Literatura académica sobre el tema "ECG foetal"

We deal with the extraction of the fetal electrocardiography (ECG) signal from the raw ECG signals of the mother by the beamforming- based algorithms. The foetal ECG sensors bring out signals containing information from the pregnant mother and the infant. Detailed and separate signals are already provided by the foetal ECG instruments; but for some specific studies related to the infant conditions, it is necessary to improve the quality of the signal with a dedicated processing. In this paper, four techniques, with some enhancements, are proposed to perform the processing; we have applied the following techniques: Least Mean Square (LMS) with adaptive noise cancellation technique, Discrete Wavelet Transform (DWT)-based technique, Empirical Wavelet Transform (EWT) technique, and Multiple Signal Classification (MUSIC). The LMS and the MUSIC pertain to beamforming approach. The techniques were used to decompose and identify the different elements constituting the source signal (mother's signal) and noise cancellation by Multivariate Empirical Mode Decomposition (MEMD) technique. The signal was adaptively decomposed by LMS, DWT and MUSIC according to optimised parameters to extract some hidden components of the source signal, such as the foetal features, QRS, heartbeat etc. The results have showed that LMS, with enhancements, is more effective in identifying and removing useless noise. The techniques were applied to the ECG signal of a 30-year-old healthy pregnant woman, which allowed to verify their applicability. The present research leads to the below main contributions among others: separation of the ECG signal of the foetus from the mother, highlighting the functional state of the foetal heart rhythm (heart rate and heartbeat,) and this can show us if the foetal ECG has malfunctions.

The electrical activity of the foetal cardiac muscles is known as foetal ECG (FECG), and it can provide crucial details on the health of the fetus's heart. A pregnant woman's belly can be used to non-invasively capture this signal during pregnancy. However, since additional sources of noise, including the maternal ECG generally overpower the FECG recording, it would be ineffective. However, a clean FECG may be retrieved from the abdominal recording if it is correctly processed, and FECG can be used to evaluate the functioning of the foetal heart. In order to extract foetal electrocardiogram (ECG) from a single abdomen record, a unique two-tier approach is presented in this work. The abdominal signal is processed through a smoothing filter in the first layer of the proposed approach in order to determine the maternal ECG's estimated value. Findings on synthetic and actual abdominal ECG data demonstrate that the intended technique can extract foetal ECG with signal quality equivalent or superior to that retrieved by multichannel based mechanisms. The anticipated maternal ECG is then nonlinearly matched with the abdominal signal through polynomial networks.

L'analyse du rythme cardiaque fœtal (RCF) reste la technique la plus courante pour suivre le bien-être du fœtus et détecter la détresse fœtale pendant le travail et l'accouchement. Si la cardiotocographie (CTG) est aujourd'hui la technique clinique non invasive de référence pour la mesure du RCF, elle souffre de plusieurs inconvénients, ce qui pousse à s'intéresser à des technologies alternatives, comme l'électrocardiographie (ECG) et la phonocardiographie (PCG) abdominales.Une solution originale, utilisant un unique signal abdominal (ECG ou PCG), a été proposée pour répondre à la fois à la faisabilité en routine clinique et au défi de la difficile détection d'événements temporels dans des signaux enregistrés en conditions réelles. Basée sur l'algorithme de factorisation de matrices non négatives (NMF), elle exploite la semi-périodicité de l'ECG ou du PCG fœtal pour l'estimation du RCF.Le travail mené dans le cadre de cette thèse est d'une part expérimental et d'autre part algorithmique. Sur le plan expérimental, une base de données de 40 enregistrements sur femmes enceintes volontaires dans le dernier mois de grossesse a été constituée avec l'enregistrement synchrone de signaux ECG et PCG thoraciques et abdominaux, simultanément avec la CTG de référence. Elle a été analysée sur les plans expérimental et clinique. Du point de vue algorithmique, la méthode proposée, dans sa première version, supposait l'indépendance temporelle et ne tenait pas compte de la propriété de continuité des valeurs du RCF. Aussi, le travail algorithmique mené dans cette thèse a contribué à l'ajout dans le cadre NMF d'un modèle de Markov caché (HMM) pour inclure des informations physiologiques sur l'évolution temporelle du RCF. Cette proposition a été implémentée numériquement et évaluée sur la base de données réelles
Fetal heart rate (FHR) analysis remains the most common technique for monitoring fetal well-being and detecting fetal distress during labor and delivery. Although cardiotocography (CTG) is today the reference non-invasive clinical technique for measuring FHR, it suffers from a number of drawbacks, prompting interest in alternative technologies such as abdominal electrocardiography (ECG) and phonocardiography (PCG).An original solution, using a single abdominal signal (ECG or PCG), has been proposed to address both the feasibility in clinical routine and the challenge of the difficult detection of temporal events in signals recorded in real-life conditions. Based on the non-negative matrix factorization (NMF) algorithm, it exploits the semi-periodicity of the fetal ECG or PCG to estimate the FHR.The work carried out in this thesis is both experimental and algorithmic. On the experimental side, a database of 40 recordings from volunteer pregnant women in the last month of pregnancy was set up, with synchronous recording of thoracic and abdominal ECG and PCG signals, simultaneously with the reference CTG. It was analyzed both experimentally and clinically. From an algorithmic point of view, the first version of the proposed method assumed temporal independence, and did not take into account the property of continuity of FHR values. Therefore, the algorithmic work carried out in this thesis contributed to the addition of a Hidden Markov Model (HMM) to the NMF framework to include physiological information on the temporal evolution of the FHR. This proposal has been implemented numerically and evaluated on real data

