Monitoring the effacement of the uterine cervix by transperineal sonography: a new perspective

Transvaginal Ultrasound Findings Predicting Prolonged Pregnancy in Cases of Prolapsed Fetal Membrane: A Retrospective Study

Background/Objectives: Fetal membrane prolapse can occur due to advanced cervical insufficiency. We investigated the yet unclear predictors of prolonged pregnancy in women with prolapsed fetal membranes. Methods: This retrospective observational study included 100 pregnant women with prolapsed fetal membranes between November 2017 and March 2023. We examined the correlation between transvaginal ultrasound findings at the time of admission and the duration of prolonged pregnancy, which was defined as the period from admission to delivery. We defined five transvaginal ultrasound indices: (1) width of the external os, (2) maximum width of the prolapsed fetal membrane, (3) distance from the external os to the presenting part of the fetus, (4) thickness of the posterior uterine lip, and (5) morphology of the prolapsed fetal membrane. Results: Women who underwent cervical cerclage comprised the cerclage group (n = 17), while those who underwent conservative management comprised the non-cerclage group (n = 83). The pregnancy period was significantly longer in the cerclage group than in the non-cerclage group (81.4 days vs. 9.1 days, p < 0.001). Multiple regression analysis revealed that type A morphology was a significant factor for prolonged pregnancy in the non-cerclage group (p < 0.05), which was significantly associated with a prolonged pregnancy period of over 7 days (p = 0.037). Conclusions: In cases of prolapsed fetal membranes, cerclage is challenging because of the high risk of iatrogenic preterm rupture of the membrane; however, if successful, a significant prolongation of the pregnancy period can be obtained. Morphological evaluation using ultrasonography is simple and easy to understand and correlates well with pregnancy outcomes, making it very useful.

Unique risk factors for unplanned preterm delivery in the uterus transplant recipient

STUDY QUESTION

Do characteristics of the lower uterine segment and cervix modify the risk of preterm delivery in uterus transplant (UTx) recipients?

SUMMARY ANSWER

The cervical length showed little association with preterm delivery, however, cervical inflammation deserves further exploration as a cause of preterm delivery.

WHAT IS KNOWN ALREADY

UTx recipients do not have the risk factors normally used to stratify pregnancies that would benefit from cervical length assessment. In addition, unique factors related to absent tissues, a different blood supply, inflammatory processes of rejection, cervical biopsies, and a different microbiome challenge the normal progressive remodeling of the cervix and thus cervical competence.

STUDY DESIGN, SIZE, DURATION

This is a subanalysis of a clinical trial of 20 women undergoing uterus transplantation at Baylor University Medical Center from 2016 to 2020, in addition to two women who received transplantation outside of a research protocol at our institution through September 2022. In this report, the first 16 UTx recipients that achieved live birth are included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The focus of this study was 20 pregnancies that reached the second trimester in 16 women following UTx. We analyzed recipient, transplant, and donor factors to determine if characteristics were associated with delivery outcome. We compared obstetrical outcomes, including planned versus unplanned delivery, by factors such as number of superior venous anastomoses, warm ischemia and cold ischemia times, donor factors including cesarean sections, cervical biopsy results, and cervical ultrasound results.

MAIN RESULTS AND THE ROLE OF CHANCE

Planned term deliveries occurred in 44% (8/18) of live births. Of the preterm births, 30% (3/10) were planned and 70% (7/10) were unplanned. Unplanned deliveries occurred in women with spontaneous preterm labor, severe rejection, subchorionic hematoma, and placenta previa. Cervical length in UTx recipients averaged 33.5 mm at 24 weeks and 31.5 mm at 28 weeks, comparable to values from the general population. No relationship was seen between delivery outcome and number of veins used, ischemic time, or number of previous cesarean sections.

LIMITATIONS, REASONS FOR CAUTION

The study's small size allows limited conclusions. The obstetric history of all donors was limited to mode of delivery.

WIDER IMPLICATIONS OF THE FINDINGS

Cervical length measurements in the UTx population are not expected to deviate from those with a native uterus. While cervical length surveillance remains important, attention must be paid to the results of cervical biopsies which are obtained to monitor rejection. Inflammatory processes seem most predictive of preterm delivery.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was provided for this study. The authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

NCT02656550.

