Cervical Evaluation: From Ancient Medicine to Precision Medicine

Elasticity of the Cervix in Relation to Uterus Position

Strain elastography allows the evaluation of tissue elasticity. Background/Objectives: Tissue elasticity depends on the content and distribution of collagen fibers and is shaped by the applied tensile forces that may differ in uteri with a different angle of flexion of the corpus on the cervix. The objective was to investigate whether the angle of uterine flexion is related to cervical tissue elasticity. Methods: The anterior angle between the longitudinal axis of the uterus corpus and that of the cervix was measured in 275 non-pregnant young women by transvaginal ultrasonography and considered both as an absolute value or categorized as ≤150°, between >150° and ≤210°, and >210°. Strain elastography was used to assess tissue elasticity by placing the probe in the anterior vaginal fornix. Tissue elasticity was evaluated in the middle of the anterior cervical compartment (ACC), in the middle of the posterior cervical compartment (PCC), in the middle portion of the cervical canal (MCC), and at the internal cervical os (ICO). In a sagittal plane MCC was evaluated across the cervical canal, and ACC and PCC at a distance equal between the cervical canal and the outer anterior or posterior part of the cervix. MCC, ACC and PCC were evaluated at equal distance between the ICO and the external cervical os. Elasticity was expressed as a color score ranging from 0.1 (low elasticity) to 3 (high elasticity). Results: The angle of uterine flexion show a negative linear relation with the elasticity of the ACC (p = 0.001) and MCC (p = 0.002) and a positive relation with the elasticity of the PCC (p = 0.054). In comparison to uteri with an angle of flexion of <150°, those with an angle of flexion of >210° had lower elasticity of the ACC (p = 0.001) and MCC (p = 0.001) and higher elasticity of the PCC (p = 0.004). The ACC/PCC and PCC/MCC elasticity ratios were also significantly different (p = 0.001). Conclusions: The angle of uterine flexion is associated with changes in cervix elasticity. Retroflexion is associated with stiffer ACC and MCC and a more elastic PCC. Differences in tissue elasticity suggest structural changes of the cervix that may have implication in variate obstetric and gynecological conditions.

Predicting Spontaneous Labor beyond 39 Weeks among Low-Risk Expectantly Managed Pregnant Patients

OBJECTIVES

The aim of the study was to identify the characteristics associated with spontaneous labor onset in pregnant patients undergoing expectant management at greater than 39 weeks' gestation and delineate perinatal outcomes associated with spontaneous labor compared with labor induction.

STUDY DESIGN

This was a retrospective cohort study of singleton pregnancies at ≥390/7 weeks' gestation delivered at a single center in 2013. The exclusion criteria were elective induction, cesarean delivery or presence of a medical indication for delivery at 39 weeks, more than one prior cesarean delivery, and fetal anomaly or demise. We evaluated prenatally available maternal characteristics as potential predictors of the primary outcome-spontaneous labor onset. Multivariable logistic regression was used to generate two parsimonious models: one with and one without third trimester cervical dilation. We also performed sensitivity analysis by parity and timing of cervical examination, and compared the mode of delivery and other secondary outcomes between patients who went into spontaneous labor and those who did not.

RESULTS

Of 707 eligible patients, 536 (75.8%) attained spontaneous labor and 171 (24.2%) did not. In the first model, maternal body mass index (BMI), parity, and substance use were identified as the most predictive factors. Overall, the model did not predict spontaneous labor (area under the curve [AUC]: 0.65; 95% confidence interval [CI]: 0.61-0.70) with high accuracy. The addition of third trimester cervical dilation in the second model did not significantly improve labor prediction (AUC: 0.66; 95% CI: 0.61-0.70; p = 0.76). These results did not differ by timing of cervical examination or parity. Patients admitted in spontaneous labor had lower odds of cesarean delivery (odds ratio [OR]: 0.33; 95% CI: 0.21-0.53) and neonatal intensive care unit (NICU) admission (OR: 0.38; 95% CI: 0.15-0.94). Other perinatal outcomes were similar between the groups.

CONCLUSION

Maternal characteristics did not predict spontaneous labor onset at ≥39 weeks' gestation with high accuracy. Patients should be counseled on the challenges of labor prediction regardless of parity and cervical examination, outcomes if spontaneous labor does not occur, and benefits of labor induction.

