transducer alone compared with those of women with concurrent external fetal and maternal heart rate recording. Monitoring with ultrasound transducer alone was also associated with increased risk of neonatal intubation for resuscitation (odds ratio, 1.22; 95% confidence interval, 1.03-1.44). A greater risk of severe neonatal acidemia was observed both in the ultrasound transducer (odds ratio, 2.78; 95% confidence interval, 2.23-3.48) and concurrent ultrasound transducer and maternal heart rate recording (odds ratio, 1.37; 95% confidence interval, 1.05-1.78) groups compared with those monitored with fetal scalp electrodes. No difference in risk of neonatal encephalopathy was found between newborns monitored with concurrent ultrasound transducer and maternal heart rate recording and those monitored with fetal scalp electrodes.

CONCLUSION

The use of external ultrasound transducer monitoring of fetal heart rate without simultaneous maternal heart rate recording is associated with higher rates of neonatal encephalopathy and severe neonatal acidemia. We suggest that either external fetal heart rate monitoring with concurrent maternal heart rate recording or internal fetal scalp electrode be used routinely as a fetal surveillance tool in term deliveries.

A Robust Approach Assisted by Signal Quality Assessment for Fetal Heart Rate Estimation from Doppler Ultrasound Signal

Fetal heart rate (FHR) monitoring, typically using Doppler ultrasound (DUS) signals, is an important technique for assessing fetal health. In this work, we develop a robust DUS-based FHR estimation approach complemented by DUS signal quality assessment (SQA) based on unsupervised representation learning in response to the drawbacks of previous DUS-based FHR estimation and DUS SQA methods. We improve the existing FHR estimation algorithm based on the autocorrelation function (ACF), which is the most widely used method for estimating FHR from DUS signals. Short-time Fourier transform (STFT) serves as a signal pre-processing technique that allows the extraction of both temporal and spectral information. In addition, we utilize double ACF calculations, employing the first one to determine an appropriate window size and the second one to estimate the FHR within changing windows. This approach enhances the robustness and adaptability of the algorithm. Furthermore, we tackle the challenge of low-quality signals impacting FHR estimation by introducing a DUS SQA method based on unsupervised representation learning. We employ a variational autoencoder (VAE) to train representations of pre-processed fetal DUS data and aggregate them into a signal quality index (SQI) using a self-organizing map (SOM). By incorporating the SQI and Kalman filter (KF), we refine the estimated FHRs, minimizing errors in the estimation process. Experimental results demonstrate that our proposed approach outperforms conventional methods in terms of accuracy and robustness.

Computerised Cardiotocography Analysis for the Automated Detection of Fetal Compromise during Labour: A Review

The measurement and analysis of fetal heart rate (FHR) and uterine contraction (UC) patterns, known as cardiotocography (CTG), is a key technology for detecting fetal compromise during labour. This technology is commonly used by clinicians to make decisions on the mode of delivery to minimise adverse outcomes. A range of computerised CTG analysis techniques have been proposed to overcome the limitations of manual clinician interpretation. While these automated techniques can potentially improve patient outcomes, their adoption into clinical practice remains limited. This review provides an overview of current FHR and UC monitoring technologies, public and private CTG datasets, pre-processing steps, and classification algorithms used in automated approaches for fetal compromise detection. It aims to highlight challenges inhibiting the translation of automated CTG analysis methods from research to clinical application and provide recommendations to overcome them.

The Effect of Fetal Heart Rate Segment Selection on Deep Learning Models for Fetal Compromise Detection

Monitoring the fetal heart rate (FHR) is common practice in obstetric care to assess the risk of fetal compromise. Unfortunately, human interpretation of FHR recordings is subject to inter-observer variability with high false positive rates. To improve the performance of fetal compromise detection, deep learning methods have been proposed to automatically interpret FHR recordings. However, existing deep learning methods typically analyse a fixed-length segment of the FHR recording after removing signal gaps, where the influence of this segment selection process has not been comprehensively assessed. In this work, we develop a novel input length invariant deep learning model to determine the effect of FHR segment selection for detecting fetal compromise. Using this model, we perform five times repeated five-fold cross-validation on an open-access database of 552 FHR recordings and assess model performance for FHR segment lengths between 15 and 60 minutes. We show that the performance after removing signal gaps improves with increasing segment length from 15 minutes (AUC = 0.50) to 60 minutes (AUC = 0.74). Additionally, we demonstrate that using FHR segments without removing signal gaps achieves superior performance across signal lengths from 15 minutes (AUC = 0.68) to 60 minutes (AUC = 0.76). These results show that future works should carefully consider FHR segment selection and that removing signal gaps might contribute to the loss of valuable information.

