Methods and devices for the management of term and preterm labor

Bioengineering and the cervix: The past, current, and future for addressing preterm birth

The uterine cervix plays two important but opposing roles during pregnancy - as a mechanical barrier that maintains the fetus for nine months and as a compliant structure that dilates to allow for the delivery of a baby. In some pregnancies, however, the cervix softens and dilates prematurely, leading to preterm birth. Bioengineers have addressed and continue to address the lack of reduction in preterm birth rates by developing novel technologies to diagnose, prevent, and understand premature cervical remodeling. This article highlights these existing and emerging technologies and concludes with open areas of research related to the cervix and preterm birth that bioengineers are currently well-positioned to address.

An Automatic Method for the Segmentation and Classification of Imminent Labor Contraction From Electrohysterograms

OBJECTIVE

Preterm birth is the first cause of perinatal morbidity and mortality. Despite continuous clinical routine improvements, the preterm rate remains steady. Moreover, the specificity of the early diagnosis stays poor as many hospitalized women for preterm delivery threat finally deliver at term. In this context, the use of electrohysterograms may increase the sensitivity and the specificity of early diagnosis of preterm labor.

METHODS

This paper proposes a clinical application of electrohysterogram processing for the classification of patients as prone to deliver within a week or later. The approach relies on non-linear correlation analysis for the contraction bursts extraction and uses computation of various features combined with the use of Gaussian mixture models for their classification. The method is tested on a new dataset of 68 records collected on women hospitalized for preterm delivery threat.

RESULTS

This paper presents promising results for the automatic segmentation of the contraction and a classification sensitivity, specificity, and accuracy of, respectively, 80.7%, 76.3%, and 76.2%.

CONCLUSION

These results are in accordance with the gold standards but have the advantage to be non-invasive and could be performed at home.

SIGNIFICANCE

Diagnosis of imminent labor is possible by electrohysterography recording and may help in avoiding over-medication and in providing better cares to at-risk pregnant women.

Use of Mueller matrix colposcopy in the characterization of cervical collagen anisotropy

Annually, about 15 million preterm infants are born in the world. Of these, due to complications resulting from their premature birth, about 1 million would die before the age of five. Since the high incidence of preterm birth (PTB) is partially due to the lack of effective diagnostic modalities, methodologies are needed to determine risk of PTB. We propose a noninvasive tool based on polarized light imaging aimed at measuring the organization of collagen in the cervix. Cervical collagen has been shown to remodel with the approach of parturition. We used a full-field Mueller matrix polarimetric colposcope to assess and compare cervical collagen content and structure in nonpregnant and pregnant women in vivo. Local collagen directional azimuth was used and a total of eight cervices were imaged.

Feasibility of Transabdominal Electrohysterography for Analysis of Uterine Activity in Nonpregnant Women

PURPOSE

Uterine activity plays a key role in reproduction, and altered patterns of uterine contractility have been associated with important physiopathological conditions, such as subfertility, dysmenorrhea, and endometriosis. However, there is currently no method to objectively quantify uterine contractility outside pregnancy without interfering with the spontaneous contraction pattern. Transabdominal electrohysterography has great potential as a clinical tool to characterize noninvasively uterine activity, but results of this technique in nonpregnant women are poorly documented. The purpose of this study is to investigate the feasibility of transabdominal electrohysterography in nonpregnant women.

METHODS

Longitudinal measurements were performed on 22 healthy women in 4 representative phases of the menstrual cycle. Twelve electrohysterogram-based indicators previously validated in pregnancy have been estimated and compared in the 4 phases of the cycle. Using the Tukey honest significance test, significant differences were defined for P values below .05.

RESULTS

Half of the selected electrohysterogram-based indicators showed significant differences between menses and at least 1 of the other 3 phases, that is the luteal phase.

CONCLUSION

Our results suggest transabdominal electrohysterography to be feasible for analysis of uterine activity in nonpregnant women. Due to the lack of a golden standard, this feasibility study is indirectly validated based on physiological observations. However, these promising results motivate further research aiming at evaluating electrohysterography as a method to improve understanding and management of dysfunctions (possibly) related to altered uterine contractility, such as infertility, endometriosis, and dysmenorrhea.