KEY POINTS

· Majority of patients will attain spontaneous labor at ≥39 weeks.. · Maternal characteristics do not predict labor at ≥39 weeks.. · Spontaneous labor has associated lower perinatal risks.. · A shared decision model should be utilized in counseling patients who may choose expectant management..

A Rational and Standardized Prenatal Examination

Importance

As prenatal care is in transition after the COVID-19 pandemic, reviewing fundamental physical examination approaches is necessary for providers examining obstetrical patients.

Objective

The objective of this review is 3-fold: (1) convey why the age of telemedicine necessitates reconsideration of the standardized physical examination in routine prenatal care; (2) identify the screening efficacy of examination maneuvers used within a standard prenatal examination of the neck, heart, lungs, abdomen, breasts, skin, lower extremities, pelvis, and fetal growth; and (3) propose an evidence-based prenatal physical examination.

Evidence Acquisition

A comprehensive literature review identified relevant research, review articles, textbook chapters, databases, and societal guidelines.

Results

We conclude that an evidence-based prenatal examination for asymptomatic patients includes the following maneuvers: inspection and palpation for thyromegaly and cervical lymphadenopathy, cardiac auscultation, fundal height measurement, and a pelvic examination for purposes including testing for gonorrhea and chlamydia, assessing pelvimetry, and assessing cervical dilation later in the pregnancy, intrapartum, or in the setting of ultrasonogram-detected prelabor preterm cervical shortening.

Conclusions and Relevance

Although not true of all physical examination maneuvers, this article demonstrates that there are maneuvers that continue to play important screening roles in asymptomatic patients. With the increase in virtual visits and fewer in-person prenatal appointments, the rational basis for maneuvers recommended in this review should inform decision making around the prenatal examination performed.

Engineering high throughput screening platforms of cervical cancer

Cervical cancer is the second leading cause of cancer-related death in women under 40 and is one of the few cancers to have an increased incidence rate and decreased survival rate over the last 10 years. One in five patients will have recurrent and/or distant metastatic disease and these patients face a 5-year survival rate of less than 17%. Thus, there is a pressing need to develop new anticancer therapeutics for this underserved patient population. However, the development of new anticancer drugs remains a challenge, as only 7% of novel anticancer drugs are approved for clinical use. To facilitate identification of novel and effective anticancer drugs for cervical cancer, we developed a multilayer multicellular platform of human cervical cancer cell lines and primary human microvascular endothelial cells that interfaces with high throughput drug screening methods to evaluate the anti-metastatic and anti-angiogenic drug efficacy simultaneously. Through the use of design of experiments statistical optimization, we identified the specific concentrations of collagen I, fibrinogen, fibronectin, GelMA, and PEGDA in each hydrogel layer that maximized both cervical cancer invasion and endothelial microvessel length. We then validated the optimized platform and assessed its viscoelastic properties. Finally, using this optimized platform, we conducted a targeted drug screen of four clinically relevant drugs on two cervical cancer cell lines. Overall, this work provides a valuable platform that can be used to screen large compound libraries for mechanistic studies, drug discovery, and precision oncology for cervical cancer patients.

Measurement of cervical softness before cerclage placement with an aspiration-based device

BACKGROUND

An abnormally soft cervix could contribute to the pathophysiology of cervical shortening and cervical insufficiency. Multiple techniques to measure cervical softness have been developed but none are used routinely in clinical practice. A clinically acceptable technique to measure cervical softness could improve identification of patients at risk for cervix-related preterm birth.

OBJECTIVE

This study aimed to measure cervical softness in patients with cervical insufficiency and in normal controls using a novel, aspiration-based device. We hypothesized that the cervix is softer in patients with cervical insufficiency.