Quality of fetal heart rate monitoring with transabdominal fetal ECG during maternal movement in labor: A prospective study

INTRODUCTION

Transabdominal electrocardiographic (TAfECG) acquisition of fetal heart rate (FHR) signals has recently been introduced into leading commercial cardiotocographic (CTG) monitors. Continuous wireless transmission of signals has raised the possibility of the technology being used during maternal mobilization in labor. This study aims to evaluate signal quality and accuracy of TAfECG acquisition of FHR signals during static and active maternal positions in labor when compared with Doppler signals and with the gold-standard method of fetal scalp electrode (FSE).

MATERIAL AND METHODS

A total of 76 women with singleton term pregnancies in the active first stage of labor had simultaneously acquired FHR with TAfECG, Doppler, and FSE. Participants were asked to complete a supervised mobilization scheme, comprising five sequential 10-min periods of lying down, standing, sitting, walking, and rocking on the birthing ball. The three FHR signals were compared, defining signal loss as the percentage of signals under 20 bpm or exceeding 250 bpm and accuracy as the difference with FSE values. Computer analysis was used to quantify variability, accelerations, and decelerations. Static labor positions (lying down, standing, and sitting) were compared with active labor positions (walking and rocking on the birthing ball).

RESULTS

Average signal loss was 5.3% with TAfECG (3.2% in static and 7.4% in active positions) and 15.5% with Doppler (8.3% in static and 30.7% in active positions). Average accuracy was 3.5 bpm with TAfECG (1.9 bpm in static and 5.04 bpm in active positions) and 13.9 bpm with Doppler (3.2 bpm in static and 24.7 bpm in active positions). Average variability was similar with TAfECG and FSE in static positions but significantly higher with TAfECG in active positions (23.6 vs. 13.5 bpm, p < 0.001).

CONCLUSIONS

In static labor positions, TAfECG provides a low signal loss, similar to that obtained with FSE, and a good signal accuracy, so the technique can be considered reliable when the mother is lying down, standing, or sitting. During maternal movement, TAfECG causes an artificial increase in FHR variability, which can cause false reassurance regarding fetal oxygenation. Doppler signals are unreliable during maternal movements.

The quality of intrapartum cardiotocography in preterm labour

OBJECTIVES

The aim of this study is to determine the quality of the foetal heart rate (FHR) recording, defined as signal loss, during preterm labour below 28 weeks gestational age (GA) and contribute to the discussion if cardiotocography (CTG) is of value for the extreme preterm foetus.

METHODS

From January 2010 to December 2019 a retrospective study was conducted with data of 95 FHR recordings of singletons born between 24 and 28 weeks GA at the Amsterdam University Medical Centre, location VUmc. FHR tracings had a duration of at least 30 min and were obtained via external ultrasound mode. Data of all recordings were divided in two groups according to gestation (24-26 weeks and 26-28 weeks). Signal loss was analysed. Statistical significance was calculated by non-parametric tests and chi-square tests. The median signal loss and the proportion of cases exceeding the International Federation of Gynaecology and Obstetrics Guidelines (FIGO) threshold of 20% signal loss were calculated.

RESULTS

One-third of the recordings exceeded the 20% FIGO-criterion for adequate signal quality during the first stage of labour. In the second stage, this was nearly 75%. Similarly, the median signal loss was 13% during the first and 30% during the second stage of labour (p<0.01).

CONCLUSIONS

The quality of FHR monitoring in the extreme preterm foetus is inadequate in a large proportion of the foetuses, especially during the second stage. FHR monitoring is therefore controversial and should be used with caution.

Interpretation of Fetal Heart Rate Monitoring in the Clinical Context

Use of intrapartum fetal heart rate (FHR) monitoring has had limited success in preventing hypoxic injury to neonates. One of the most common limitations of FHR interpretation is the failure to consider chronic and acute clinical factors that may increase the risk of evolving acidemia. This manuscript reviews common clinical factors that may affect the FHR and should be considered when determining the need for early intervention based on changes in the FHR.

Reconstruction of missing samples in antepartum and intrapartum FHR measurements via mini-batch-based minimized sparse dictionary learning

Fetal Heart Rate(FHR), an important recording in Cardiotocography(CTG)-based fetal health status monitoring, is the only information that clinical obstetricians can directly obtain and use. A challenge, however, is that missing samples are very common in FHR due to various causes such as fetal movements and sensor malfunctions. The aim is the development of an inpainting tool which is suitable for different missing lengths q and various total missing percentages Q, as well as for use in online mode. This study focused on two major impediments to existing inpainting methods: the longer the missing length, the more difficult it is to recover with mathematical methods; the reliance on tens of thousands of training samples, and the computational burden caused by full batch-based dictionary learning algorithms. We present a regularized minimization approach to signal recovery, which combines a L0.6-norm minimized sparse dictionary learning algorithm (MSDL) and a model optimization strategy for using a mini-batch version for signal recovery. Using 100 FHR recordings with 2 protocols designed to simulate missing clinical data scenarios, the combined method performed favorably in terms of 5 data analysis metrics and 3 clinical indicators. Comparing 4 inpainting methods, we were able to prove the superiority of the proposed algorithm for both large q and large Q. The experimental results showed the lowest values (2.64 (MAE), 4.68 (RMSE)) when Q=5% with short interval lengths. The developed architecture provides a reference value for the practical application of recovering missing samples online.