Comparison of electrohysterogram signal measured by surface electrodes with different designs: A computational study with dipole band and abdomen models

Non-invasive measurement of uterine activity using electrohysterogram (EHG) surface electrodes has been attempted to monitor uterine contraction. This study aimed to computationally compare the performance of acquiring EHG signals using monopolar electrode and three types of Laplacian concentric ring electrodes (bipolar, quasi-bipolar and tri-polar). With the implementation of dipole band model and abdomen model, the performances of four electrodes in terms of the local sensitivity were quantified by potential attenuation. Furthermore, the effects of fat and muscle thickness on potential attenuation were evaluated using the bipolar and tri-polar electrodes with different radius. The results showed that all the four types of electrodes detected the simulated EHG signals with consistency. That the bipolar and tri-polar electrodes had greater attenuations than the others, and the shorter distance between the origin and location of dipole band at 20 dB attenuation, indicating that they had relatively better local sensitivity. In addition, ANOVA analysis showed that, for all the electrodes with different outer ring radius, the effects of fat and muscle on potential attenuation were significant (all p < 0.01). It is therefore concluded that the bipolar and tri-polar electrodes had higher local sensitivity than the others, indicating that they can be applied to detect EHG effectively.

Waterproofing EMG Instrumentation

While still experimental, measurement of external uterine electromyographic (EMG) activity is a more sensitive and noninvasive method for measuring uterine contractility in human labor than the methods currently used in clinical practice. Hydrotherapy is purported to improve contractility in labor, yet there have been no reports of abdominal uterine EMG activity measured during immersion. To test telemetric EMG equipment and different waterproofing techniques under dry and immersed conditions, the authors recorded surface EMG activity from the abdominal muscles of 11 healthy, nonpregnant women, 22 to 51 years of age. After attaching one pair of electrodes to the skin on either side of the umbilicus and applying the waterproofing material, the authors tested the signal by asking participants to perform a short series of leg lifts while seated in a chair to evoke abdominal muscle contractions. They were then immersed to the chest in a hydrotherapy tub while performing two to three leg lifts over 60 s every 5 min for 60 min with 20 lb of weight suspended from their ankles to counteract the buoyancy effect of water. EMG activity was continuously recorded. They then repeated the dry-measures sequence. While waterproofing remained intact, EMG signals were essentially unchanged between dry and wet conditions. Of the 11 waterproofing applications tested, 10 failed at some point. In the data from the successful application, EMG signals in both channels exhibited stable baselines throughout and an absence of low-frequency artifact. The development of this technique allows for the recording of external uterine EMG activity during hydrotherapy. The authors have begun using it to investigate the effects of hydrotherapy on uterine contractility during human labor.

Vaginal electrohysterography: the design and preliminary evaluation of a novel device for uterine contraction monitoring in an ovine model (.)

OBJECTIVE

Tocodynamometry is the most common method of labor evaluation but most clinicians would agree it has limited utility before 26 weeks of gestation. The obesity epidemic has further reduced our ability to accurately detect uterine contractions using the tocodynamometer at any gestational age. We sought to design and test a novel contraction monitor that bypasses the maternal abdomen.

METHODS

An optimized version of an intravaginal electrohysterographic ring device was tested in an ovine model. The device and its methodology as well as the tocodynamometer were validated against the current gold standard uterine activity monitor, the intrauterine pressure catheter in six sheep at varying gestational ages.

RESULTS

Both the intravaginal ring device and the tocodynamometer correlated well with IUPC, r = 0.69 and 0.73, respectively (p < 0.001). The number of contractions detected by each monitor remained similar even after accounting for confounders.

CONCLUSIONS

These results suggest that uterine activity can be monitored from the vaginal interface in an ovine model and offers an alternative clinical tool for the detection of contractions in situations, in which tocodynamometry would be ineffective or intrauterine monitoring inappropriate.