STUDY DESIGN

This was a cross-sectional study of patients presenting for cerclage at a single academic medical center. Cervical softness was measured using a noninvasive, aspiration-based device placed on the anterior lip of the cervix during a speculum examination. The device measured the aspiration pressure required to displace cervical tissue to a predefined deformation level. Stiff tissue required increased aspiration pressure, whereas soft tissue required lower pressure values. Cerclage patients were subdivided into 3 groups, namely history-indicated, ultrasound-indicated, and examination-indicated cerclage. Controls were healthy volunteers between 12+0 weeks and 23+6 weeks of gestation without a history of cervical insufficiency and were matched by gestational age to the patients in the cerclage groups. Women with a cerclage in place, multiple gestations, active genital infection, or previous cervical excision procedures were excluded. Delivery information was subsequently recorded as well.

RESULTS

Data from 133 women were analyzed; of those, 54 patients were in the cerclage group (23 history-indicated, 12 ultrasound-indicated, and 19 examination-indicated participants) and 79 were controls (40 in the first trimester and 39 in the second trimester groups). Patients who presented for ultrasound-indicated cerclage had significantly softer cervices (median; interquartile range) than second trimester controls (62 mbar; 50.5-114 vs 81 mbar; 75-101; P=.042). The difference in cervical softness was not significantly different between the history-indicated and examination-indicated cerclage groups and their respective control groups.

CONCLUSION

Patients presenting for ultrasound-indicated cerclage had significantly softer cervices than normal controls as measured by an aspiration-based device. Quantitative measurement of cervical softness with the aspiration-based device is a promising technique for objective measurement of cervical softness during pregnancy.

When standard measurement meets messy genitalia: Lessons from 20th century phallometry and cervimetry

This paper examines two episodes in the history and philosophy of phallometry and cervimetry in the second half of the 20th century. Phallometry is the measurement of the human penis with special devices (phallometers) in a psychophysiological context, while cervimetry is the measurement of the cervix in laboring women (by hand or by cervimeter). Despite decades of efforts to standardize these measuring practices, we still have only non-standard ways of measuring the dynamics of the cervix during labor as well as penile tumescence during arousal. We adopt the lens of "messiness" as an analytic tool in order to trace historical actors' methodological assumptions, goals, and decisions that were involved in their measuring practices. It will be argued that, far from being an a priori attribute, the "messiness" of biomedical phenomena (and how to best respond to it) depends on the actors' methodological priorities. What is "messy" is actively shaped (and re-shaped) by researchers' instrumental assumptions and theoretical commitments, as demonstrated in their method of measuring. This paper also offers a preview of early findings from our current research on the history of cervical measurement (Jackson) and phallic measurement (Wassermann). Drawing on primary source material we have analyzed, the argument will be developed in two parts. First, in the context of phallometry research: Two different and eventually diametrically opposed methodological approaches developed when confronted with "messy" human bodies and minds, a divergence which still exists today. Second, in the case of cervimetry research: "messiness" emerged when researchers tried to standardize the measurement of the human cervix, to no avail. Ironically, today's "messy" practice of measuring the cervix by hand has been continually justified by knowledge gained in the continued pursuit (and failure) of standardized replacements of this method.

Reliability of ultrasound versus digital vaginal examination in detecting cervical dilatation during labor: a diagnostic test accuracy systematic review

Background

This systematic review aimed to investigate the reliability of ultrasound method compared with digital vaginal examinations in detecting cervical dilation.

Methods

We searched Cochrane (CENTRAL), MEDLINE, EMBASE, CINAHL, ISI Web of Science Core Collection, Trip Database, PubMed, DARE and NHS EED, HTA, and PROSPERO. Ten observational studies with a total sample size of 856 were included in the meta-analysis.

Results

The intraclass correlation coefficient (ICC) values ranged between 0.21 and 0.69. The fixed-effect models for the ultrasound test showed an average of ICC (r = 0.32 (95% CI 0.26–0.38). Correlation between two methods was poor (r = 0.359, 95% CI 0.26–0.44). In nulliparous and multigravida participants the correlation between ultrasound measurements and digital examinations was (r = 0.349, 95% CI 0.25–0.43) and ICC (r = 0.676, 95% CI 0.419–0.833), respectively.

Conclusion

Trans-perineal ultrasonography seems to be a reliable method for assessing labor progression in multigravida women, but its usage in nulliparous women needs further studies.

