64 research outputs found

    Reducing stillbirths: screening and monitoring during pregnancy and labour

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    <p>Abstract</p> <p>Background</p> <p>Screening and monitoring in pregnancy are strategies used by healthcare providers to identify high-risk pregnancies so that they can provide more targeted and appropriate treatment and follow-up care, and to monitor fetal well-being in both low- and high-risk pregnancies. The use of many of these techniques is controversial and their ability to detect fetal compromise often unknown. Theoretically, appropriate management of maternal and fetal risk factors and complications that are detected in pregnancy and labour could prevent a large proportion of the world's 3.2 million estimated annual stillbirths, as well as minimise maternal and neonatal morbidity and mortality.</p> <p>Methods</p> <p>The fourth in a series of papers assessing the evidence base for prevention of stillbirths, this paper reviews available published evidence for the impact of 14 screening and monitoring interventions in pregnancy on stillbirth, including identification and management of high-risk pregnancies, advanced monitoring techniques, and monitoring of labour. Using broad and specific strategies to search PubMed and the Cochrane Library, we identified 221 relevant reviews and studies testing screening and monitoring interventions during the antenatal and intrapartum periods and reporting stillbirth or perinatal mortality as an outcome.</p> <p>Results</p> <p>We found a dearth of rigorous evidence of direct impact of any of these screening procedures and interventions on stillbirth incidence. Observational studies testing some interventions, including fetal movement monitoring and Doppler monitoring, showed some evidence of impact on stillbirths in selected high-risk populations, but require larger rigourous trials to confirm impact. Other interventions, such as amniotic fluid assessment for oligohydramnios, appear predictive of stillbirth risk, but studies are lacking which assess the impact on perinatal mortality of subsequent intervention based on test findings. Few rigorous studies of cardiotocography have reported stillbirth outcomes, but steep declines in stillbirth rates have been observed in high-income settings such as the U.S., where cardiotocography is used in conjunction with Caesarean section for fetal distress.</p> <p>Conclusion</p> <p>There are numerous research gaps and large, adequately controlled trials are still needed for most of the interventions we considered. The impact of monitoring interventions on stillbirth relies on use of effective and timely intervention should problems be detected. Numerous studies indicated that positive tests were associated with increased perinatal mortality, but while some tests had good sensitivity in detecting distress, false-positive rates were high for most tests, and questions remain about optimal timing, frequency, and implications of testing. Few studies included assessments of impact of subsequent intervention needed before recommending particular monitoring strategies as a means to decrease stillbirth incidence. In high-income countries such as the US, observational evidence suggests that widespread use of cardiotocography with Caesarean section for fetal distress has led to significant declines in stillbirth rates. Efforts to increase availability of Caesarean section in low-/middle-income countries should be coupled with intrapartum monitoring technologies where resources and provider skills permit.</p