Feasibility and analysis of bipolar concentric recording of electrohysterogram with flexible active electrode

The conduction velocity and propagation patterns of the electrohysterogram (EHG) provide fundamental information on the electrophysiological condition of the uterus. However, the accuracy of these measurements can be impaired by both the poor spatial selectivity and sensitivity to the relative direction of the contraction propagation associated with conventional disc electrodes. Concentric ring electrodes could overcome these limitations. The aim of this study was to examine the feasibility of picking up surface EHG signals using a new flexible tripolar concentric ring electrode (TCRE), and to compare these signals with conventional bipolar recordings. Simultaneous recording of conventional bipolar signals and bipolar concentric EHG (BC-EHG) were carried out on 22 pregnant women. Signal bursts were characterized and compared. No significant differences were found between the channels in either duration or dominant frequency in the Fast Wave High frequency range. Nonetheless, the high pass filtering effect of the BC-EHG recordings gave lower frequency content between 0.1 and 0.2 Hz. Although the BC-EHG signal amplitude was about 5-7 times smaller than that of bipolar recordings, a similar signal-to-noise ratio was obtained. These results suggest that the flexible TCRE is able to pick up uterine electrical activity and could provide additional information for deducing the uterine electrophysiological condition.

Automated conduction velocity analysis in the electrohysterogram for prediction of imminent delivery: a preliminary study

Background. Analysis of the electrohysterogram (EHG) is a promising diagnostic tool for preterm delivery. For the introduction in the clinical practice, analysis of the EHG should be reliable and automated to guarantee reproducibility. Study Goal. Investigating the feasibility of automated analysis of the EHG conduction velocity (CV) for detecting imminent delivery. Materials and Methods. Twenty-two patients presenting with uterine contractions (7 preterm) were included. An EHG was obtained noninvasively using a 64-channel high-density electrode grid. Contractions were selected based on the estimated intrauterine pressure derived from the EHG, the tocodynamometer, and maternal perception. Within the selected contractions, the CV vector was identified in two dimensions. Results. Nine patients delivered within 24 hours and were classified as a labor group. 64 contractions were analyzed; the average amplitude of the CV vector was significantly higher for the labor group, 8.65 cm/s ± 1.90, compared to the nonlabor group, 5.30 cm/s ± 1.47 (P < 0.01). Conclusion. The amplitude of the CV is a promising parameter for predicting imminent (preterm) delivery. Automated estimation of this parameter from the EHG signal is feasible and should be regarded as an important prerequisite for future clinical studies and applications.

Towards BirthAlert--A Clinical Device Intended for Early Preterm Birth Detection

Preterm birth causes 1 million infant deaths worldwide every year, making it the leading cause of infant mortality. Existing diagnostic tests such as transvaginal ultrasound or fetal fibronectin either cannot determine if preterm birth will occur in the future or can only predict the occurrence once cervical shortening has begun, at which point it is too late to reverse the accelerated parturition process. Using iterative and rapid prototyping techniques, we have developed an intravaginal proof-of-concept device that measures both cervical bioimpedance and cervical fluorescence to characterize microstructural changes in a pregnant woman's cervix in hopes of detecting preterm birth before macroscopic changes manifest in the tissue. If successful, such an early alert during this "silent phase" of the preterm birth syndrome may open a new window of opportunity for interventions that may reverse and avoid preterm birth altogether.

Automatic evaluation of progression angle and fetal head station through intrapartum echographic monitoring

Labor progression is routinely assessed through transvaginal digital inspections, meaning that the clinical decisions taken during the most delicate phase of pregnancy are subjective and scarcely supported by technological devices. In response to such inadequacies, we combined intrapartum echographic acquisitions with advanced tracking algorithms in a new method for noninvasive, quantitative, and automatic monitoring of labor. Aim of this work is the preliminary clinical validation and accuracy evaluation of our automatic algorithm in assessing progression angle (PA) and fetal head station (FHS). A cohort of 10 parturients underwent conventional labor management, with additional translabial echographic examinations after each uterine contraction. PA and FHS were evaluated by our automatic algorithm on the acquired images. Additionally, an experienced clinical sonographer, blinded regarding the algorithm results, quantified on the same acquisitions of the two parameters through manual contouring, which were considered as the standard reference in the evaluation of automatic algorithm and routine method accuracies. The automatic algorithm (mean error ± 2SD) provided a global accuracy of 0.9 ± 4.0 mm for FHS and 4° ± 9° for PA, which is far above the diagnostic ability shown by the routine method, and therefore it resulted in a reliable method for earlier identification of abnormal labor patterns in support of clinical decisions.