The Noninvasive Fetal Electrocardiogram During Labor: A Review of the Literature

Importance

The introduction of the cardiotocogram (CTG) during labor has not been found to improve neonatal outcome. The search for a more reliable, less invasive, and patient-friendly technique is ongoing. The noninvasive fetal electrocardiogram (NI-fECG) has been proposed as one such alternative.

Objectives

The aim of this study was to review the literature on the performance of NI-fECG for fetal monitoring during labor. Following the PRISMA guidelines, a systematic search in MEDLINE, EMBASE, and Cochrane Library was performed. Studies involving original research investigating the performance of NI-fECG during labor were included. Animal studies and articles in languages other than English, Dutch, or German were excluded. The QUADAS-2 checklist was used for quality assessment. A descriptive analysis of the results is provided.

Results

Eight articles were included. Pooled analysis of the results of the separate studies was not possible due to heterogeneity. All studies demonstrate that it is possible to apply NI-fECG during labor. Compared with Doppler ultrasound, NI-fECG performs equal or better in most studies.

Conclusions and Relevance

NI-fECG for fetal monitoring is a promising noninvasive and patient-friendly technique that provides accurate information. Future studies should focus on signal quality throughout labor, with the aim to further optimize technical development of NI-fECG.

A review of fetal cardiac monitoring, with a focus on low- and middle-income countries

There is limited evidence regarding the utility of fetal monitoring during pregnancy, particularly during labor and delivery. Developed countries rely on consensus ‘best practices’ of obstetrics and gynecology professional societies to guide their protocols and policies. Protocols are often driven by the desire to be as safe as possible and avoid litigation, regardless of the cost of downstream treatment. In high-resource settings, there may be a justification for this approach. In low-resource settings, in particular, interventions can be costly and lead to adverse outcomes in subsequent pregnancies. Therefore, it is essential to consider the evidence and cost of different fetal monitoring approaches, particularly in the context of treatment and care in low-to-middle income countries.

This article reviews the standard methods used for fetal monitoring, with particular emphasis on fetal cardiac assessment, which is a reliable indicator of fetal well-being. An overview of fetal monitoring practices in low-to-middle income counties, including perinatal care access challenges, is also presented. Finally, an overview of how mobile technology may help reduce barriers to perinatal care access in low-resource settings is provided.

Evaluation of an external fetal electrocardiogram monitoring system: a randomized controlled trial

OBJECTIVE

The objective of the study was to compare interpretability of 2 intrapartum abdominal fetal heart rate-monitoring strategies. We hypothesized that an external fetal electrocardiography monitoring system, a newer technology using wireless abdominal pads, would generate more interpretable fetal heart rate data compared with standard external Doppler fetal heart rate monitoring (standard external monitoring).

STUDY DESIGN

We conducted a randomized controlled trial at 4 Utah hospitals. Patients were enrolled at labor admission and randomized in blocks based on body mass index to fetal electrocardiography or standard external monitoring. Two reviewers, blinded to study allocation, reviewed each fetal heart rate tracing. The primary outcome was the percentage of interpretable minutes of fetal heart rate tracing. An interpretable minute was defined as >25% fetal heart rate data present and no more than 25% continuous missing fetal heart rate data or artifact present. Secondary outcomes included the percentage of interpretable minutes of fetal heart rate tracing obtained while on study device only, the number of device adjustments required intrapartum, clinical outcomes, and patient/provider device satisfaction. We determined that 100 patients per arm (200 total) would be needed to detect a 5% difference in interpretability with 95% power.

RESULTS

A total of 218 women were randomized, 108 to fetal electrocardiography and 110 to standard external monitoring. Device setup failure occurred more often in the fetal electrocardiography group (7.5% [8 of 107] vs 0% [0 of 109] for standard external monitoring). There were no differences in the percentage of interpretable tracing between the 2 groups. However, fetal electrocardiography produced more interpretable fetal heart rate tracing in subjects with a body mass index ≥30 kg/m². When considering the percentage of interpretable minutes of fetal heart rate tracing while on study device only, fetal electrocardiography outperformed standard external monitoring for all subjects, regardless of maternal body mass index. Maternal demographics and clinical outcomes were similar between arms. In the fetal electrocardiography group, more device changes occurred compared with standard external monitoring (51% vs 39%), but there were fewer nursing device adjustments (2.9 vs 6.2 mean adjustments intrapartum, P < .01). There were no differences in physician device satisfaction scores between groups, but fetal electrocardiography generated higher patient satisfaction scores.