    Fetal autonomic cardiac response during pregnancy and labour

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    Timely recognition of fetal distress, during pregnancy and labour, in order to intervene adequately is of major importance to avoid neonatal morbidity and mortality. As discussed in chapter 1, the cardiotocogram (CTG) might be a useful screening test for fetal monitoring but it has insufficient specificity and requires additional diagnostic tests in case of suspected fetal compromise to avoid unnecessary operative deliveries. Potential additional techniques used in clinical practice are fetal scalp blood sampling (FBS) and ST-waveform analysis of the fetal electrocardiogram (ECG; STAN®). However, publications on these techniques provide limited support for the use of these methods in the presence of a non-reassuring CTG for reducing caesarean sections. In addition, these techniques are invasive and can therefore only be used during labour at the term or the near term period. Consequently, it is of great clinical importance that additional methods are developed that contribute to more reliable assessment of fetal condition. Preferably, this information is obtained non-invasively. Valuable additional information on the fetal condition can possibly be obtained by spectral analysis of fetal heart rate variability (HRV). The fetal heart rate fluctuates under the control of the autonomic part of the central nervous system. The autonomic cardiac modulation is discussed in chapter 2. The sympathetic and parasympathetic nervous systems typically operate on partly different timescales. Time-frequency analysis (spectral analysis) of fetal beat-to-beat HRV can hence quantify sympathetic and parasympathetic modulation and characterise autonomic cardiac control . The low frequency (LF) component of HRV is associated with both sympathetic and parasympathetic modulation while the high frequency (HF) component is associated with parasympathetic modulation alone2. Spectral estimates of HRV might indirectly reflect fetal wellbeing and increase insight in the human fetal autonomic cardiac response. In chapter 3, technical details for retrieving fetal beat-to-beat heart rate and its spectral estimates are provided. In this thesis spectral analysis of fetal HRV is investigated. The first objective is to study the value of spectral analysis of fetal HRV as a tool to assess fetal wellbeing during labour at term. The second objective is to monitor spectral estimates of fetal HRV, non-invasively, during gestation to increase insight in the development of human fetal autonomic cardiac control. Since Akselrod reported the relation between autonomic nervous system modulation and LF and HF peaks in frequency domain1, frequency analysis of RR interval fluctuations is widely performed . For human adults, standards for HRV measurement and physiological interpretation have been developed2. Although HRV parameters are reported to be highly prognostic in human adults in case of cardiac disease, little research is done towards the value of these parameters in assessing fetal distress in the human fetus, as shown in chapter 4. In this chapter, the literature about time-frequency analysis of human fetal HRV is reviewed in order to determine the value of spectral estimates for fetal surveillance. Articles that described spectral analysis of human fetal HRV and compared the energy in spectral bands with fetal bloodgas values were included. Only six studies met our inclusion criteria. One study found an initial increase in LF power during the first stage of fetal compromise, which was thought to point to stress-induced sympathetic hyperactivity3. Five out of six studies showed a decrease in LF power in case of fetal distress , , , , ,. This decrease in LF power in case of severe fetal compromise was thought to be the result of immaturity or decompensation of the fetal autonomic nervous system. These findings support the hypothesis that spectral analysis of fetal HRV might be a promising method for fetal surveillance. All studies included in the literature review used absolute values of LF and HF power. Although absolute LF and HF power of HRV provide useful information on autonomic modulation, especially when considering fetal autonomic development, LF and HF power may also be measured in normalised units. Normalised LF (LFn) and normalised HF power (HFn) of HRV represent the relative value of each power component in proportion to the total power2. Adrenergic stimulation can cause a sympathetically-modulated increase in fetal heart rate . A negative correlation however exists between heart rate and HRV . As a result, the sympathetic stimulation can decrease the total power of HRV and even the absolute LF power. When normalising the absolute LF (and HF) with respect to the total power, a shift in activity from HFn to LFn might become visible, revealing the expected underlying sympathetic activity. Thus, because changes in total power influence absolute spectral estimates in the same direction, normalised values of LF and HF power seem more suitable for fetal monitoring. In other words, normalised spectral estimates detect relative changes that are no longer masked by changes in total power2. LFn and HFn power are calculated by dividing LF and HF power, respectively, by total power and represent the controlled and balanced behaviour of the two branches of the autonomic nervous system2. In chapter 5 we hypothesised that the autonomic cardiovascular control is functional in fetuses at term, and that LFn power increases in case of distress due to increased sympathetic modulation. During labour at term, ten acidaemic fetuses were compared with ten healthy fetuses. During the last 30 minutes of labour, acidaemic fetuses had significantly higher LFn power and lower HFn power than control fetuses, which points to increased sympathetic modulation. No differences in absolute LF or HF power were found between both groups. The observed differences in normalised spectral estimates of HRV were not observed earlier in labour. In conclusion, it seems that the autonomic nervous system of human fetuses at term responds adequately to severe stress during labour. Normalised spectral