Maternal health and pregnancy outcome in diagnosed and undiagnosed Marfan syndrome: A registry-based study

In Marfan syndrome (MFS), pregnancy is considered as high risk due to the deficiency of fibrillin in the connective tissue and increased risk of aortic dissection. The objective was to demonstrate the consequences on maternal health, in women with diagnosed and undiagnosed MFS at the time of pregnancy and childbirth. By using national health care registries, we identified all pregnancy related outcomes, from women with MFS (n = 183) and an age-matched background population (n = 18,300). We found 91 pregnancies during follow-up. Significantly fewer women with MFS gave birth, compared to the background population. No women with known MFS had a pregnancy related aortic dissection but complications related to the cervix were increased (HR:19.8 [95% CI:2.2-177.5]). Fifty women with MFS were undiagnosed at the time of their first pregnancy and/or childbirth. Among these, there were more birth canal related complications HR:27.2 (95% CI: 2.3-315.0), preeclampsia (HR:2.25 [95% CI: 1.11-4.60]), fetal deaths (HR:12.3 [95% CI: 1.51-99.8]), and all delivery-related dissections came from this subgroup. In conclusion, undiagnosed women with MFS experienced more pregnancy and childbirth related complications including fetal death, birth canal issues, preeclampsia, and aortic disease, which emphasizes the need for an early MFS diagnosis and special care during pregnancy and childbirth.

Shear wave dispersion as a potential biomarker for cervical remodeling during pregnancy: evidence from a non-human primate model

Shear wave dispersion (variation of phase velocity with frequency) occurs in tissues with layered and anisotropic microstructure and viscous components, such as the uterine cervix. This phenomenon, mostly overlooked in previous applications of cervical Shear Wave Elasticity Imaging (SWEI) for preterm birth risk assessment, is expected to change drastically during pregnancy due to cervical remodeling. Here we demonstrate the potential of SWEI-based descriptors of dispersion as potential biomarkers for cervical remodeling during pregnancy. First, we performed a simulation-based pre-selection of two SWEI-based dispersion descriptors: the ratio R of group velocities computed with particle-velocity and particle-displacement, and the slope S of the phase velocity vs. frequency. The pre-selection consisted of comparing the contrast-to-noise ratio (CNR) of dispersion descriptors in materials with different degrees of dispersion with respect to a low-dispersive medium. Shear waves induced in these media by SWEI were simulated with a finite-element model of Zener viscoelastic solids. The pre-selection also considered two denoising strategies to improve CNR: a low-pass filter with automatic frequency cutoff determination, and singular value decomposition of shear wave displacements. After pre-selection, the descriptor-denoising combination that produced the largest CNR was applied to SWEI cervix data from 18 pregnant Rhesus macaques acquired at weeks 10 (mid-pregnancy stage) and 23 (late pregnancy stage) of the 24.5-week full pregnancy. A maximum likelihood linear mixed-effects model (LME) was used to evaluate the dependence of the dispersion descriptor on pregnancy stage, maternal age, parity and other experimental factors. The pre-selection study showed that descriptor S combined with singular value decomposition produced a CNR 11.6 times larger than the other descriptor and denoising strategy combinations. In the Non-Human Primates (NHP) study, the LME model showed that descriptor S significantly decreased from mid to late pregnancy (-0.37 ± 0.07 m/s-kHz per week, p <0.00001) with respect to the base value of 15.5 ± 1.9 m/s-kHz. This change was more significant than changes in other SWEI features such as the group velocity previously reported. Also, S varied significantly between the anterior and posterior portions of the cervix (p =0.02) and with maternal age (p =0.008). Given the potential of shear wave dispersion to track cervical remodeling, we will extend its application to ongoing longitudinal human studies.

A new quantification system for assessing the degree of acute cervical insufficiency based on physical and sonographic examination

OBJECTIVES

Acute cervical insufficiency accounts for 10-25 % of all mid-trimester pregnancy losses. However, the definition and description for the degree of acute cervical insufficiency were obscure and different among the many studies. The aim of this study was to suggest a new 4-digit quantification system and to evaluate the outcome according to the new system in women with acute cervical insufficiency.