Abdominal electromyography in laboring and non-laboring pregnant women at term and its clinical implications

OBJECTIVE

To determine the patterns of uterine action potentials in laboring and non-laboring women at term using the non-invasive abdominal electromyography technique.

METHODS

One hundred pregnant women at term who fulfilled the inclusion criteria were enrolled in the study and equally divided into two groups. Group I consisted of 50 women in active labor, while group II included 50 women not in labor. After enrollment, the cardiotocograph was applied to all women. Abdominal electromyographic recording was started and for every burst of action potential, we measured the amplitude, frequency and duration of action potential. The results were tabulated and statistically analyzed.

RESULTS

Both groups were comparable in demographic characteristics. Four patterns of EMG were detected. The amplitude of action potentials was significantly higher in laboring compared to non-laboring women (77.44 ± 11.25 vs 13.71 ± 8.57, P < 0.001). Similar significantly longer durations of electrical bursts were also noted in laboring women (45.94 ± 8.77 vs 7.11 ± 4.68 s, P < 0.001). Specific electromyographic changes were noted in women passing from the non-laboring to laboring state and in women who required oxytocin augmentation during labor.

CONCLUSION

Abdominal electromyography may help to distinguish between women in true active labor from those who are not. It also may help to identify women who will enter into labor within 24-72 h and those who require augmentation of labor.

[Evolution of electrohysterogram signals synchronization according to term of pregnancy: interest for preterm labor diagnosis]

OBJECTIVES

Our study focuses on the analysis of the uterine electromyogram recorded on women during pregnancy. We were interested in evaluating the synchronization of this electrical signal at various terms in order to follow evolution of synchronization as labor approaches. This study attempts to deepen our understanding of the myometrial maturation close to labor and to provide reliable parameters for improving preterm labor diagnosis.

PATIENTS AND METHODS

We performed a prospective study by recording the electrical signals of physiological uterine contractions (causing no delivery) on 16 pregnant women. We then calculated the non-linear correlation coefficient h(2) to estimate synchronization between EMG signals collected for each contraction. We expressed the results by grouping synchronization values by class of term in order to study the evolution of this coefficient along gestation. This study has been approved by the ethical committee of our hospital.

RESULTS

Our results show a non-significant increase of the h(2) value along term. There is however a trend towards an increase of the synchronization of EMG signals as labor approaches but not enough to conclude definitively.

DISCUSSION AND CONCLUSION

With a confirmation of the increase of h(2) along term, the study of the synchronization of uterine electrical activity could be an important clue to support the notion of myometrial maturation close to labor. Synchronization analysis could also be a promising parameter for reliable diagnosis of preterm labor.

Vectorial analysis of the electrohysterogram for prediction of preterm delivery: a preliminary study

Electrophysiological measurement of uterine contractions, referred to as electrohysterogram (EHG), is potentially more informative than methods currently used during pregnancy for timely recognition of complications such as preterm labor. Unfortunately, EHG measurement and interpretation remain challenging. Recently, some attention has been dedicated to the analysis of the EHG propagation, which is hypothetically predictive of the delivery time. This hypothesis, though physiologically reasonable, has not been investigated yet. A dedicated maximum likelihood (ML) method has been proposed and validated for identifying the conduction velocity vector of single EHG spikes. This validated ML method is here employed for comparing the conduction velocity vector in two groups of pregnant women with uterine contractions that were prospectively classified as productive or unproductive contractions. The estimated conduction velocity vector showed significant differences in the two groups. The spikes extracted from those contractions eventually classified as unproductive showed a significantly lower conduction velocity amplitude (CV = 4.89 ± 1.19 cm.s(-1) vs CV = 8.63 ± 2.92 cm.s(-1)) and a higher occurrence of upward propagation relative to productive contractions. These results suggest that productive and unproductive uterine contractions are associated to significantly different properties of the conduction velocity vector, which is likely to be proven fundamental in predicting preterm delivery.