estimates of HRV might be able to discriminate between normal and abnormal fetal condition. Although we found significant differences in normalised spectral estimates between healthy and acidaemic fetuses, we wondered whether spectral power of HRV is also related to fetal distress in an earlier stage. The next step in chapter 6 was therefore, to investigate whether spectral estimates are related to fetal scalp blood pH during labour. Term fetuses during labour, in cephalic presentation, that underwent one or more scalp blood samples were studied. Beat-to-beat fetal heart rate segments, preceding the scalp blood measurement, were used to calculate spectral estimates. In total 39 FBS from 30 patients were studied. We found that normalised spectral estimates are related to fetal scalp blood pH while absolute spectral estimates are not related to fetal pH. It was further demonstrated that LFn power is negatively related and HFn power is positively related to fetal pH. These findings point to increased sympathetic and decreased parasympathetic cardiac modulation in human fetuses at term upon decrease of their pH value. This study confirms the hypothesis that normalised spectral values of fetal HRV are related to fetal distress in an early stage. Previous studies showed that absolute LF and HF power increase as pregnancy progresses, which is attributed to fetal autonomic maturation , . Since it is yet unclear how LFn and HFn evolve with progressing pregnancy, before using spectral analysis for fetal monitoring, it has to be determined whether gestational age has to be corrected for. In addition, fetal autonomic fluctuations, and thus spectral estimates of HRV, are influenced by fetal behavioural state . Since these states continue to change during labour , thorough understanding of the way in which these changes in state influence spectral power is necessary for the interpretation of spectral values during labour at term. Therefore, in chapter 7, we examined whether differences in spectral estimates exist between healthy near term and post term fetuses during labour. In case such differences do exist, they should be taken into consideration for fetal monitoring. The quiet and active sleep states were studied separately to determine the influence of fetal behavioural state on spectral estimates of HRV during labour around term. No significant differences in spectral estimates were found between near term and post term fetuses during active sleep. During quiet sleep, LFn power was lower and HF and HFn power were higher in post term compared to near term fetuses, no significant differences in LF power were observed between both groups. LF, HF and LFn power were higher and HFn power was lower during active sleep compared to quiet sleep in both groups. This seems to point to sympathetic predominance during the active state in fetuses around term. In addition, post term parasympathetic modulation during rest seems increased compared to near term. In conclusion, fetal behavioural state and gestational age cause a considerable variability in spectral estimates in fetuses during labour, around term, which should be taken into consideration when using spectral estimates for fetal monitoring. In chapters 4 to 6, spectral estimates of beat-to-beat fetal HRV were studied using fetal ECG recordings that were obtained directly from the fetal scalp during labour. However, the second objective of this thesis is to obtain spectral estimates non-invasively during gestation to increase insight in the development of human fetal autonomic cardiac control. The fetal ECG is also present on the maternal abdomen, although much smaller in amplitude and obscured by the maternal ECG and noise. Chapter 8 focused on non-invasive measurement of the fetal ECG from the maternal abdomen. These measurements allow for obtaining beat-to-beat fetal heart rate non-invasively. Therefore, this method can be used to obtain spectral estimates of fetal HRV throughout gestation. Although abdominal recording of the fetal ECG may offer valuable additional information, it is troubled by poor signal-to-noise ratios (SNR) during certain parts of pregnancy, e.g. during the immature period and during the vernix period. To increase the usability of abdominal fetal ECG recordings, an algorithm was developed that uses a priori knowledge on the physiology of the fetal heart to enhance the fetal ECG components in multi-lead abdominal fetal ECG recordings, before QRS-detection. Evaluation of the method on generated fetal ECG recordings with controlled SNR showed excellent results. The method for non-invasive fetal ECG and beat-to-beat heart rate detection presented in chapter 8 was used for analysis in chapter 9. The feasibility of this method in a longitudinal patient study was investigated. In addition, changes in spectral estimates of HRV during pregnancy were studied and related to fetal rest-activity state to study the development of fetal autonomic cardiac control. We found that approximately 3% of non-invasive fetal ECG recordings could be used for spectral analysis. Therefore, improvement of both equipment and algorithms is still needed to obtain more good-quality data. The percentage of successfully retrieved data depends on gestational age. Before 18 and between 30 and 34 weeks no good-quality beat-to-beat heart rate data were available. We found an increase in LF and HF power of fetal HRV with increasing gestational age, between 21 to 30 weeks of gestation. This increase in LF and HF power is probably due to increased sympathetic and parasympathetic modulation and might be a sign of autonomic development. Furthermore, we found sympathetic predominance during the active state compared to the quiet state in near term fetuses (34 to 41 weeks of gestation), comparable to the results observed during labour around term. During 34 to 41 weeks a (non-significant) decrease in LF and LFn power and a (non-significant) increase in HF and HFn power were observed. These non-significant changes in spectral estimates in near term fetuses might be associated with changes in fetal rest-activity state and increased parasympathetic modulation as pregnancy progresses. However, more research is needed to confirm this