Les malformations cardiaques congénitales sont la première cause de décès liés à une anomalie congénitale. L''electrocardiogramme du fœtus (ECGf), qui est censé contenir beaucoup plus d'informations par rapport aux méthodes échographiques conventionnelles, peut ˆêtre mesuré'e par des électrodes sur l'abdomen de la mère. Cependant, il est tr'es faible et mélangé avec plusieurs sources de bruit et interférence y compris l'ECG de la mère (ECGm) dont le niveau est très fort. Dans les études précédentes, plusieurs méthodes ont été proposées pour l'extraction de l'ECGf à partir des signaux enregistrés par des électrodes placées à la surface du corps de la mère. Cependant, ces méthodes nécessitent un nombre de capteurs important, et s'avèrent inefficaces avec un ou deux capteurs. Dans cette étude trois approches innovantes reposant sur une paramétrisation algébrique, statistique ou par variables d'état sont proposées. Ces trois méthodes mettent en œuvre des modélisations différentes de la quasi-périodicité du signal cardiaque. Dans la première approche, le signal cardiaque et sa variabilité sont modélisés par un filtre de Kalman. Dans la seconde approche, le signal est découpé en fenêtres selon les battements, et l'empilage constitue un tenseur dont on cherchera la décomposition. Dans la troisième approche, le signal n'est pas modélisé directement, mais il est considéré comme un processus Gaussien, caractérisé par ses statistiques à l'ordre deux. Dans les différentes modèles, contrairement aux études précédentes, l'ECGm et le (ou les) ECGf sont modélisés explicitement. Les performances des méthodes proposées, qui utilisent un nombre minimum de capteurs, sont évaluées sur des données synthétiques et des enregistrements réels, y compris les signaux cardiaques des fœtus jumeaux.

Estimation of the fetal heart rate (FHR) has gained interest in the last century; low heart rate variability has been studied to identify intrauterine growth restricted fetuses (prepartum), and abnormal FHR patterns have been associated with fetal distress during delivery (intrapartum). Several monitoring techniques have been proposed for FHR estimation, including auscultation and Doppler ultrasound. This thesis focuses on the extraction of the non-invasive fetal electrocardiogram (NI-FECG) recorded from a limited set of abdominal sensors. The main challenge with NI-FECG extraction techniques is the low signal-to-noise ratio of the FECG signal on the abdominal mixture signal which consists of a dominant maternal ECG component, FECG and noise. However the NI-FECG offers many advantages over the alternative fetal monitoring techniques, the most important one being the opportunity to enable morphological analysis of the FECG which is vital for determining whether an observed FHR event is normal or pathological. In order to advance the field of NI-FECG signal processing, the development of standardised public databases and benchmarking of a number of published and novel algorithms was necessary. Databases were created depending on the application: FHR estimation with or without maternal chest lead reference or directed toward FECG morphology analysis. Moreover, a FECG simulator was developed in order to account for pathological cases or rare events which are often under-represented (or completely missing) in the existing databases. This simulator also serves as a tool for studying NI-FECG signal processing algorithms aimed at morphological analysis (which require underlying ground truth annotations). An accurate technique for the automatic estimation of the signal quality level was also developed, optimised and thoroughly tested on pathological cases. Such a technique is mandatory for any clinical applications of FECG analysis as an external confidence index of both the input signals and the analysis outputs. Finally, a Bayesian filtering approach was implemented in order to address the NI-FECG morphology analysis problem. It was shown, for the first time, that the NI-FECG can allow accurate estimation of the fetal QT interval, which opens the way for new clinical studies on the development of the fetus during the pregnancy.