STUDY DESIGN

A retrospective cohort study was conducted in patients with acute cervical insufficiency who underwent physical examination indicated cervical cerclage. Acute cervical insufficiency was defined as painless external os dilation with prolapsed and/or visible membranes on speculum examination. The status of fetal membranes was described using two values: 1) size of the prolapsed membrane (P, measured using ultrasound); and 2) size of visible fetal membranes (M, evaluated by speculum examination). The status of cervix was described using two values: 1) dilatation of the narrowest os (O, measured by ultrasound); and 2) functional cervical length (C, measured by ultrasound). The patients were divided into 3 groups as follows: Stage I, patients with visible fetal membranes (M > 0) but with a remaining functional cervix (C > 0) (N = 7); stage II, those with visible fetal membranes (M > 0) and a functional cervical length of 0 but without prolapsed membranes (P = 0) (N = 33); and stage III, those with prolapsed membranes (P > 0) (N = 40).

RESULTS

1) Patients who delivered before 34 weeks of gestation had a significantly lower median gestational age at cerclage operation and a significantly higher median P, M, C values than those who delivered at or beyond 34 weeks of gestation(P < 0.01 for gestational age at operation, P and M values; P < 0.05 for C value); 2) The higher the stage based on PMOC quantification system, the greater the risk of preterm delivery before <24, <32, <34, and <37 weeks of gestation (P < 0.001 for all); 3) The neonatal survival rate was 100 % (7/7) for stage I, 93.9 % (31/33) for stage II, and 60 % (24/40) for stage III.

CONCLUSION

The PMOC system was a simple method to describe the individualized conditions and to predict the risk of preterm births in all spectrums of acute cervical insufficiency.

Aspiration technique-based device is more reliable in cervical stiffness assessment than digital palpation

Background

The purpose of this study was to compare the reliability and reproducibility of the traditional qualitative method of assessing uterine cervical stiffness with those of a quantitative method using a novel device based on the aspiration technique.

Methods

Five silicone models of the uterine cervix were created and used to simulate different cervical stiffnesses throughout gestation. The stiffness of the five cervix models was assessed both by digital palpation (firm, medium and soft) and with the Pregnolia System. Five self-trained participants conducted the device-based assessment, whereas 63 obstetricians and midwives, trained in digital palpation, conducted the cervical palpation.

Results

The results of the two methods were analyzed in terms of inter-and intra-observer variability. For digital palpation, there was no common agreement on the assessment of the stiffness, except for the softest cervix. When assessing the same cervix model for a second time, 76% of the obstetricians and midwives disagreed with their previous assessment. In contrast, the maximum standard deviation for the device-based stiffness assessment for intra- and inter-observer variability was 3% and 3.4%, respectively.

Conclusions

This study has shown that a device based on the aspiration technique provides obstetricians and midwives with a method for objectively and repeatably assess uterine cervical stiffness, which can eliminate the need to rely solely on a subjective interpretation, as is the case with digital palpation.

Sonoelastography for the comparative assessment of cervical maturation after different approaches to cervical preparation ahead of labor induction

Aim: To compare the efficacy of different approaches to cervical preparation to labor induction using the ultrasound cervical elastography.Materials and methods: This prospective open-label study included 200 pregnant women aged between 23 and 38 years eligible for labor pre-induction. Patients were divided into four groups (n = 50 per group). In Group I, four osmotic Dilapan-S cervical dilators combined with two doses of oral mifepristone (200 mg each) 24 h apart were used. The dilators were inserted for up to 12 h. In Group II, only the Dipalan-S dilators were used. In Group III, a Foley catheter was positioned intracervically for 12 h. In Group IV, we used two doses of intracervical prostaglandin E₂ gel (0.5 mg each) 6 h apart. Cervical maturation was assessed using the Bishop scoring system and the ultrasound cervicometry with the color mapping and calculation of SR ratio. At baseline, all participants were also divided into three subgroups depending on the Bishop score before the pre-induction. Subgroup А (n = 66) included patients with the Bishop score between 0‒2 points, subgroup B (n = 69) between 3-4 points, and subgroup С (n = 65) between 4-6 points.Results: Our study showed that the efficacy of Dilapan-S combined with mifepristone for cervical preparation to labor induction was higher than Dilapan-S, Foley catheter and intracervical prostaglandin E₂ gel. In this group, the Bishop score after the pre-induction was the highest (11.4 (0.21) points versus 10.2 (0.2), 9.4 (0.3) и 9.67 (0.25) in Groups II, III and IV respectively (p < .05 for all). The lowest SR values were also observed among the patients receiving the combination of Dilapan-S and mifepristone: 1.23 (0.04) versus 1.63 (0.07), 1.7 (0.08) and 1.83 (0.1) in Groups II, III and IV respectively (p < .05 for all). The sonoelastographic SR values in subgroups B and C were statistically lower compared with subgroup A across all groups studied. Ultrasound elastography of the cervix allowed to perform a more objective assessment of cervical maturation compared with the Bishop scoring.Conclusion: Dilapan-S combined with mifepristone had higher efficacy for cervical preparation to labor induction compared with other approaches investigated.

