Electrohysterographic characterization of the uterine myoelectrical response to labor induction drugs

Multi-channel electrohysterography enabled uterine contraction characterization and its effect in delivery assessment

Uterine contractions are routinely monitored by tocodynamometer (TOCO) at late stage of pregnancy to predict the onset of labor. However, TOCO reveals no information on the synchrony and coherence of contractions, which are important contributors to a successful delivery. The electrohysterography (EHG) is a recording of the electrical activities that trigger the local muscles to contract. The spatial-temporal information embedded in multiple channel EHG signals make them ideal for characterizing the synchrony and coherence of uterine contraction. To proceed, contractile time-windows are identified from TOCO signals and are then used to segment out the simultaneously recorded EHG signals of different channels. We construct sample entropy SamEn and Concordance Correlation based feature ψ from these EHG segments to quantify the synchrony and coherence of contraction. To test the effectiveness of the proposed method, 122 EHG recordings in the Icelandic EHG database were divided into two groups according to the time difference between the gestational ages at recording and at delivery (TTD). Both SamEn and ψ show clear difference in the two groups (p<10-5) even when measurements were made 120 h before delivery. Receiver operating characteristic curve analysis of these two features gave AUC values of 0.834 and 0.726 for discriminating imminent labor defined with TTD ≤ 24 h. The SamEn was significantly smaller in women (0.1433) of imminent labor group than in women (0.3774) of the pregnancy group. Using an optimal cutoff value of SamEn to identify imminent labor gives sensitivity, specificity, and accuracy as high as 0.909, 0.712 and 0.743, respectively. These results demonstrate superiority in comparing to the existing SOTA methods. This study is the first research work focusing on characterizing the synchrony property of contractions from the electrohysterography signals. Despite the very limited dataset used in the validation process, the promising results open a new direction to the use of electrohysterography in obstetrics.

Assessing uterine electrophysiology prior to elective term induction of labor

OBJECTIVE

The purpose of this study was to determine if uterine electrophysiological signals gathered from 151 non-invasive biomagnetic sensors spread over the abdomen were associated with successful induction of labor (IOL).

STUDY DESIGN

Uterine magnetomyogram (MMG) signals were collected using the SARA (SQUID Array for Reproductive Assessment) device from 33 subjects between 37 and 42 weeks gestational age. The signals were post-processed, uterine contractile related MMG bursts were detected, and parameters in the time and frequency domain were extracted. The modified Bishop score calculated at admission was used to determine the method of IOL. Wilcoxon's rank-sum test was used to compare IOL successes and failures for differences in gestational age (GA), parity, modified Bishop's score, maximum oxytocin, and electrophysiological parameters extracted from MMG.

RESULTS

The average parity was three times (3x) higher (1.53 versus 0.50; p = 0.039), and the average modified Bishop score was 2x higher (3.32 versus 1.63; p = 0.032) amongst IOL successes than failures, while the average GA and maximum oxytocin showed a small difference. For the MMG parameters, successful IOLs had, on average, 3.5x greater mean power during bursts (0.246 versus 0.070; p = 0.034) and approximately 1.2x greater mean number of bursts (2.05 versus 1.68; p = 0.036) compared to the failed IOLs, but non-significant differences were observed in mean peak frequency, mean burst duration, and mean duration between bursts.

CONCLUSION

The study showed that inductions of labor that took less than 24 h to deliver have a higher mean power in the baseline electrophysiological activity of the uterus when recorded prior to planned induction. The results are indicative that baseline electrophysiological activity measured prior to induction is associated with successful induction.

Uterus Modeling from Cell to Organ Level: towards Better Understanding of Physiological Basis of Uterine Activity

The relatively limited understanding of the physiology of uterine activation prevents us from achieving optimal clinical outcomes for managing serious pregnancy disorders such as preterm birth or uterine dystocia. There is increasing awareness that multi-scale computational modeling of the uterus is a promising approach for providing a qualitative and quantitative description of uterine physiology. The overarching objective of such approach is to coalesce previously fragmentary information into a predictive and testable model of uterine activity that, in turn, informs the development of new diagnostic and therapeutic approaches to these pressing clinical problems. This article assesses current progress towards this goal. We summarize the electrophysiological basis of uterine activation as presently understood and review recent research approaches to uterine modeling at different scales from single cell to tissue, whole organ and organism with particular focus on transformative data in the last decade. We describe the positives and limitations of these approaches, thereby identifying key gaps in our knowledge on which to focus, in parallel, future computational and biological research efforts.