Proposed staging criteria for sonographic and physical exam for cervical changes at <24 weeks gestation to predict preterm birth

Asymptomatic cervical changes, such as cervical length shortening and dilation, which often occur before spontaneous preterm birth, have been described well in singleton pregnancies with or without history of preterm birth. The current screening strategies available to identify patients at increased risk of spontaneous preterm birth include use of transvaginal ultrasound for cervical length assessment and for detection of a short cervical length (≤25 mm) before 24 weeks of gestation. Whether an additional evaluation of the cervix (ie, via speculum or manual exam) is indicated is often pondered by clinicians and may depend on how short the cervical length is and if there is a history of preterm birth. Based on expert opinion, we developed a novel staging system of asymptomatic cervical changes including the following: cervical length measurement, cervical and membrane appearance on speculum exam, and cervical dilation by manual exam. This staging system, if proven accurate, may aid in standardizing definitions for purposes of patient prognosis, evaluation of intervention efficacy, and clinical management.

Bucket-handle cervical tear at term following oxytocin-induced vaginal delivery: a case report

BACKGROUND

A bucket-handle cervical tear, a laceration of the anterior or the posterior lip of the cervix so that it hangs like the handle of a bucket, is the rarest type of cervical laceration. Our case represents such a serious cervical laceration. A 28 year-old para 2 (both vaginal deliveries) Ethiopian mother presented at term with prolonged rupture of membrane. After 8 hours of oxytocin induction, a bucket-handle cervical detachment was detected at the time of her vaginal delivery, up on digital pelvic examination. Delivery of the baby was noted to be through the cervical tear, not the cervical opening. Cervix was amputated at the level of the cervical tear, 4 days after a failed initial repair surgery.

CONCLUSION

When bucket-handle cervical tear is encountered, a thorough clinical evaluation of the viability of the cervical tissue and feasibility of a repair procedure should be made during the first surgery. If the cervical detachment is near total, as in our case, we recommend amputation of the hanging cervical tissue from the outset.

Agreement between digital vaginal examination and intrapartum ultrasound for labour monitoring

Sonographic approach for labour monitoring was introduced in order to improve the shortcomings of digital vaginal examination (DVE). This was a prospective study. We aimed to investigate the agreement between transperineal ultrasound (TPUS) measurements and DVE during first and second stages of labour. Patients in the first stage of labour were included. Cervical length (CL), cervical dilation (CD), cervical position (CP), foetal head descent (FHD) and foetal head rotation (FHR) were assessed by both DVE and TPUS. Agreement between two methods was examined. Eighty-five patients were included. One hundred and eighty-three paired TPUS and DVE assessments were performed. Satisfactory agreement between both methods was obtained regarding CL: systematic bias= -0.05 cm (95%CI, -0.13; 0.03), R = 0.7, p<.0001; CD: systematic bias = 0.07 cm (95%CI, -0.08 to 0.22), R = 0.93, p<.0001 and FHD: systematic bias = 0.83 cm (95%CI, 0.685-0.977), R = 0.55, p<.0001. There was a low correlation for the assessment of CP (kappa = 0.24) and FHR (kappa = 0.06). DVE was inefficient in determining FHR especially during latent phase with failure and error rates of 86% and 36%, respectively. A conceptual sonopartogram covering the hole childbirth process is presented based on reliable ultrasound measurements.Impact StatementWhat is already known on this subject? Digital vaginal examination (DVE) is used worldwide for labour monitoring. However, it is far from perfect. Some investigators have raised concerns about the value of the Bishop score because it is a subjective measure with great intra- and inter-observer variability, affected by a physician's clinical experience. Moreover, this method is intrusive, uncomfortable and may increase the risk of infection. The sonographic approach for labour monitoring was introduced in order to improve the shortcomings of DVE. Multiple studies focussed on the reliability of the sonographic method in assessing each parameter during labour. Hassan et al. were the first to determine whether it is feasible to perform assessment in the first stage of labour based only on US, and to describe a method of recording these observations: the 'sonopartogram'.What do the results of this study add? The outcomes concluded that sonographic approach was at least as accurate as the clinical examination. Moreover, a conceptual sonopartogram covering the hole childbirth process is presented based on reliable ultrasound measurements.What are the implications of these findings for clinical practice and/or further research? Clinical relevance of this sonopartogram should be evaluated in further studies.

Transvaginal sonographic measurement of cervical length versus Bishop score in labor induction at term for prediction of caesarean delivery

OBJECTIVE

The current study aims to compare between a transvaginal sonographic measurement of cervical length and Bishop score in the induction of labor (IOL) at term for prediction of cesarean delivery (CD).

MATERIALS AND METHODS

A prospective cohort study included 320 full-term pregnant women attending Ain Shams Maternity Hospital in the period from August 2017 to February 2018 were enrolled. Seventy-three women were delivered by CD (positive group), and 247 women were delivered vaginally (negative group). All patients had a vaginal examination for assessing the Bishop Score before IOL then a transvaginal ultrasound for assessment of cervical length. IOL was initiated by using PGE1 analog. The primary outcome measure was the accuracy of the cervical length or the bishop score for prediction of the CD.