CONCLUSION

Fetal electrocardiography performed similarly to standard external monitoring when considering percentage of interpretable tracing generated in labor. Furthermore, patients reported overall greater satisfaction with fetal electrocardiography in labor. Fetal electrocardiography may be particularly useful in patients with a body mass index ≥30 kg/m².

Doppler Ultrasound Technology for Fetal Heart Rate Monitoring: A Review

Fetal well-being is commonly assessed by monitoring the fetal heart rate (fHR). In clinical practice, the de facto standard technology for fHR monitoring is based on the Doppler ultrasound (US). Continuous monitoring of the fHR before and during labor is performed using a US transducer fixed on the maternal abdomen. The continuous fHR monitoring, together with simultaneous monitoring of the uterine activity, is referred to as cardiotocography (CTG). In contrast, for intermittent measurements of the fHR, a handheld Doppler US transducer is typically used. In this article, the technology of Doppler US for continuous fHR monitoring and intermittent fHR measurements is described, with emphasis on fHR monitoring for CTG. Special attention is dedicated to the measurement environment, which includes the clinical setting in which fHR monitoring is commonly performed. In addition, to understand the signal content of acquired Doppler US signals, the anatomy and physiology of the fetal heart and the surrounding maternal abdomen are described. The challenges encountered in these measurements have led to different technological strategies, which are presented and critically discussed, with a focus on the US transducer geometry, Doppler signal processing, and fHR extraction methods.

A systematic review of cardiac time intervals utilising non-invasive fetal electrocardiogram in normal fetuses

BACKGROUND

Non-invasive fetal electrocardiogram (NIFECG) is an evolving technology in fetal surveillance which is attracting increasing research interest. There is however, only limited data outlining the reference ranges for normal cardiac time intervals (CTIs). The objective of our group was to carry out a systematic review to outline normal fetal CTIs using NIFECG.

METHODS

A systematic review of peer reviewed literature was performed, searching PUBMED,Ovid MEDLINE and EMBASE. The outcomes of interest included fetal CTIs (P wave duration, PR interval, QRS duration and QT interval) and a descriptive summary of relevant studies as well. The outcomes were grouped as early pre-term (≤ 32 weeks), moderate to late pre-term (32-37 weeks) and term (37-41 weeks).

RESULTS

8 studies were identified as suitable for inclusion. Reference ranges of CTIs were generated. Both PR interval and QRS duration demonstrated a linear correlation with advancing gestation. Several studies also demonstrated a reduction in signal acquisition between 27 and 32 weeks due to the attenuation by vernix caseosa. In this group, both the P wave and T waves were difficult to detect due to signal strength and interference.

CONCLUSION

NIFECG demonstrates utility to quantify CTIs in the fetus, particularly at advanced gestations. Larger prospective studies should be directed towards establishing reliable CTIs across various gestations.

Maternal heart rate patterns under resting conditions in late pregnancy

Objectives:

To describe maternal heart rate patterns observed during antenatal monitoring under resting conditions between the gestational ages of 34 to 38 weeks and to demonstrate its associations with uterine activity.

Methods:

Each participant had five high quality ECG electrodes attached to her anterior abdominal wall which were connected to the Monica AN24 device to collect raw electrical signals from the maternal and fetal ECG and signals of uterine activity. Proprietary software was then used to download the raw data and extract the maternal and fetal heart rate patterns and uterine activity.

Results:

Several distinct maternal heart rate patterns were observed. These included unusually high or low levels of variability, tachycardia, bradycardia, regular and irregular periodic changes and sporadic changes where the heart rate suddenly decreased or increased. Some of the fluctuations, especially decelerations of maternal heart rate, seemed to be associated with uterine activity.

Conclusion:

The clinical implications of these different patterns, for both the mother and fetus, needs to be explored further. There is a need for computerized analyses of the different maternal patterns during different gestational ages to determine its relevance.

Synopsis

Various maternal heart rate patterns under resting conditions in late pregnancy are described.

Monitoring Fetal Heart Rate during Labor: A Comparison of Three Methods

The purpose of the study was to compare the accuracy of a noninvasive fetal heart rate monitor with that of ultrasound, using a fetal scalp electrode as the gold standard, in laboring women of varying body habitus, throughout labor and delivery. Laboring women requiring fetal scalp electrode were monitored simultaneously with the investigational device (noninvasive fetal ECG), ultrasound, and fetal scalp electrode. An algorithm extracted the fetal heart rate from the noninvasive fetal ECG signal. Each noninvasive device recording was compared with fetal scalp electrode with regard to reliability by positive percent agreement and accuracy by root mean squared error. Seventy-one women were included in this analysis. Positive percent agreement was 83.4 ± 15.4% for noninvasive fetal ECG and 62.4 ± 26.7% for ultrasound. The root mean squared error compared with fetal scalp electrode-derived fetal heart rate was 4.8 ± 2.0 bpm for noninvasive fetal ECG and 14.3 ± 8.2 bpm for ultrasound. The superiority of noninvasive fetal ECG was maintained for stages 1 and 2 of labor and increases in body mass index. Compared with fetal scalp electrode-derived fetal heart rate, noninvasive fetal ECG is more accurate and reliable than ultrasound for intrapartum monitoring for stages 1 and 2 of labor and is less affected by increasing maternal body mass index. This confirms the results of other workers in this field.