Two-dimensional estimation of the electrohysterographic conduction velocity

Propagation of action potentials (APs) through an adequate number of uterine muscle cells induces contraction of the uterus. Monitoring uterine contractions, as the first sign of labor, can provide important information on the course of pregnancy and delivery. Unfortunately, current monitoring methods are affected by serious limitations. The electrohysterogram (EHG), which is the noninvasive recording of the APs propagating through the uterine smooth muscle cells, is here analyzed as a potential alternative to current methods. We focus on estimating the conduction velocity (CV) of surface APs extracted from an EHG recorded in a multielectrode configuration. In this work, a two-dimensional, 64-channel, high density electrode grid is used. Maximum likelihood methods are employed for analyzing the EHG AP propagation in two dimensions. The use of different weighting strategies of the derived cost function is introduced to deal with poor interchannel signal similarity. The presented methods were evaluated by specific simulations proving the best weighting strategy to lead to an accuracy improvement of 58%. EHG measurements on women with uterine contractions confirmed the feasibility of the method by leading to values of conduction velocity within the expected physiological range.

Nifedipine-induced changes in the electrohysterogram of preterm contractions: feasibility in clinical practice

Objective. Evaluating changes in the power spectral density (PSD) peak frequency of the electrohysterogram (EHG) caused by nifedipine in women with preterm contractions. Methods. Calculation of the PSD peak frequency in EHG contraction bursts at different times of nifedipine treatment in women in gestational age 24 to 32 weeks with contractions. Results. A significant (P < .05) decrease of PSD peak frequency between EHG signals measured before and 15 minutes after administration of nifedipine. A significant (P < .05) decrease in PSD peak frequency comparing signals recorded within 24 hours after administration of nifedipine to signals 1 day after tocolytic treatment. A higher average PSD peak frequency for patients delivering within 1 week than that for patients delivering after 1 week from nifedipine treatment (P > .05). Conclusions. EHG signal analysis has great potential for quantitative monitoring of uterine contractions. Treatment with nifedipine leads to a shift to lower PSD peak frequency in the EHG signal.

Non-invasive transabdominal uterine electromyography correlates with the strength of intrauterine pressure and is predictive of labor and delivery

OBJECTIVE

The study was conducted to investigate whether the strength of uterine contractions monitored invasively by intrauterine pressure catheter could be determined from transabdominal electromyography (EMG) and to estimate whether EMG is a better predictor of true labor compared to tocodynamometry (TOCO).

STUDY DESIGN

Uterine EMG was recorded from the abdominal surface in laboring patients simultaneously monitored with an intrauterine pressure catheter (n = 13) or TOCO (n = 24). Three to five contractions per patient and corresponding electrical bursts were randomly selected and analyzed (integral of intrauterine pressure; integral, frequency, amplitude of contraction curve on TOCO; burst energy for EMG). The Mann-Whitney test, Spearman correlation and receiver operator characteristics (ROC) analysis were used as appropriate (significance was assumed at a value of p < 0.05).

RESULTS

EMG correlated strongly with intrauterine pressure (r = 0.764; p = 0.002). EMG burst energy levels were significantly higher in patients who delivered within 48 h compared to those who delivered later (median [25%/75%]: 96,640 [26,520-322,240] vs. 2960 [1560-10,240]; p < 0.001), whereas none of the TOCO parameters were different. In addition, burst energy levels were highly predictive of delivery within 48 h (AUC = 0.9531; p < 0.0001).

CONCLUSION

EMG measurements correlated strongly with the strength of contractions and therefore may be a valuable alternative to invasive measurement of intrauterine pressure. Unlike TOCO, transabdominal uterine EMG can be used reliably to predict labor and delivery.