La surveillance de la santé foetale permet aux cliniciens d’évaluer le bien-être du foetus,de faire une détection précoce des anomalies cardiaques foetales et de fournir les traitementsappropriés. Les développements technologies actuels visent à permettre la mesurede l’électrocardiogramme (ECG) foetal de façon non-invasive afin d’extraire non seulementle rythme cardiaque mais également la forme d’onde du signal. Cet objectif est rendudifficile par le faible rapport signal sur bruit des signaux mesurés sur l’abdomen maternel.Cette mesure est donc toujours un challenge auquel se confrontent beaucoup d’études quiproposent des solutions de traitement de signal basées sur la seule modalité ECG.Le but de cette thèse est d’utiliser la modélisation des processus Gaussiens pour améliorerl’extraction des signaux cardiaques foetaux, dans une base multi-modale. L’ECG est utiliséconjointement avec le signal Phonocardiogramme (PCG) qui peut apporter une informationcomplémentaire à l’ECG. Une méthode générale pour la modélisation des signauxquasi-périodiques est présentée avec l’application au débruitage de l’ECG et à l’extractionde l’ECG du foetus. Différents aspects de la multi-modalité (synchronisation, · · · ) proposéesont étudiées afin de détecter avec plus de robustesse les battements cardiaques foetaux.La méthode considère l’application sur les signaux ECG et PCG à travers deux aspects:l’aspect du traitement du signal et l’expérimental. La modélisation des processus Gaussien,avec le signal PCG pris comme la référence, est utilisée pour extraire des modèles flexibleset des estimations non linéaires de l’information. La méthode cherche également à faciliterla mise en oeuvre pratique en utilisant un codage 1-bit des signaux de référence.Le modèle proposé est validé sur des signaux synthétiques et également sur des donnéespréliminaires réelles qui ont été enregistrées afin d’amorcer la constitution d’une base dedonnées multi-modale synchronisée. Les premiers résultats montrent que la méthode permettraà terme aux cliniciens d’étudier les battements cardiaques ainsi que la morphologiede l’ECG. Ce dernier aspect était jusqu’à présent limité à l’analyse d’enregistrements ECGinvasifs prélevés pendant l’accouchement par le biais d’électrodes posées sur le scalp dufoetus
Fetal health must be carefully monitored during pregnancy to detect early fetal cardiac diseases, and provide appropriate treatment. Technological development allows a monitoring during pregnancy using the non-invasive fetal electrocardiogram (ECG). Noninvasive fetal ECG is a method not only to detect fetal heart rate, but also to analyze the morphology of fetal ECG, which is now limited to analysis of the invasive ECG during delivery. However, the noninvasive fetal ECG recorded from the mother's abdomen is contaminated with several noise sources among which the maternal ECG is the most prominent.In the present study, the problem of noninvasive fetal ECG extraction is tackled using multi-modality. Beside ECG signal, this approach benefits from the Phonocardiogram (PCG) signal as another signal modality, which can provide complementary information about the fetal ECG.A general method for quasi-periodic signal analysis and modeling is first described and its application to ECG denoising and fetal ECG extraction is explained. Considering the difficulties caused by the synchronization of the two modalities, the event detection in the quasi-periodic signals is also studied which can be specified to the detection of the R-peaks in the ECG signal.The method considers both clinical and signal processing aspects of the application on ECG and PCG signals. These signals are introduced and their characteristics are explained. Then, using PCG signal as the reference, the Gaussian process modeling is employed to provide the possibility of flexible models as nonlinear estimations. The method also tries to facilitate the practical implementation of the device by using the less possible number of channels and also by using only 1-bit reference signal.The method is tested on synthetic data and also on real data that is recorded to provide a synchronous multi-modal data set.Since a standard agreement for the acquisition of these modalities is not yet taken into much consideration, the factors which influence the signals in recording procedure are introduced and their difficulties and effects are investigated.The results show that the multi-modal approach is efficient in the detection of R-peaks and so in the extraction of fetal heart rate, and it also provides the results about the morphology of fetal ECG

Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2015
O Developing Human Connectome Project pretende realizar um progresso científico único através da criação do primeiro connectome 4D no início da vida do bebé. De forma a criar um mapa dinâmico da conectividade do cérebro do bebé, é fundamental obter imagens funcionais e com ponderação em difusão. A imagem eco-planar (EPI) é a principal sequência de ressonância magnética aplicada na aquisição dessa informação. Esta sequência permite uma aquisição rápida e repetida de imagens cerebrais permitindo mapear as flutuações da atividade cerebral (imagiologia funcional) bem como ter uma boa resolução nas imagens de difusão (movimento de moléculas de água no volume cerebral). No entanto, esta técnica está associada a artefactos de suscetibilidade. Estes artefactos surgem quando existem interfaces entre duas amostras com suscetibilidades magnéticas diferentes como sejam o tecido biológico e o ar. De forma a minimizar esses artefactos é necessário reduzir as heterogeneidades do campo magnético principal B0 através de shimming. O presente trabalho focou-se em shimming ativo, no qual o campo magnético é mapeado com base num modelo composto por funções harmónicas esféricas e são calculadas as correntes a aplicar às bobinas de shimming. Essas bobinas geram um campo magnético que compensa as heterogeneidades presentes anteriormente. Convencionalmente, as tentativas para superar este problema envolvem a utilização do método disponibilizado no sistema de ressonância magnética, nas quais o campo é mapeado com base em projecções (ex: FASTMAP). Este método é de execução rápida mas apresenta duas desvantagens principais: em primeiro lugar, o utilizador tem um controlo reduzido sobre o processo; em segundo, as regiões nas quais o campo é mapeado não são definidas com base na anatomia de interesse. No contexto deste trabalho, o controlo sobre o processo é importante no sentido de ser possível aplicar exatamente a mesma metodologia a um grupo elevado de sujeitos. Por seu lado, o mapeamento com base na anatomia permite obter uma optimização mais precisa. Com o surgimento de novas tecnologias passou a ser possível fazer um mapeamento mais detalhado do campo magnético com técnicas baseadas em imagem ao invés de projecções. Estas técnicas envolvem a definição de um volume relacionado com a anatomia, e que é incluído na totalidade na optimização do campo. O principal objetivo deste trabalho foi desenvolver uma ferramenta de shimming baseado em imagem a fim de otimizar o campo magnético no contexto de imagens de EPI do cérebro neonatal e fetal. O cérebro do bebé sofre alterações na sua dimensão e forma durante o seu desenvolvimento desde a idade fetal até neonatal. Em cada uma dessas fases o bebé encontra-se cercado por um ambiente diferente que requere uma abordagem específica ao mesmo. Neste sentido, o trabalho desenvolvido foi dividido em três partes principais: descrição da estrutura necessária para a correta aplicação do shimming, shimming neonatal e shimming fetal. Em primeiro lugar, as limitações do shimming baseado em imagem foram estudadas e o algoritmo básico para aplicar o método foi testado. Nesta parte do trabalho foi demonstrado que os campos gerados pelas bobinas de shim presentes no equipamento de ressonância magnética são consistentes com as funções harmónicas esféricas que compõem o modelo aplicado. O efeito do movimento da cama do equipamento sobre a eficiência do shimming foi também estudada. Foi possível corrigir a informação do sistema de coordenadas que descrevem o mapa de campo B0 de forma a incluir o movimento da cama necessário para a obtenção das imagens em sujeitos fetais. A segunda parte do trabalho focou-se no desenvolvimento do shimming para o caso neonatal. Foi desenvolvida uma ferramenta para definição de uma região de interesse, unwrapping da fase e cálculo das correntes de shim. Esta foi desenvolvida em ambiente MATLAB. Nos recém-nascidos o shimming deve ser aplicado numa região de interesse restrita ao cérebro devido à presença da interface ar/tecido no escalpe do bebé. Assim, a definição da região de interesse consistiu principalmente na aplicação de um limiar a fim de binarizar a imagem de magnitude, ajustada pelo utilizador. Em simultâneo foi implementada uma técnica de exclusão dos olhos com base na anatomia dos diferentes planos. No seu conjunto o método apresentou-se flexível de forma a ser ajustado ao sujeito em estudo. Quando aplicado com a mesma metodologia (limiar e exclusão de olhos) o volume incluído foi semelhante entre bebés. O método de shimming foi avaliado com base em três medidas de dispersão do mapa de campo residual: largura a meia altura, desvio padrão dos pixéis no interior da região de interesse e o intervalo de frequências no interior do qual 95 % dos pixéis se encontravam. A utilização de diferentes medidas permitiu a avaliação do m´etodo em relação a diferentes aspetos. Este método foi aplicado a 52 participantes recém-nascidos com idade gestacional média de 39.8 ± 1.7 semanas. O cálculo das correntes de shim permitiu gerar um campo magnético que melhorou a homogeneidade do campo B0 no volume adquirido, sendo consistente com o previsto. Uma imagem média do campo residual foi calculada mostrando que existem duas regiões (occipital e pequenas regiões laterais) nas quais o campo magnético B0 apresenta ainda heterogeneidades. Por fim, os resultados indicam que este método melhorou o campo perto da periferia do cérebro quando comparado com o método convencional disponibilizado no equipamento. O shimming neonatal (shimming ótimo ou OIBS) foi utilizado como alicerce para a implementação de um método ajustado às características das aquisições fetais. Existem duas características principais que devem ser tidas em