Effect of maternal position and uterine activity on periodic maternal heart rate changes before elective cesarean section at term

INTRODUCTION

Because little is known about the effects of maternal position on periodic changes in the maternal heart rate (MHR) in late pregnancy, a prospective observational study was done at Tygerberg Academic Hospital in Cape Town. Pregnant women admitted for elective cesarean section were studied to determine the effect of changes in position on the maternal and fetal heart rates (FHR) and maternal blood pressure.

MATERIAL AND METHODS

Continuous transabdominal non-invasive recording of MHR, FHR patterns and uterine activity was done for 1 h in 119 women, using the AN24 device from Monica Health Care. Maternal position was changed every 15 min from lateral to supine, then to the other lateral position and finally supine again. Blood pressure was measured in the left arm and left lower leg three times during each 15-min period.

RESULTS

MHRs were four beats per minute slower in the left lateral position than in the right lateral position. Periodic MHR changes were seen in 13 (10.9%) women. Most of these (84.6%) were associated with uterine activity and not with maternal position. No changes in FHR patterns were observed after position changes.

CONCLUSIONS

In a subgroup of pregnant women at term, uterine activity was associated with periodic decelerations of the MHR. In low risk pregnancies there seems to be no effect on the FHR pattern. Implications for the compromised fetus have not yet been investigated.

Fetal optimization during maternal sepsis: relevance and response of the obstetric anesthesiologist

PURPOSE OF REVIEW

In many labor and delivery units, the obstetric anesthesiologist is often responsible for managing and stabilizing the acutely septic parturient. The management of maternal sepsis has been summarized previously; this study will focus on the implications of maternal sepsis on the fetus, and ways to optimize fetal outcomes.

RECENT FINDINGS

Although the complex pathophysiology of sepsis is being better understood, the incidence of maternal severe sepsis and deaths continues to increase. The differential sensitivities of systemic and uterine vasculature to catecholamines during pregnancy and the role of fetal inflammatory responses have recently been further elucidated. Additional investigations on methods of fetal monitoring are needed to assist in early identification of the compromised fetus. Despite decades of research, management of a septic parturient and her fetus, including the most appropriate resuscitation fluids, vasopressors and hemodynamic monitoring systems to maximize maternal and fetal outcomes, remain controversial.

SUMMARY

In the setting of maternal sepsis, fetal optimization is frequently best accomplished by meeting maternal hemodynamic, oxygenization, and infection treatment goals. Understanding the circulatory and pathophysiologic changes that occur within the uteroplacental unit and fetus is essential to identifying and resolving potential conflicts between maternal and fetal management goals.

A critical appraisal of the evidence for using cardiotocography plus ECG ST interval analysis for fetal surveillance in labor. Part I: the randomized controlled trials

We reappraised the five randomized controlled trials that compared cardiotocography plus ECG ST interval analysis (CTG+ST) vs. cardiotocography. The numbers enrolled ranged from 5681 (Dutch randomized controlled trial) to 799 (French randomized controlled trial). The Swedish randomized controlled trial (n = 5049) was the only trial adequately powered to show a difference in metabolic acidosis, and the Plymouth randomized controlled trial (n = 2434) was only powered to show a difference in operative delivery for fetal distress. There were considerable differences in study design: the French randomized controlled trial used different inclusion criteria, and the Finnish randomized controlled trial (n = 1483) used a different metabolic acidosis definition. In the CTG+ST study arms, the larger Plymouth, Swedish and Dutch trials showed lower operative delivery and metabolic acidosis rates, whereas the smaller Finnish and French trials showed minor differences in operative delivery and higher metabolic acidosis rates. We conclude that the differences in outcomes are likely due to the considerable differences in study design and size. This will enhance heterogeneity effects in any subsequent meta-analysis.

Influence of maternal body mass index on accuracy and reliability of external fetal monitoring techniques

OBJECTIVE

To evaluate the performance of external electronic fetal heart rate and uterine contraction monitoring according to maternal body mass index.

DESIGN

Secondary analysis of prospective equivalence study.

SETTING

Three US urban teaching hospitals.

SAMPLE

Seventy-four parturients with a normal term pregnancy.