Noninvasive estimation of the electrohysterographic action-potential conduction velocity

Electrophysiological monitoring of the fetal-heart and the uterine-muscle activity, referred to as an electrohysterogram, is essential to permit timely treatment during pregnancy. While remarkable progress is reported for fetal-cardiac-activity monitoring, the electrohysterographic (EHG) measurement and interpretation remain challenging. In particular, little attention has been paid to the analysis of the EHG propagation, whose characteristics might be predictive of the preterm delivery. Therefore, this paper focuses, for the first time, on the noninvasive estimation of the conduction velocity of the EHG-action potentials. To this end, multichannel EHG recording and surface high-density electrodes are used. A maximum-likelihood method is employed for analyzing the EHG-action-potential propagation in two dimensions. The use of different weighting strategies of the derived cost function is introduced to deal with the poor signal similarity between different channels. The presented methods were evaluated by specific simulations proving the best weighting strategy to lead to an accuracy improvement of 56.7%. EHG measurements on ten women with uterine contractions confirmed the feasibility of the method by leading to conduction velocity values within the expected physiological range.

Electrohysterographic conduction velocity estimation

Monitoring and analysis of the fetal-heart and the uterine-muscle activity, referred to as electrohysterogram (EHG), is essential to permit timely treatment during pregnancy. While remarkable progress is reported for monitoring of the fetal cardiac activity, the EHG measurement and interpretation remains challenging, and limited knowledge is available on the underlying physiological processes. In particular, little attention has been paid to the analysis of the EHG propagation, whose characteristics might indicate the presence of coordinated uterine contractions leading to intrauterine pressure increase. Therefore, this study focuses for the first time on the noninvasive estimation of the conduction velocity of EHG action potentials by means of multichannel EHG recording and surface high-density electrodes. A maximum likelihood algorithm, initially proposed for skeletal-muscle electromyog-raphy, is modified for the required EHG analysis. The use of clustering and weighting is introduced to deal with poor signal similarity between different channels. The presented methods were evaluated by specific simulations, proving the combination of weighting and clustering to be the most accurate method. A preliminary EHG measurement during labor confirmed the feasibility of the method. An extensive clinical validation will however be necessary to optimize the method and assess the relevance of the EHG conduction velocity for pregnancy monitoring.

Myometrium electromechanical modeling for internal uterine pressure estimation by electrohysterography

During delivery, quantitative information on the uterine activity can be provided by internal uterine pressure (IUP) recordings using an invasive intrauterine pressure catheter (IUPC). The electrohysterogram, which measures the electrical signal that drives the mechanical contraction of the uterine muscle and the consequent IUP increase, is recorded by electrodes placed on the abdomen. Recent work demonstrated the possibility of reliably estimating the IUP noninvasively by electrohysterographic (EHG) signal analysis. To further improve the accuracy of IUP estimates, we investigated the use of three nonlinear functions for modeling the relationship between the electrical activation measured by the EHG signal and the mechanical response of the uterine muscle. The feature employed for obtaining a first estimate of the IUP is the unnormalized first statistical moment of the EHG spectrum. The relationship between the extracted feature and the IUP is modeled by a second-order polynomial, a logarithmic, and an exponential function. For validation, the IUPC and the EHG signals were recorded on nine women in labor. A second-order polynomial model already provided estimates that are highly correlated with the IUPC signal (r = 0.73). However, the logarithmic model resulted to be the most accurate, especially in terms of root mean squared error (RMSE = 5.13 mmHg).

Modeling and identification of the electrohysterographic volume conductor by high-density electrodes

The surface electrohysterographic (EHG) signal represents the bioelectrical activity that triggers the mechanical contraction of the uterine muscle. Previous work demonstrated the relevance of the EHG signal analysis for fetal and maternal monitoring as well as for prognosis of preterm labor. However, for the introduction in the clinical practice of diagnostic and prognostic EHG techniques, further insights are needed on the properties of the uterine electrical activation and its propagation through biological tissues. An important contribution for studying these phenomena in humans can be provided by mathematical modeling. A five-parameter analytical model of the EHG volume conductor and the cellular action potential (AP) is proposed here and tested on EHG signals recorded by a grid of 64 high-density electrodes. The model parameters are identified by a least-squares optimization method that uses a subset of electrodes. The parameters representing fat and abdominal muscle thickness are also measured by echography. The mean correlation coefficient and standard deviation of the difference between the echographic and EHG estimates were 0.94 and 1.9 mm, respectively. No bias was present. These results suggest that the model provides an accurate description of the EHG AP and the volume conductor, with promising perspectives for future applications.

