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- Development and evaluation of an algoritm for computer analysis of maternal heart rate during laborPublication . Pinto, Paula; Bernardes, João; Costa-Santos, Cristina; Amorim-Costa, CéliaBackground Maternal heart rate (MHR) recordings are morphologically similar and sometimes coincident with fetal heart rate (FHR) recordings and may be useful for maternal–fetal monitoring if appropriately interpreted. However, similarly to FHR, visual interpretation of MHR features may be poorly reproducible. Methods : A computer algorithm for on-line MHR analysis was developed based on a previously existing version for FHR analysis. Inter-observer and computer-observer agreement and reliability were assessed in 40 one-hour recordings obtained from 20 women during the last 2 h of labor. Agreement and reliability were evaluated for the detection of basal MHR, long-term variability (LTV), accelerations and decelerations, using proportions of agreement (PA) and Kappa statistic (K), with 95% confidence intervals (95% CI). Changes in MHR characteristics between the first and the second hour of the tracings were also evaluated. Results There was a statistically significant inter-observer and computer-observer agreement and reliability in estimation of basal MHR, accelerations, decelerations and LTV, with PA values ranging from 0.72 (95% CI: 0.62–0.79) to 1.00 (95% CI: 0.99 1.00), and K values ranging from 0.44 (95% CI: 0.28–0.60) to 0.89 (95% CI: 0.82–0.96). Therover, basal MHR, number of accelerations and LTV were significantly higher in the last hour of labor, when compared to the initial hour. Discussion The developed algorithm for on-line computer analysis of MHR recordings provided good to excellent computer-observer agreement and reliability. Moreover, it allowed an objective detection of MHR changes associated with labor progression, providing more information about the interpretation of maternal–fetal monitoring during labor.
- Computer analysis of maternal–fetal heart rate recordings during labor in relation with maternal–fetal attachment and prediction of newborn acidemiaPublication . Pinto, Paula; Costa-Santos, Cristina; Ayres-de-Campos, DiogoAbstract Objective: To assess combined maternal (MHR) and fetal heart rate (FHR) recordings during labor, in relation with maternal–fetal attachment and prediction of newborn acidemia.Study design: Fifty-nine simultaneous MHR and FHR recordings were acquired in the final minutes of labor. Computer analysis followed the FIGO guidelines with estimation of MHR and FHR baselines, accelerations, decelerations, short- (STV) and long-term variabilities. MHR and FHR characteristics, their differences and correlations were assessed in relation to labor progression and to newborn umbilical artery blood (UAB) pH lower than 7.15 and 7.20. To assess prediction of acidemia, areas under ROC curves (auROC) were calculated.Results: Progression of labor was associated with a significant increase in MHR accelerations and FHR decelerations both in the non-acidemic and acidemic fetuses (p50.01). At the same time there was an increase in MHR–FHR correlations and differences in accelerations and decelerations in acidemic fetuses. The auROC ranged between 0.50 for FHR accelerations and 0.77 for MHR baseline plus FHR STV. Conclusions: MHR and FHR respond differently during labor with signs of increased maternal– fetal attachment during labor progression in acidemic fetuses. Combined MHR–FHR analysis may help to improve prediction of newborn acidemia compared with FHR analysis alone.
- Electrocardiography versus photoplethysmography in assessment of maternal heart rate variability during laborPublication . Gonçalves, Hernâni; Pinto, Paula; Silva, Manuela; Ayres-de-Campos, Diogo; Bernardes, JoãoEvaluation of maternal heart rate (MHR) variability provides useful information on the maternal-fetal clinical state. Electrocardiography (ECG) is the most accurate method to monitor MHR but it may not always be available, and pulse oximetry using photoplethysmography (PPG) can be an alternative. In this study we compared ECG and PPG signals, obtained with conventional fetal monitors, to evaluate signal loss, MHR variability indices, and the ability of the latter to predict fetal acidemia and operative delivery.
- External Uterine Contractions Signal AnalysisPublication . Gonçalves, H; Pinto, Paula; Ayres-de-Campos, D; Bernardes, JoãoLabor dystocia is a major cause of operative delivery, which is associated with ncreased risks for both mother and fetus. We assessed linear and non-linear dynamics of external uterine contraction signals, in relation to labor progression and dystocia. Linear time domain, spectral and entropy methods were used to analyze external uterine contraction recordings obtained during the last two hours of labor, in 28 cases with normal and 27 cases with operative deliveries (forceps, vacuum or caesarean). Progression of labor was associated with a statistically significant increase in most linear time domain and spectral indices, both in normal and operative deliveries, whereas most entropy indices increased in normal deliveries, but did not change in operative deliveries. On the other hand, when compared with normal births, operative deliveries were associated with significantly increased entropy indices before the last hour of labor and significantly decreased (a probably associated) sympatho-vagal balance in the last hour of labor. Linear and non-linear analysis of external uterine contraction recordings may provide useful physiopathological and clinical information on the progression of labor and the diagnosis of dystocia.
- Simultaneous computerized analysis of maternal and heart rate recordings during laborPublication . Pinto, PaulaAlthough the use of cardiotocography monitoring in industrialized countries is widespread, and there is obviously an intimate relationship between the mother and the fetus during pregnancy, few studies have been published about the relationship between maternal heart rate (MHR) and fetal heart rate (FHR) during labor. The main objective of this thesis was to explore whether combined analysis of MHR and FHR could improve maternal and fetal monitoring during labor. To overcome the limitations and subjectivity of common visual analysis, we developed and validated a new computerized program for simultaneous MHR and FHR analysis based on a previously developed program for FHR analysis alone, supported in the International Federation of Gynaecology and Obstetrics (FIGO) guidelines for fetal monitoring (Chapter 2). Good to excellent computer-observer agreement and reliability were obtained, and the detection of MHR changes associated with labor progression were studied. In fact, the morphologic similarity and sometimes coincidence between MHR and FHR, and the well-known possibility of misinterpreting the MHR as FHR, lead us to the assessment of an algorithm to detect and delete MHR-FHR ambiguities (Chapter 3). Improvements in FHR tracing analysis were obtained, with a significant increase of FHR signal loss of 1% and 6%, in cases with minor and major ambiguities, respectively, as well as a significant decrease in FHR decelerations. Then, to accomplish our main objective, we explored the application of combined conventional (Chapter 4) and non-conventional (Chapter 5) computerized analysis of MHR and FHR recordings in the assessment of labor progression, fetal acidemia, and maternal-fetal attachment. With conventional analyses, the progression of labor was associated with a significant increase in MHR accelerations and FHR decelerations both in non-acidemic and acidemic fetuses (p<0.01). In acidemic fetuses, there was an increase in MHR-FHR correlations and differences in accelerations and decelerations with modest area under the ROC curve (auROC) results. With non-conventional analyses, the progression of labor was also associated with a significant increase in most MHR and FHR linear indices, whereas entropy indices decreased. The inclusion of MHR on bivariate analysis achieved sensitivity and specificity values of nearly 100% and 89.1%, respectively. These two studies represent the first combined MHR and FHR analysis in relation to labor progress and prediction of newborn acidemia. Finally, to study an easier and alternative method of acquiring MHR signals, we explored the use of pulse oximetry using photoplethysmography (PPG) as an alternative method to electrocardiography (ECG) (Chapter 6). The study has evidenced PPG as an alternative for MHR acquiring signal and monitoring during labor, when appropriate MHR variability indices and reference ranges are used. In conclusion, our exploratory studies suggest that combined MHR-FHR analysis may improve maternal-fetal monitoring during labor in several ways. More extensive studies are warranted.