Quantitative elastography of cervical stiffness during the three trimesters of pregnancy with a semiautomatic measurement program: A longitudinal prospective pilot study

AIM

To assess the reproducibility of a semiautomatic quantification tool for cervical stiffness and evaluate the normal changes in cervical elasticity during the three trimesters of pregnancy.

METHODS

This longitudinal prospective pilot study evaluated cervical elasticity during the three trimesters of pregnancy (11-14, 20-24 and 28-32 weeks) in women with singleton pregnancies. Women with a history of conization, cerclage, cervical Naboth cysts (diameter > 10 mm), cervical tumors, or uterine malformation were excluded. A semiautomatic tool was used to evaluate the stiffness of the whole cervix and the internal and external cervical os with multiple quantitative elasticity parameters and the cervical length (CL) on the sagittal view via transvaginal elastography. Intraclass correlation coefficients (ICC) and Bland-Altman analysis were used to assess intra- and interobserver variability. E-Cervix parameters during the three trimesters were compared using the Friedman test.

RESULTS

In total, 217 women with 651 strain examinations during the three trimesters were included. The intra- and interobserver ICC for the E-Cervix parameters ranged from 0.947 to 0.991 and 0.855 to 0.989, respectively. There were significant differences in all parameters among the three trimesters. Cervical elasticity showed significant softening and became heterogeneous during the three trimesters. The median CL was significantly shorter in the first trimester than in the second and third trimesters (P = 0.004, P < 0.001).

CONCLUSION

E-Cervix provides a graphical tool for operators to easily define regions of interest and obtain multiple repeatable measures of elasticity. The normal references for E-Cervix parameters during the three trimesters reflect the physiological cervical changes during pregnancy.

Labour and delivery: a clinician's perspective on a biomechanics problem

Predicting how and when a pregnant woman will deliver her fetus has always been a problem for the clinician, and, consequently, there has been little progress made in preventing poor outcomes from pregnancies that deliver too soon or too late. In the opinion of the author, a maternal-fetal medicine specialist, rethinking labour within a biomechanical framework and studying it like an engineering problem could be a promising approach to unlocking the mysteries of labour.

Quantitative Ultrasound Parameters Based on the Backscattered Echo Power Signal as Biomarkers of Cervical Remodeling: A Longitudinal Study in the Pregnant Rhesus Macaque

Clinical prediction and especially prevention of abnormal birth timing, particularly pre-term, is poor. The cervix plays a key role in birth timing; it first serves as a rigid barrier to protect the developing fetus, then becomes the pathway to delivery of that fetus. Imaging biomarkers to define this remodeling process could provide insights to improve prediction of birth timing and elucidate novel targets for preventive therapies. Quantitative ultrasound (QUS) approaches that appear promising for this purpose include shear wave speed (SWS) estimation to quantify softness, as well as parameters based on backscattered power, such as the mean backscattered power difference (mBSPD) and specific attenuation coefficient (SAC), to quantify the organization of tissue microstructure. Invasive studies in rodents demonstrated that as pregnancy advances, cervical microstructure disorganizes as tissue softness and compliance increase. Our non-invasive studies in pregnant women and rhesus macaques suggested that QUS can detect these microstructural changes in vivo. Our previous study in the same cohort showed a progressive decline in SWS during pregnancy, consistent with increasing tissue softness, and we hypothesized that backscatter parameters would also decrease, consistent with increasing microstructural disorganization. In this study, we analyzed the mBSPD and SAC in the cervices of rhesus macaques (n = 18). We found that both mBSPD and SAC decreased throughout pregnancy (p < 0.001 for both parameters) and that the former appears to be a more reliable biomarker. In summary, biomarkers that can characterize tissue microstructural organization are promising for comprehensive characterization of cervical remodeling in pregnancy.