Cervical ripening and insufficiency: from biochemical and molecular studies to in vivo clinical examination

To understand cervical ripening and especially the pathophysiology of cervical insufficiency, it is important to know the cervical composition: the cervix is dominated by fibrous connective tissue, consisting predominantly of Type I collagen (70%). Despite many studies of the cervix, we still rely upon relatively crude methods for clinical evaluation of the cervix. If the amount of cervical collagen plays a role in cervical insufficiency and in success of or length of induction of labor, then measurements of cervical collagen may provide an objective means of establishing the diagnosis or prognosis. We have established and reported a non-invasive means, called Collascope, to measure collagen cross-linking using light-induced fluorescence (LIF), and which is specifically designed to assess cervical ripening, and functions by measuring the natural fluorescence of non-soluble collagen in the cervix. Studies conducted in animals and humans in a variety of settings indicate that cervical function can be successfully monitored using the Collascope during pregnancy: LIF correlates negatively with gestational age and positively with time-to-delivery interval, and is predictive of delivery within 24h. Additionally LIF is significantly lower in women with cervical insufficiency. We suggest that the Collascope might be useful to better define management in cases of spontaneous preterm or induced term cervical ripening. From our studies and others, it is clear that in forecasting (pre-)term cervical ripening, the capability of the technologies and bioassays that have been generally accepted into clinical practice are limited. Any devices shown to be superior to the clinically accepted tests currently used should be quite useful for clinicians. The Collascope offers an objective measurement of both the function and state of the cervix, by directly measuring collagen cross-linking using LIF.

Parturition in domestic animals: targets for future research

Contents Compared with other parts of the reproductive cycle, the parturition process of domestic animals has received relatively little attention from researchers during the last two decades. Yet, interventions during parturition, either by the owner or the veterinarian, are frequently judged necessary and perinatal losses in most of the domestic species are (still) rather high. The present paper focuses on the birth process in three domestic species, the dog, pig and cow, mainly because most of the experimental and research work of the authors themselves was dealing with these three species. Against the background of specific clinical problems, breeding circumstances and economic performance, selected topics and questions are addressed to identify areas for future research. These are, among others, related to the mechanisms that trigger the birth process (are the foetuses involved in the dog and sow?), the role of hormones and cytokines during ripening of the cervix (activation and/or de-activation of specific matrix metallo-proteinases and their local inhibitors), the functional significance of fetal body movements to prepare the foetus for expulsion, and the exact time course of events involved in the transportation of an individual foetus from its intrauterine location, via the pelvic canal, to the outside world. Research on some of these topics, such as the ripening of the cervix in cows, might also contribute to resolve clinical problems in human obstetrics.

Challenge with ovalbumin antigen increases uterine and cervical contractile activity in sensitized guinea pigs

OBJECTIVE

The aims of this study were to investigate the effects of ovalbumin challenge on uterine and cervical contractility, intrauterine pressure, and uterine electromyography activity in sensitized guinea pigs.

STUDY DESIGN

Guinea pigs were sensitized by injection of ovalbumin-aluminum hydroxide suspension. Control animals were injected with the aluminum hydroxide suspension only. On days 55-57 of pregnancy, longitudinal uterine and cervical strips from guinea pigs were prepared for isometric tension recording. Nonpregnant guinea pigs were outfitted with telemetric transducers to record intrauterine pressure and uterine electromyography.

RESULTS

Ovalbumin significantly increased contractility of uterine and cervical strips from sensitized versus nonsensitized animals. These effects were abolished by histamine H(1) receptor antagonist in uterine strips and by histamine H(1) receptor antagonist and a mast cell stabilizer in cervical strips from sensitized animals. Cyclooxygenase and 5-lipoxygenase inhibitors had no significant effect on the response to ovalbumin. Treatment with ovalbumin in vivo significantly increased intrauterine pressure and uterine electromyography activity in sensitized but not in nonsensitized, animals.