conta. Em primeiro lugar, os fetos encontram-se envoltos em líquido amniótico e tecido materno pelo que o ambiente no qual estão inseridos permite que a região de interesse seja definida de forma menos restrita. Em segundo lugar, o facto de a cabeça do feto ser pequena pode levar à existência de valores de corrente das bobinas de shim elevados. Essas correntes, principalmente associadas às bobinas de segunda ordem geram campos de magnitude elevada na região do tecido adiposo, o que altera a sua frequência de ressonância. Desta forma, as técnicas de supressão de gordura específicas em frequência são menos efetivas e a imagem de EPI apresenta artefactos. Assim, a ferramenta para shimming fetal incluiu a definição de uma região de interesse cilíndrica e um método de shimming baseado em imagem com limites lineares (shimming limitado ou CIBS) impostos com base na frequência de ressonância do tecido adiposo. O CIBS consistiu na aplicação de limites superiores e inferiores ([-300 100] Hz) para a frequência dos pixéis pertencentes à gordura após a aplicação do shimming. Adicionalmente, o impulso de radiofrequência utilizado para a supressão de gordura foi estudado a fim o otimizar para a sua utilização no contexto do shimming fetal. Para o estudo dos parâmetros do impulso de radiofrequência, os rins de dois voluntários adultos saudáveis foram utilizados como simulação do ambiente fetal, devido as semelhanças entre a localização e interface entre tecidos. Os métodos OIBS e CIBS foram aplicados em 6 grávidas saudáveis com idades gestacional média de 28±6 semanas. Os mapas de campo residuais mostraram que as técnicas eram semelhantes em termos de homogeneidade no interior da região de interesse definida como cérebro, mas a segunda (CIBS) apresentou melhores resultados na supressão de gordura. Como estudo do impulso de radiofrequência foi demonstrado que o desvio do impulso em cerca de 100 Hz no sentido da frequência de ressonância da água melhoraria a supressão de gordura sem detrimento do sinal da água. A utilização do novo método CIBS em simultâneo com um impulso de radiofrequência otimizado mostrou ser a melhor solução para homogeneizar o campo e suprimir a gordura. Em conclusão, as ferramentas apresentadas permitiram melhorar a qualidade das imagens de EPI da cabeça do feto e do recém-nascido no contexto do Developing Human Connectome Project. O shimming neonatal mostrou ser um método consistente que pode facilmente ser utilizado por parte da equipa clínica. A nível fetal foi apresentado um método que demonstra a capacidade de superar as limitações demonstradas pelas técnicas convencionais.
The Developing Human Connectome Project (dHCP) aims to make major scientific progress by creating the first 4-dimensional connectome of early life. Echo planar imaging (EPI) is the main acquisition technique applied in functional and diffusion imaging, which are central to map the human brain. This technique allows fast acquisition of spatial information enabling volumetric coverage of the whole brain, but it is associated with susceptibility artefacts. In order to minimize those artefacts it is necessary to reduce main magnetic field B0 in homogeneities through shimming. Conventionally, the attempts to overcome this problem use the manufacturer’s default method. Unfortunately, with those techniques the user has little control over the process, and the regions within which the field is corrected are not anatomically based. The main objective of this project was to develop an image-based shimming tool to optimize the magnetic field in the context of EPI images adjusted to the neonatal and foetal brains. The babies’ brain suffers changes in dimension and shape during its development from foetal to neonatal age. In each one of those stages the baby is surrounded by a different environment which requires a distinct shimming approach. As a result, the work was divided into three main parts: framework description, neonatal shimming and foetal shimming. First, the limitations of image-based shimming were investigated, and the framework to apply the method was described. It was demonstrated that fields generated by shim coils were consistent with the spherical harmonic model applied. In addition, the coordinate information of the B0 field map was corrected in order to include the table displacement needed for foetal imaging. Second, a tool was developed for neonatal shimming. The tool included region-of-interest (ROI) definition, phase unwrapping and shim calculation. The ROI definition implemented was flexible in order to adjust to each subject under study. When applying this approach while keeping the same threshold/eye exclusion methodology the volume included was similar between babies. The shim calculation allowed to generate shim values that improved homogeneity of the magnetic field within the volume imaged. This method slightly improved the field near the brain’s margins when compared with the manufacturer’s default techniques. Finally, for foetal shimming the groundwork of the neonatal tool was adjusted to this cohort characteristics. The tool for foetal shimming included additional cylindrical ROI definition and constrained image-based shimming. The constrained shimming allowed to account for the mother’s adipose tissue which in the presence of high shim values can lead to imperfect fat suppression. Along with the implementation of shimming tools, the radio frequency pulse used for fat suppression was studied. The new constrained image-based shimming showed similar results in terms of field homogeneity within the fetus’ brain when compared with the optimal image based shimming, with improvement of fat suppression that is enhanced when simultaneously used with the optimized fat suppression radiofrequency pulse.