METHODS

The parent study assessed performance of two methods of external fetal heart rate monitoring (abdominal fetal electrocardiogram and Doppler ultrasound) and of uterine contraction monitoring (electrohystero-graphy and tocodynamometry) compared with internal monitoring with fetal scalp electrode and intrauterine pressure transducer. Reliability of external techniques was assessed by the success rate and positive percent agreement with internal methods. Bland-Altman analysis determined accuracy. We analyzed data from that study according to maternal body mass index.

MAIN OUTCOME MEASURES

We assessed the relationship between body mass index and monitor performance with linear regression, using body mass index as the independent variable and measures of reliability and accuracy as dependent variables.

RESULTS

There was no significant association between maternal body mass index and any measure of reliability or accuracy for abdominal fetal electrocardiogram. By contrast, the overall positive percent agreement for Doppler ultrasound declined (p = 0.042), and the root mean square error from the Bland-Altman analysis increased in the first stage (p = 0.029) with increasing body mass index. Uterine contraction recordings from electrohysterography and tocodynamometry showed no significant deterioration related to maternal body mass index.

CONCLUSIONS

Accuracy and reliability of fetal heart rate monitoring using abdominal fetal electrocardiogram was unaffected by maternal obesity, whereas performance of ultrasound degraded directly with maternal size. Both electrohysterography and tocodynamometry were unperturbed by obesity.

Fetal electrocardiographic measurements in the assessment of fetal heart rate variability in the antepartum period

This study examines signal availability in fetal electrocardiogram (FECG) beat-to-beat acquisition and the accuracy of fetal heart rate variability (HRV) analysis in the clinical setting using a commercially available FECG monitor. Signal availability was examined in 130 FECG recordings of 0.3-17.5 h duration collected in 63 fetuses (25th-42nd week of gestation) under uncontrolled conditions. Identification of R-peaks demonstrated a signal loss of 30% ± 24% with 3.6 ± 1.7 signal gaps per minute. Median duration of the gaps within a recording was 1.8 ± 0.2 s. Per hour of recording, 1.8 ± 2.1 episodes of 5 min of uninterrupted data were found. Signal availability improved with gestational age and was poorer in women with high body-mass index. Fetal HRV between weeks 36-42 was examined on the basis of 5 min RR-interval episodes obtained under controlled quiet conditions in 55 FECG compared to 46 high quality fetal magnetocardiograms. There were no differences in RR-interval duration, its standard deviation and low frequency power. However, various measures of short-term HRV were significantly higher in the FECG data: root mean square of successive differences (10.0 ± 1.8 versus 6.6 ± 3.0 ms, p < 0.001, high frequency spectral power (24 ± 12 versus 13 ± 13 ms(2), p < 0.001) and approximate entropy (0.86 ± 0.16 versus 0.73 ± 0.24, p = 0.007). We conclude that, in spite of considerable signal loss, FECG recordings can accurately estimate heart rate and its overall variance. However, measures that quantify short-term beat-to-beat HRV will be compromised due to possible recurring inappropriate detection of single R-peaks.

Signal quality of non-invasive fetal electrocardiogram in vaginal breech delivery: a case-controlled study

OBJECTIVE

Recently, a non-invasive fetal electrocardiogram monitor has been approved for clinical usage in labour and delivery. To determine the fetal signal quality of vaginal breech deliveries in comparison with a case-controlled cephalic group during labour.

STUDY DESIGN

This case-control study was carried out at the Department of Obstetrics and Gynecology of the University Hospital Frankfurt between 1st July 2012 and 30th September 2012. A total of seven breech deliveries were evaluated. A case-controlled cephalic group with same gestational age and parity were selected from a previous trial.

RESULTS

During first stage of labour, vaginal breech and cephalic delivery had no significant different fetal signal success rates (mean 87.8 vs. 85.7 %; p > 0.05). There was a trend of higher fetal signal success rates in the vaginal breech delivery group during second stage of labour (78.4 vs. 55.4 %; p = 0.08).

CONCLUSION

Similar fetal signal success rates in vaginal breech delivery in comparison to cephalic presentation were demonstrated using the new commercially available non-invasive abdominal fECG device (the Monica AN24(TM)).

Intrapartum heart rate ambiguity: a comparison of cardiotocogram and abdominal fetal electrocardiogram with maternal electrocardiogram

OBJECTIVE/AIMS

To investigate the presence of signal ambiguity of intrapartum fetal heart rate (FHR) monitoring during delivery by comparing simultaneous cardiotocogram (CTG), abdominal fetal electrocardiogram (ECG) with continuous maternal ECG.

METHODS

A total of 144 simultaneous CTG (Corometrics 250 series), abdominal fetal ECG (Monica -AN24™) and maternal ECG (Monica AN24™) recordings were evaluated.