RESULTS

In our current study, CD was achieved in 22.8% of all participants while vaginal delivery was achieved in 77.8% after IOL by misoprostol 25 micrograms within 24 h from the beginning of induction. Both the cervical length and Bishop Score had poor predictive value for CD (AUC = 0.694 and 0.623, respectively).

CONCLUSIONS

Both transvaginal sonography for cervical length and Bishop score are useful predictors of the need for CD following labor induction.

Guideline No. 401: Sonographic Cervical Length in Singleton Pregnancies: Techniques and Clinical Applications

OBJECTIVES

• To assess the association between sonography-derived cervical length measurement and preterm birth. • To describe the various techniques to measure cervical length using sonography. • To review the natural history of the short cervix. • To review the clinical uses, predictive ability, and utility of sonography-measured short cervix.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

INTENDED USERS

Clinicians involved in the obstetrical management or cervical imaging of patients at increased risk of a short cervix.

TARGET POPULATION

Women at increased risk of a short cervix or at risk of preterm birth.

EVIDENCE

Literature published up to June 2019 was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, cervical insufficiency, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made and graded according to the rankings of the Canadian Task Force on Preventive Health Care (Online Appendix Table A1).

BENEFITS, HARMS, COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the sonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth. SUMMARY STATEMENTS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES): RECOMMENDATIONS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES).

The impact of funneling shape on the secondary prevention of spontaneous preterm birth in patients treated with either an Arabin pessary, McDonald cerclage or early total cervical occlusion (ETCO)

OBJECTIVE

Cervical funneling is associated with spontaneous preterm birth (sPTB). The aim of this analysis was to assess the relationship between funneling shape and the response to the McDonald cerclage, the Arabin pessary and the early total cervical occlusion (ETCO).

METHODS

We retrospectively analyzed data of 312 randomly selected singleton pregnancies with cervical shortening <25 mm or normal cervical length and evaluated them according to the progression of funneling: control group (n = 46), cervical shortening without funneling (n = 107), V-shaped funneling (n = 68), U-shaped funneling (n = 47), and prolapse of the amniotic sac (n = 44). We evaluated sPTB rates <34, <28, <32, and <37 weeks as well as prolongation of gestation and birthweight.

RESULTS

Regarding the rate of sPTB <34 weeks there was no statistical significance in either of the comparisons between control group and each of the four risk groups. Regarding prolongation of gestation we demonstrated a statistical significance for all risk groups compared to the control group (all p < .05) with the lowest prolongation rate noted in the group with amnion prolapse and the highest in the group with isolated cervical shortening without funneling. Similarly, progression of funnel shape resulted in an absolute decrease of birthweight for all risk groups compared to the control group, albeit not significant for the group with U-shaped funneling (p = .1058).

CONCLUSION

Independent of the treatment, there was a significant impact of funneling shape on pregnancy duration and birthweight.

Prediction of preterm birth: the role cervical assessment by ultrasound and cervico-vaginal biomarkers

Preterm delivery (PTB) is one of the most common and serious complications of pregnancy. PTB accounts for approximately 70% of neonatal deaths and is a major cause of neonatal morbidity including respiratory distress syndrome, necrotising enterocolitis and long-term neurological disabilities. Prevention of PTB and its complications include identification among symptomatic women those at high risk of immediate delivery requiring prenatal corticosteroids administration. Transvaginal ultrasonographic evaluation of the cervical length (CL) is predictive of PTB and a value 15 mm identifies among symptomatic women approximately 70% of women who will deliver within one week. In the range of CL within 15 and 30 mm biomarkers n cervical-vaginal fluids (fetal fibronectin, phosphorylated insulin-like growth factor protein-1, placental alpha-microglobulin-, cytokines) and other ultrasonographic cervical variables (posterior cervical angle, elastography) improve the identification of women at risk, In asymptomatic women CL can be applied as screening and has been proposed as a universal screening during the second trimester in singleton gestations. The finding of a CL25mm is associated with an increased risk of subsequent PTB with a sensitivity between 30 and 60% that is improved with the combination of biomarkers. Asymptomatic women with a CL 25mm should be offered vaginal progesterone treatment for the prevention of preterm birth and neonatal morbidity. The role of cerclage and pessary is still controversial. In this review we discuss the evidence-based role of ultrasonographic cervical assessment and cervicovaginal biomarkers in the prediction of PTB in symptomatic and asymptomatic women

Uterocervical angle measurement for preterm birth prediction in singleton pregnant women with no history of preterm birth and normal cervical length: A prospective cohort study

OBJECTIVE

To evaluate the ability of second trimester uterocervical angle (UCA) to predict spontaneous preterm birth (sPTB) in low-risk singleton pregnant women.