Abstract Cells in culture are widely used as experimental models to study pro-oxidant and antioxidant responses. Although the conditions used are usually simple, and the results are obtained easily and rapidly, proteins, e.g. foetal calf serum, can act as radical scavengers, and iron and copper salts can also contaminate culture media during free-radical experiments. Appropriate controls must therefore be included and conditions carefully standardized, for example by using foetal calf serum (FCS)-free media.

A number of studies have shown that foetal nutritional status significantly impacts an unborn child’s long-term health. The developmental origins of health and disease (DOHaD) hypothesis proposes that if a child is undernourished in the foetal period, the child will develop diabetes and hypertension in the future if adequate nutrition is given after birth. Moreover, hyperglycaemia (e.g. gestational diabetes mellitus [GDM]) experienced during foetal life can reportedly cause various complications in children. As diabetes is increasing worldwide, so is GDM, and many studies have been conducted using GDM animal models and GDM cell lines. We examined the effects of streptozotocin-induced diabetes, particularly on the heart of offspring, in rat GDM animal models. We also analysed primary cardiomyocyte cultures isolated from these GDM rats and found that insulin signalling was inhibited in GDM cells, as in the GDM animal models, by increased advanced glycation end products. Furthermore, the effect of eicosapentaenoic acid during pregnancy has been reported in GDM animal models and cells, and the findings indicated the importance of nutritional management for GDM during pregnancy.

Caesarean section on maternal request (CSMR) is performed in the absence of a standard medical/obstetrical indication in order to avoid vaginal delivery. Globally, there has been an upsurge in CS delivery, which necessitates the urgency to address maternal and foetal health implications, and long-term repercussions. Conceptually, the chapter aims to explore the determinants of increased CSMR, highlight its potential risks and benefits, and discuss the ethical, medico-legal concerns. Findings indicate that medical, psychological, psychosocial, economical, social and cultural determinants might serve as some of the potential influencing factors owing to this serious healthcare concern. Although CSMR has been linked to certain beneficial outcomes (e.g. reduced urinary incontinence and pelvic organ prolapse, reduced rate of PTSD and depression, and lesser intrapartum complications), it still imposes serious maternal (e.g. post-partum haemorrhage and infection, visceral damage, placenta accrete, placental abruption and complications in future pregnancy) and foetal adverse outcomes (stillbirth, asphyxia, respiratory distress and other pulmonary infections). Hence, future approaches and interventions should be directed towards mitigating clinically unrequired CS procedures due to medical malpractices, lack of awareness in women and the underlying determinants of elective CS.

Abstract At least 95 per cent of the menstrual cycles of healthy, reproductive-aged women are ovulatory (Vollman, 1977). However, for the average non-contracepting couple, there is only about a 25 per cent chance that an ovum will produce a recognized pregnancy (Leridon, 1977). This gap between the number of available ova and the much smaller number of observed pregnancies presumably reflects some mixture of failure to conceive and early death of the conceptus. The rate of fertilization in humans is unknown, because we have no method to detect the event of fertilization. That, in turn, makes us unable to measure the proportion of fertilized ova lost before pregnancy becomes clinically apparent. In principle, the risk of early loss could range from zero (assuming that 25 per cent of ova are fertilized and all survive) to nearly 75 per cent (assuming that every egg is fertilized but only 25 per cent survive).