Quantitative Ultrasound Biomarkers Based on Backscattered Acoustic Power: Potential for Quantifying Remodeling of the Human Cervix during Pregnancy

As pregnancy progresses, the cervix remodels from a rigid structure to one pliable enough to allow delivery of a fetus, a process that involves progressive disorganization of cervical microstructure. Quantitative ultrasound biomarkers that may detect this process include those derived from the backscattered echo signal, namely, acoustic attenuation and backscattered power loss. We recently reported that attenuation and backscattered power loss are affected by tissue anisotropy and heterogeneity in the ex vivo cervix. In this study, we compared attenuation and backscattered power difference in a group of women in early pregnancy (first trimester) with those in a group in late pregnancy (third trimester). We observed a significant decrease in the backscattered power difference in late as compared with early pregnancy, suggesting decreased microstructural organization in late pregnancy, a finding that is consistent with animal models of cervical remodeling. In contrast, we found no difference in attenuation between the time points. These results suggest that the backscattered power difference, but perhaps not attenuation, may be a useful clinical biomarker of cervical remodeling.

Use of intrapartum ultrasound in term pregnant women with contractions before hospital admission

INTRODUCTION

The aim of this study was to test the hypothesis that transperineal ultrasound can be used to decide whether to admit a pregnant woman due to labor.

MATERIAL AND METHODS

In this analytical cross-sectional observational study, transperineal ultrasound was performed on pregnant women with intact membranes who came to the hospital due to contractions. A decision was made to admit women due to labor based on the ultrasound measurements. The ultrasound measurements were used to determine cervical dilation, the angle of progression, and fetal head position. The managing midwives were blinded to the results and made the final decision to admit the women based on digital vaginal examination.

RESULTS

It was possible to decide whether a woman had to be admitted for delivery or discharged due to the latent phase of labor according to the ultrasound examination in 55 of the 57 cases (96.5%). In four of the 55 cases, the decision based on ultrasound differed from the midwife's decision (7.3%). There was strong agreement between the decision to admit the pregnant women based on ultrasound measurements and the digital vaginal examination (Cohen's kappa: 0.844). It was possible to measure cervical dilation with ultrasound in 52 of the 57 cases (91.2%). The intraclass correlation coefficient for the cervical dilation measurements was 0.736 (95% confidence interval 0.539-0.848).

CONCLUSIONS

There was strong agreement between the ultrasound and digital vaginal examination results in the decision to admit singleton pregnant women at term due to labor. A large number of vaginal examinations could be avoided by using intrapartum ultrasound.

Quantitative assessment of cervical softening during pregnancy in the Rhesus macaque with shear wave elasticity imaging

Abnormal parturition, e.g. pre- or post-term birth, is associated with maternal and neonatal morbidity and increased economic burden. This could potentially be prevented by accurate detection of abnormal softening of the uterine cervix. Shear wave elasticity imaging (SWEI) techniques that quantify tissue softness, such as shear wave speed (SWS) measurement, are promising for evaluation of the cervix. Still, interpretation of results can be complicated by biological variability (i.e. spatial variations of cervix stiffness, parity), as well as by experimental factors (i.e. type of transducer, posture during scanning). Here we investigated the ability of SWEI to detect cervical softening, as well as sources of SWS variability that can affect this task, in the pregnant and nonpregnant Rhesus macaque. Specifically, we evaluated SWS differences when imaging the cervix transabdominally with a typical linear array abdominal transducer, and transrectally with a prototype intracavitary linear array transducer. Linear mixed effects (LME) models were used to model SWS as a function of menstrual cycle day (in nonpregnant animals) and gestational age (in pregnant animals). Other variables included parity, shear wave direction, and cervix side (anterior versus posterior). In the nonpregnant cervix, the LME model indicated that SWS increased by 2% (95% confidence interval 0-3%) per day, starting eight days before menstruation. During pregnancy, SWS significantly decreased at a rate of 6% (95% CI 5-7%) per week (intracavitary approach) and 3% (95% CI 2-4%) per week (transabdominal approach), and interactions between the scanning approach and other fixed effects were also significant. These results suggest that, while absolute SWS values are influenced by factors such as scanning approach and SWEI implementation, these sources of variability do not compromise the sensitivity of SWEI to cervical softening. Our results also highlight the importance of standardizing SWEI approaches to improve their accuracy for cervical assessment.