CONCLUSION

Our findings indicate that type I hypersensitivity reactions may be important in mediating uterine contractility in pregnant and nonpregnant states.

Electrical impedance spectroscopy of the cervix in non-pregnant and pregnant women

OBJECTIVES

We sought to validate and measure the electrical impedance of the uterine cervix in non-pregnant and pregnant women by spectroscopy.

STUDY DESIGN

Cervical stromal impedance (CSI) was measured in 50 non-pregnant, 20 1st, 20 2nd and 50 3rd trimester pregnant women. The technique was also validated by comparing in vivo data to a finite element (FE) model of cervical tissue.

RESULTS

CSI agreed well with the FE model and was highly reproducible in all study groups. Mean (S.E.) CSI at 4-819 kHz was higher in pregnant (2.78 +/- 0.09 Omega m) compared to non-pregnant (2.38 +/- 0.07, p < 0.01) women, and in the 3rd trimester (3.08 +/- 0.13) compared to non-pregnant (p < 0.01), 1st trimester (2.42 +/- 0.12, p < 0.001) and 2nd trimester (2.20 +/- 0.05, p < 0.001) pregnant women.

CONCLUSION

Measurement of CSI provides a non-invasive method of assessing cervical tissue characteristics. Cervical extracellular matrix synthesis and leukocyte infiltration may account for the increased tissue impedance noted in the 3rd trimester.

Effects of nitric oxide and prostacyclin on hemodynamic response by big endothelin-1 in near term fetal sheep

AIMS

To measure plasma concentrations of endothelin (ET)-1, NO metabolites (nitrate/nitrite; NOx) and 6-keto PGF1 alpha (PGF1 alpha) in maternal and fetal sheep blood, and to evaluate the effects of big ET-1 on hemodynamic response, blood gases and NO and 6-keto PGF1 alpha production in near term fetal sheep.

METHODS

Hemodynamic parameters were measured during infusion of big ET-1 into the carotid vein in chronically catheterized fetal sheep on day 125 of gestation. Fetal arterial blood samples were obtained for ET-1, PGF1 alpha) and nitrate/nitrite (NOx) measurements.

RESULTS

ET-1, NOx and PGF1 alpha plasma concentrations were all significantly higher in fetal compared with the maternal plasma. Big ET-1 significantly decreased fetal systolic and diastolic blood pressure and significantly increased fetal heart rate. Big ET-1 stimulated plasma PGF1 alpha), but not NOx , concentration.

CONCLUSIONS

Circulatory regulating factors in the fetus were up-regulated. The effects of ET-1 on fetal hemodynamic response may be mediated via prostacyclin, but not via the NO pathway.

Cervical light-induced fluorescence in humans decreases throughout gestation and before delivery: Preliminary observations

OBJECTIVE

The purpose of this study was to investigate gestational changes of cervical light-induced fluorescence, an index of cross-linked collagen, and the relationship between light-induced fluorescence and the time-to-delivery interval.

STUDY DESIGN

Fifty patients were included in one of two groups. (1) Twenty-one healthy pregnant women without signs of labor underwent repeated cervical light-induced fluorescence measurement during the last trimester. (2) Light-induced fluorescence was measured in 29 patients with signs of labor, and the time from measurement to delivery was noted. Cervical light-induced fluorescence was obtained noninvasively with a prototype instrument that was designed specifically for this purpose. Spearman correlation and the Student t test and receiver-operator characteristics analysis were performed (P <.05).

RESULTS

Light-induced fluorescence correlated negatively with gestational age and positively with time-to-delivery interval, was significantly lower in patients who were delivered <24 hours compared with those patients who were delivered >24 hours later, and was predictive of delivery within 24 hours.

CONCLUSION

Cervical light-induced fluorescence decreases significantly as gestational age increases. Light-induced fluorescence may be a useful tool to identify patients in whom delivery is imminent.