MAIN OUTCOME MEASURES

When the FHR is within 5 bpm of the maternal heart rate (MHR) acquired from the ECG, it is classified as 'MHR/FHR ambiguity'. Statistical analyses were performed with Fisher's exact test and the Wilcoxon signed-rank test.

RESULTS

Comparison of abdominal fetal ECG against CTG demonstrates significantly less 'MHR/FHR ambiguity' in both the first stage (mean 0.70 vs. 1.22%, p < 0.001) and second stage of labour (mean 3.30 vs. 6.20%, p < 0.001).

CONCLUSION

Intrapartum FHR monitoring in daily practice via the CTG modality provides significantly more 'MHR/FHR ambiguity' than abdominal fetal ECG, which also provides additional information on the MHR.

Misidentification of maternal for fetal heart rate patterns after delivery of the first twin

BACKGROUND

The 2nd born in twin delivery is at higher risk of fetal asphyxia. We tested the hypothesis that inadequate, fetal heart rate (FHR) monitoring has contributed to an inadvertent outcome.

STUDY DESIGN

A database was reviewed consisting of 41 twin deliveries with a pH in the umbilical artery of the 2nd twin below 7.05. Cardiotocograms were examined for possible signs of a maternal instead of a fetal origin of the heart rate pattern.

RESULTS

In four of the reviewed cases, a good outcome had been anticipated by the attending physician based on the cardiotocogram, whereas the 2nd twin was born with low Apgar scores and a low pH of the umbilical artery. In retrospect it was concluded that the recorded heart rate pattern was of maternal origin. In all four cases the heart rate tracings had characteristics typical for a maternal origin.

CONCLUSION

Misidentifying the maternal for the fetal heart rate increases the risk that a compromised fetal condition is missed. This occurrence may contribute to the increased incidence of fetal asphyxia in 2nd twins.

Fetal cardiac function assessed with four-dimensional ultrasound imaging using spatiotemporal image correlation

OBJECTIVES

The goal of this study was to use spatiotemporal image correlation (STIC) to provide reference values for left and right ventricle volumes, and indices of fetal cardiac function.

METHODS

In this prospective longitudinal study, STIC volumes were acquired periodically from 12 weeks of gestation onwards. The STIC volumes were frozen in end-systole and end-diastole, and volumetric data were measured by manual tracing and summation of multiple slices. These ventricle volumes were used to calculate stroke volume, ejection fraction and cardiac output.

RESULTS

Some 202 STIC volumes of 63 fetuses were included in the analysis. Mean left and right ventricle stroke volume increased from 0.02 mL at 12 weeks to 1.41 mL and 1.46 mL, respectively, at 30 weeks, while the mean right to left stroke volume ratio remained stable at around 1.2. Mean left and right ventricle cardiac output increased from 2.40 mL/min and 2.60 mL/min at 12 weeks to 197.74 mL/min and 204.81 mL/min, respectively, at 30 weeks. Both left and right mean ejection fraction remained constant at around 0.45 with advancing gestational age. Bland-Altman analysis showed a coefficient of variation for measured stroke volume of 13.7%.

CONCLUSIONS

This study establishes reference values for fetal cardiac volumes and indices for fetal cardiac function from 12 to 30 weeks of gestation using STIC. STIC seems to overcome many of the pitfalls of conventional ultrasound methods and has the potential to become the method of choice.

[Length of pushing efforts: pushing is not playing. Reply to the article of C. Le Ray and F. Audibert]

The aim of this work is to answer constructively to C. Le Ray and F. Audibert who were surprised that the French guidelines recommended an assisted delivery after 30 min pushing, even if the fetal heart rate is reassuring. We first resumed the definition of "second stage of labor", this word including the first phase with no pushing efforts and the second phase with active pushing of the mother. With that definition, the length of the second stage is around 60 min for the primipara and 20 min for the multipara, this length being modified by the use of peridural. We then specified the physiological mechanisms influencing the acidobasic equilibrium during the pushing time. Those mechanisms are difficult to consider because foetal heart rate monitoring is often "lost" during that phase. Altogether, these factors bring incertitude about progressive foetal acidosis and incapacity to diagnose it. Finally, the literature analysis teaches us that increasing the second stage of labor (inactive plus active phases) during the normal pregnancy seems to be at low risk for the foetus within the primiparas, but display a risk for the mother and so might be limited. Comparing the delayed pushing with the immediate pushing only lead us to conclude that delayed pushing is dangerous, as is prolonged second stage. In conclusion, we think that prolonging the second stage of labor is possible but must be by increasing the inactive first phase of the second stage, especially as long as we will not get a noninvasive and reliable method allowing assessing the well-being of the foetus.