Phase Entropy Analysis of Electrohysterographic Data at the Third Trimester of Human Pregnancy and Active Parturition

Phase Entropy (PhEn) was recently introduced for evaluating the nonlinear features of physiological time series. PhEn has been demonstrated to be a robust approach in comparison to other entropy-based methods to achieve this goal. In this context, the present study aimed to analyze the nonlinear features of raw electrohysterogram (EHG) time series collected from women at the third trimester of pregnancy (TT) and later during term active parturition (P) by PhEn. We collected 10-min longitudinal transabdominal recordings of 24 low-risk pregnant women at TT (from 35 to 38 weeks of pregnancy) and P (>39 weeks of pregnancy). We computed the second-order difference plots (SODPs) for the TT and P stages, and we evaluated the PhEn by modifying the k value, a coarse-graining parameter. Our results pointed out that PhEn in TT is characterized by a higher likelihood of manifesting nonlinear dynamics compared to the P condition. However, both conditions maintain percentages of nonlinear series higher than 66%. We conclude that the nonlinear features appear to be retained for both stages of pregnancy despite the uterine and cervical reorganization process that occurs in the transition from the third trimester to parturition.

A Comparative Study of Vaginal Labor and Caesarean Section Postpartum Uterine Myoelectrical Activity

Postpartum hemorrhage (PPH) is one of the major causes of maternal mortality and morbidity worldwide, with uterine atony being the most common origin. Currently there are no obstetrical techniques available for monitoring postpartum uterine dynamics, as tocodynamometry is not able to detect weak uterine contractions. In this study, we explored the feasibility of monitoring postpartum uterine activity by non-invasive electrohysterography (EHG), which has been proven to outperform tocodynamometry in detecting uterine contractions during pregnancy. A comparison was made of the temporal, spectral, and non-linear parameters of postpartum EHG characteristics of vaginal deliveries and elective cesareans. In the vaginal delivery group, EHG obtained a significantly higher amplitude and lower kurtosis of the Hilbert envelope, and spectral content was shifted toward higher frequencies than in the cesarean group. In the non-linear parameters, higher values were found for the fractal dimension and lower values for Lempel-Ziv, sample entropy and spectral entropy in vaginal deliveries suggesting that the postpartum EHG signal is extremely non-linear but more regular and predictable than in a cesarean. The results obtained indicate that postpartum EHG recording could be a helpful tool for earlier detection of uterine atony and contribute to better management of prophylactic uterotonic treatment for PPH prevention.

Tachysystole and risk of cesarean section after labor induction using misoprostol: A cohort study

OBJECTIVES

To investigate if tachysystole was associated with an increased risk of cesarean section or unfavorable maternal or neonatal outcomes following induction of labor by misoprostol vaginal inserts.

STUDY DESIGN

We conducted a retrospective cohort study of 446 women over 37 weeks of gestation admitted for labor induction by misoprostol vaginal inserts between May 2016 and May 2017. Fetal heart rate and uterine activity tracings were assessed for tachysystole, defined as ≥ 6 contractions per 10 min, averaged over a 30-minute window. Univariate analysis was performed by using t-test and Chi-square, comparing demographics, pregnancy characteristics, intrapartum monitoring, mode of delivery, neonatal outcomes (Apgar score < 7 at 5 min, umbilical cord artery pH < 7.10, neonatal intensive care unit admission) and maternal outcomes, with regard to the presence of tachysystole. The association between tachysystole and cesarean section was evaluated after adjusting for potential confounders by a modified Poisson regression model, expressed as an adjusted risk ratio and 95 % confidence intervals.

RESULTS

A total of 140 women (31.4 %) presented with tachysystole. The median duration of tachysystole was 2 h 12 min. The rate of cesarean section was 25.0 % (N = 35) among patients with tachysystole and 19.6 % (N = 60) for those without tachysystole. Presence of tachysystole during induction of labor with misoprostol vaginal inserts was not associated with cesarean section (adjusted risk ratio,1.0; 95 % confidence interval, 0.7-1.4). Neonatal and maternal outcomes were similar between mothers who did and did not experience tachysystole.

CONCLUSIONS

This study illustrates that tachysystole is not associated with an increased risk of cesarean section after induction of labor by misoprostol vaginal inserts. The impact of excessive uterine activity on the fetal wellbeing defined by the frequency of uterine contraction alone is probably insufficient. Further research on the development of accurate measures of uterine contractility is necessary to better understand its effect on fetal well-being.

Potential use of electrohysterography in obstetrics: a review article

Monitoring the uterine contraction during pregnancy is necessary to monitor labor progress, fetal and maternal well-being, and uterine activity. The aim of this review was to evaluate the performance of electrohysterography and to analyze the nature of uterine contraction. A search was undertaken using PubMed, Embase, and ClinicalTrials.gov database from 1 January 1950 to 1 November 2018. Search terms include: "Uterine" or "Uterus" or "Labor" or "Labour" and "electrical activity" or "electrohysterogram" or "electrohysterograph". Reviewing the literature, electrohysterography showed a higher sensitivity for uterine contraction detection and was independent of body mass index, abdominal wall thickness, or maternal position enabling monitoring obese patients as well. Electrohysterography can enhance uterine monitoring throughout labor because of its noninvasiveness, adhesive properties, and reduced obesity sensitiveness. Electrohysterography should be available to safely improve intrapartum monitoring instead of the invasive intrauterine pressure catheter.