    Non-invasive electrophysiologic measurements of the fetus during pregnancy and labor

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    Complex interventions in midwifery care: Reflections on the design and evaluation of an algorithm for the diagnosis of labour

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    Randomised controlled trials are the ‘gold standard’ for evaluating the effectiveness of interventions in health-care settings. However, in midwifery care, many interventions are ‘complex’, comprising a number of different elements which may have an effect on the impact of the intervention in health-care settings. In this paper we reflect on our experience of designing and evaluating a complex intervention (a decision tool to assist with the diagnosis of labour in midwifery care), examining some of the issues that our study raises for future research in complex interventions

    Adjunctive technologies for intrapartum fetal monitoring: current perspectives and proof of concept for a novel approach

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    Fetal monitoring is a recurring theme in perinatal morbidity and mortality reports, highlighting the limitations of cardiotocography and current adjunctive technologies, such as fetal blood sampling (FBS). There is an unmet need for more robust methods of intrapartum fetal assessment. Microdialysis may help to detect babies at risk of hypoxia by monitoring trends in lactate and related metabolites from fetal scalp interstitial fluid in a minimally invasive manner. However, its clinical value remains unproven because there is limited evidence on the relationship between interstitial and arterial lactate. Translating advances in fetal monitoring technology into improved clinical outcomes also depends on how obstetricians use such technology in their practice, which few past studies have explored in depth. This research comprised two components. The first part aimed (1) to develop a neonatal piglet model of hyperlactataemia; and, using this model, (2) to investigate the relationship between interstitial and arterial lactate; and (3) to explore the feasibility of using subcutaneous microdialysis to monitor the metabolic response to hypoxia in vivo. Eight neonatal piglets were monitored under non-recovery general anaesthesia. Hyperlactataemia was achieved by means of alveolar hypoxia and/or intravenous sodium L-lactate infusion, with target lactate concentrations above 12 mmol/L. Microdialysate from two subcutaneous microdialysis catheters inserted into the scalp of each piglet was analysed for interstitial lactate, pyruvate, glucose and glutamate concentrations, which were compared to arterial blood gas measurements. A subset of dialysate samples underwent secondary analyses with the StatStrip Xpress® pointof- care lactate meter to assess its performance. In total, 432 dialysate samples were collected from seven piglets. There was variation in the piglets’ response to hypoxia therefore two piglets received lactate infusions, with four overall achieving target hyperlactataemia. Interstitial lactate, pyruvate and glucose concentrations were not affected by microdialysis catheter insertion. There was a strong positive correlation between arterial lactate and interstitial lactate, and weaker positive correlations with interstitial lactate-to-pyruvate and lactate-to-glucose ratios. Interstitial lactate mirrored trends in arterial lactate with an approximate time lag of 10 v to 20 min, although the closeness of agreement varied between piglets. StatStrip Xpress® lactate values showed a proportional negative bias relative to the reference microdialysis analyser, but trend data and assay precision were comparable. The second part of this research sought to understand how UK obstetricians use adjunctive fetal monitoring technologies and what factors influence their practice, as well as exploring attitudes towards new technology and other areas for improving practice. Data were collected through semi-structured telephone interviews with 16 obstetricians of varying career grade from nine maternity units across the UK, prior to thematic analysis. Most obstetricians reported performing FBS but attitudes towards it varied. The use of fetal monitoring technology was influenced by obstetricians’ individual clinical autonomy, the socio-cultural norms of their unit, and wider external factors, such as guidelines. Obstetricians recognised the limitations of current methods of monitoring, but enthusiasm towards new technology was checked by a scepticism of ‘computerisation’ and perceived barriers to changing practice; hence, better staff training was seen as the immediate priority for improving outcomes. In summary, the work presented in this thesis provides new insight into the current role of adjunctive technologies in UK obstetric practice and demonstrates proof of concept for subcutaneous microdialysis as a novel approach to monitoring metabolic wellbeing in the fetus and neonate. Although interstitial lactate reflected trends in arterial lactate in response to hypoxia and lactate infusion in neonatal piglets, further research is required to fully characterise this relationship, including standardisation of the hyperlactataemia model described here. This research has also identified a range of individual and contextual factors that influence how obstetricians use fetal monitoring technology and highlights the urgent need for future qualitative studies to improve understanding of this complex process, alongside efforts to develop new technology