Impact of fetal blood sampling on vaginal delivery and neonatal outcome in deliveries complicated by pathologic fetal heart rate: a population based cohort study

OBJECTIVE

To compare the impact of electronic fetal monitoring (EFM) alone vs. EFM with additional fetal blood sampling (FBS) in vaginal deliveries complicated by pathologic fetal heart rate (FHR).

METHODS

All deliveries in Hesse between 1990 and 2000 were evaluated for participation in this study. Inclusion criteria comprised (1) pathologic fetal heart rate, (2) singleton pregnancy, (3) cephalic presentation, (4) vaginal delivery, and (5) gestational age at delivery of more than 35 weeks' gestation. In order to analyze the meaning of additional risk factors at birth for the effectiveness of FBS two subgroups were selected depending on the presence of additional risk factors at birth. To examine the impact of FBS in deliveries with pathologic FHR on the mode of delivery and on neonatal outcome, univariate regression analysis was performed and odds ratios (OR) and their corresponding 95% confidence intervals (95% CI) were calculated.

RESULTS

The study population comprised 49,560 deliveries, among deliveries complicated by pathologic FHR, 26% underwent FBS. Deliveries with pathologic FHR and controlled by FBS, with no additional antepartum risk factors, were associated with an increase in spontaneous births OR 1.41 (95% CI 1.27-1.58), and in the presence of additional risk factors OR 1.24 (1.19-1.30). Short-term neonatal outcome parameters were characterized by a lower frequency of severe fetal acidosis (umbilical artery pH <7.0) OR 0.55 (0.42-0.72), and Apgar score <5 after 5 min, OR 0.71 (0.55-0.90).

CONCLUSION

In vaginal deliveries with pathologic FHR the use of FBS as an additional means of intrapartum fetal surveillance is associated with less vaginal operative deliveries, and with an improved short-term neonatal outcome.

Internal versus external intrapartum foetal heart rate monitoring: the effect on linear and nonlinear parameters

The effect of foetal heart rate (FHR) acquisition mode on linear and nonlinear parameters is still largely unknown. In 33 normal labouring women, FHR signals were acquired simultaneously by an external ultrasound sensor applied to the maternal abdomen and an internal scalp electrode, in the minutes preceding delivery. For each case, the initial and final 5, 10 and 20 min segments were analysed, considering FHR signals at a frequency of 4 Hz (the frequency at which they are transmitted by the majority of commercialized foetal monitors). Several time and frequency domain linear and nonlinear FHR indices were computed in these segments, namely mean FHR, very low frequency (VLF), low frequency (LF), high frequency (HF), approximate entropy (ApEn) and sample entropy (SampEn). Parametric confidence intervals, statistical tests and correlation coefficients were calculated in order to evaluate the effect of internal versus external FHR monitoring modes on the considered indices. The whole evaluation was repeated using FHR signals at a frequency of 2 Hz. Most time domain linear indices were similar with external and internal monitoring in the initial and final segments of the tracings. However, linear frequency domain indices were poorly correlated in the final segments and had significantly different mean values in the initial segments. Nonlinear indices were significantly different in both initial and final segments. The correlation between 4 and 2 Hz sampled parameters was high for both linear and nonlinear indices (most correlation coefficient values ranging between 0.95 and 1) but nonlinear index values were significantly higher at 2 Hz. In conclusion, the mode used to acquire FHR signals and the sampling rate employed can significantly affect most FHR indices.

Quality of intrapartum cardiotocography in twin deliveries

OBJECTIVE

Intrapartum fetal heart rate (FHR) recordings in twins were compared for fetal signal loss during both stages of labor to assess the quality of these recordings by the method that had been used: external ultrasound or directly via a scalp electrode.

STUDY DESIGN

Analysis of recordings collected between January 1, 1994, and January 1, 2002, from consecutive twin deliveries at the Vrije Universiteit Medical Center in Amsterdam. One hundred seventy-two twins that delivered via the vaginal route were included in the study. FHR recordings had a duration of at least 1 hour before the birth of the second twin. Subdivision took place on the basis of the recording technique, ie, ultrasound or scalp electrode. FHR data was obtained with HP-M1350 cardiotocographs. The status (pen on, pen off, maternal signal) and the mode of the signals were acquired. The duration of pen lifts and maternal signals was divided by the total duration of the recording. Statistical analyses were performed with the Mann-Whitney U test and the Wilcoxon signed ranks test.

RESULTS

Recordings obtained via ultrasound demonstrated significantly more fetal signal loss than those obtained via the direct mode, particularly in the second stage. Approximately 26% to 33% of first stage and 41% to 63% of second stage ultrasound intrapartum FHR recordings in twins exceeded the International Federation of Gynecology and Obstetrics (FIGO) criteria for fetal signal loss.

CONCLUSION

Intrapartum FHR monitoring via ultrasound provides far poorer quality FHR signals than the direct mode. The direct mode deserves a more prominent position in fetal surveillance than it currently has.