Detection of Changes in Cervical Softness Using Shear Wave Speed in Early versus Late Pregnancy: An in Vivo Cross-Sectional Study

The aim of this study was to assess the ability of shear wave elasticity imaging (SWEI) to detect changes in cervical softness between early and late pregnancy. Using a cross-sectional study design, shear wave speed (SWS) measurements were obtained from women in the first trimester (5-14 wk of gestation) and compared with estimates from a previous study of women at term (37-41 wk). Two sets of five SWS measurements were made using commercial SWEI applications on an ultrasound system equipped with a prototype catheter transducer (128 elements, 3-mm diameter, 14-mm aperture). Average SWS estimates were 4.42 ± 0.32 m/s (n = 12) for the first trimester and 2.13 ± 0.66 m/s (n = 18) for the third trimester (p <0.0001). The area under the curve was 0.95 (95% confidence interval: 0.82-0.99) with a sensitivity and specificity of 83%. SWS estimates indicated that the third-trimester cervix is significantly softer than the first-trimester cervix. SWEI methods may be promising for assessing changes in cervical softness.

Electrohysterography in the diagnosis of preterm birth: a review

Preterm birth (PTB) is one of the most common and serious complications in pregnancy. About 15 million preterm neonates are born every year, with ratios of 10-15% of total births. In industrialized countries, preterm delivery is responsible for 70% of mortality and 75% of morbidity in the neonatal period. Diagnostic means for its timely risk assessment are lacking and the underlying physiological mechanisms are unclear. Surface recording of the uterine myoelectrical activity (electrohysterogram, EHG) has emerged as a better uterine dynamics monitoring technique than traditional surface pressure recordings and provides information on the condition of uterine muscle in different obstetrical scenarios with emphasis on predicting preterm deliveries.

OBJECTIVE

A comprehensive review of the literature was performed on studies related to the use of the electrohysterogram in the PTB context.

APPROACH

This review presents and discusses the results according to the different types of parameter (temporal and spectral, non-linear and bivariate) used for EHG characterization.

MAIN RESULTS

Electrohysterogram analysis reveals that the uterine electrophysiological changes that precede spontaneous preterm labor are associated with contractions of more intensity, higher frequency content, faster and more organized propagated activity and stronger coupling of different uterine areas. Temporal, spectral, non-linear and bivariate EHG analyses therefore provide useful and complementary information. Classificatory techniques of different types and varying complexity have been developed to diagnose PTB. The information derived from these different types of EHG parameters, either individually or in combination, is able to provide more accurate predictions of PTB than current clinical methods. However, in order to extend EHG to clinical applications, the recording set-up should be simplified, be less intrusive and more robust-and signal analysis should be automated without requiring much supervision and yield physiologically interpretable results.

SIGNIFICANCE

This review provides a general background to PTB and describes how EHG can be used to better understand its underlying physiological mechanisms and improve its prediction. The findings will help future research workers to decide the most appropriate EHG features to be used in their analyses and facilitate future clinical EHG applications in order to improve PTB prediction.

New techniques in evaluation of the cervix

The process of parturition is poorly understood, but the cervix clearly plays a key role. Because of this, recent research efforts have been directed at objective quantification of cervical remodeling. Investigation has focused on two basic areas: (1) quantification of tissue deformability and (2) presence, orientation, and/or concentration of microstructural components (e.g. collagen). Methods to quantify tissue deformability include strain elastography and shear wave elasticity imaging (SWEI). Methods to describe tissue microstructure include attenuation and backscatter. A single parameter is unlikely to describe the complexities of cervical remodeling, but combining related parameters should improve accuracy of cervical evaluation. This chapter reviews options for cervical tissue characterization.