    A study of an intelligent system to support decision making in the management of labour using the cardiotocograph - the INFANT study protocol

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    Background Continuous electronic fetal heart rate monitoring in labour is widely used but its potential for improving fetal and neonatal outcomes has not been realised. The most likely reason is the difficulty of interpreting the fetal heart rate trace correctly during labour. Computerised interpretation of the fetal heart rate and intelligent decision-support has the potential to deliver this improvement in care. This trial will test whether the addition of decision support software to aid the interpretation of the cardiotocogram (CTG) during labour will reduce the number of ‘poor neonatal outcomes’ in those women judged to require continuous electronic fetal heart rate monitoring. Methods and design An individually randomised controlled trial of 46,000 women who are judged to require continuous electronic fetal monitoring in labour. Eligibility criteria: Women admitted to a participating labour ward who are judged to require continuous electronic fetal monitoring, have a singleton or twin pregnancy, are ≥ 35 weeks’ gestation, have no known gross fetal abnormality and are ≥ 16 years of age. Exclusion criteria: Triplets or higher order pregnancy, elective caesarean section prior to the onset of labour, planned admission to NICU. Trial interventions: Computerised interpretation of the CTG with decision-support. Primary outcomes: Short term: A composite of ‘poor neonatal outcome’ including stillbirth after trial entry, early neonatal death except deaths due to congenital anomalies, significant morbidity: neonatal encephalopathy, admissions to the neonatal unit with 48 h for > 48 h with evidence of feeding difficulties, respiratory illness or encephalopathy where there is evidence of compromise at birth. Long term: Developmental assessment at the age of 2 years in a subset of 7000 surviving babies. Data Collection: For all participating women and babies, labour variables and outcomes will be stored automatically and contemporaneously onto the Guardian® system. Discussion The results of this trial will have importance for pregnant women and for health professionals who provide care for them

    Automatická detekce pohybu plodu pomocí abdominální elektrokardiografie

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    The aim of the bachelor’s thesis is to introduce an extensive review of fetal movement monitoring methods. The theoretical part describes currently available fetal monitoring methods, primarily non-invasive fetal electrocardiography. The thesis continues to thoroughly describe and characterize fetal movements and the current possibilities of fetal movement detection. The output of the bachelor’s thesis is an analysis of the manifestation of fetal movements on various biological signals, which were further used in the design and development of the graphical user interface for automatic fetal movement detection. Developed fetal movement detection algorithms were evaluated on clinical practice data.Hlavním cílem předložené bakalářské práce je představit rozsáhlý přehled metod sledování pohybu plodu. V teoretické části jsou popsány momentálně dostupné metody monitorování plodu, především neinvazivní fetální elektrokardiografie. Předložená bakalářská práce dále důkladně popisuje a charakterizuje pohyby plodu a současné možnosti detekce pohybu plodu. Výstupem bakalářské práce je analýza projevů pohybů plodu na různých biologických signálech, které byly dále využity při návrhu a vývoji grafického uživatelského rozhraní pro automatickou detekci pohybu plodu. Vyvinuté algoritmy byly následně vyhodnoceny na datech z klinické praxe.450 - Katedra kybernetiky a biomedicínského inženýrstvívýborn
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