STUDY DESIGN

Transvaginal sonographies were performed in the second trimester of 450 singleton pregnant women with no history of sPTB and no history of second trimester miscarriage with normal cervical length (CL) who attended antenatal care at Songklanagarind Hospital, a tertiary teaching hospital in southern Thailand. Gestational ages at delivery were recorded then the UCA values were evaluated according to sPTB occurrence. The differences in mean values of UCA between sPTB and full-term groups were evaluated using t-test. A receiver operating characteristics (ROC) curve was used to assess the ability of UCA to predict sPTB.

RESULTS

After excluding women with unknown pregnancy outcomes or missing UCA images, the sPTB rate was 34/421 (8.1 %). In women with anteflexed uterus, the mean UCA value was wider in the sPTB group compared to those with term birth if the measurements were performed at GA 19.5-24 weeks (sPTB group, 123.4°vs controls, 104.3°; P = 0.017). The ROC curve showed an area under the curve (AUC) of 0.7045. The optimal UCA cut-off value was ≥110 degrees, which gave a sensitivity of 83.3 % and a specificity of 61.2 %. The positive predictive value (PPV) was 16.7 %, negative predictive value (NPV) 97.5 %, positive likelihood ratio (LR+) 2.2 and negative likelihood ratio (LR-) 0.3.

CONCLUSION

The UCA in the second trimester is not a good predictor of sPTB in low risk pregnant women.

Distribution of uterocervical angles in the second trimester of pregnant women at low risk for preterm delivery

The uterocervical angle (UCA) has recently been studied as a parameter to identify women at risk for spontaneous preterm birth (sPTB). This study aimed to investigate the distribution of UCA values by transvaginal sonography (TVS) in the second trimester of women at low risk for sPTB. TVS was performed in 450 low-risk pregnant women at gestational age (GA) 16^0/7-24^0/7weeks. The UCA distribution by GA was visualised using a scatter plot. The range of UCA values and their relationship with GA were assessed using quantile regression analysis. p < .05 was considered statistically significant. A total of 242 participants with anteflexed uterus, no history of caesarean section and term delivery were analysed. The normal range of UCA (5th and 95th percentiles) was from 63.0 degrees (95% CI, 53.1-72.9) to 148.8 degrees (95% CI, 139.5-158.0) with no significant changes during this GA period (-0.3 degrees per week, p = .757).Impact statementWhat is already known on this subject? Spontaneous preterm birth (sPTB) is a major problem in obstetrics. A screening strategy using history of sPTB and cervical length (CL) measurement is the current standard to identify women at risk for sPTB and provide adequate prevention. However, a third of women who are identified as low risk go on to have sPTB, so a better means needs to be found to more reliably identify women at risk. Various studies have found that a wide uterocervical angle (UCA) was associated with sPTB, and thus the UCA has been proposed as a potential sPTB screening parameter. However, to date there is a lack of prospective studies evaluating this proposal, and no consensus about the proper gestational age to perform UCA measurements to identify women at risk of sPTB.What do the results of this study add? This study reports the distribution of UCA at the GA of 16^0/7-24^0/7 weeks of low-risk singleton pregnancy women who delivered at term. The mid-90% values ranged from 63.0 degrees to 148.8 degrees with no significant differences in this GA period.What are the implications of these findings for clinical practice and/or further research? Because of the wide range of UCA values at GA 16^0/7-24^0/7 weeks, more studies regarding UCA values in various gestational ages are required to fully understand the trend of UCA values along pregnancy and confirm whether or not the UCA would be a useful parameter for sPTB prediction and if so at what gestational age it would have to be assessed.

Quantitative Ultrasound Detects Smooth Muscle Activity at the Cervical Internal Os in Vitro

The cervix has two biomechanical functions: to remain closed while the fetus develops throughout pregnancy, and to open for delivery of the fetus at full term. This dual function is principally attributed to collagen within the extracellular matrix (ECM). However, recent evidence suggests that other ECM, and non-ECM, components play a role as well. One component is smooth muscle cells arranged circumferentially near the internal os. In this study, we investigate correlations between cervical smooth muscle cell force generation and the effective scatterer diameter (ESD), a quantitative ultrasound parameter directly related to the acoustic impedance distribution and, therefore, a potential biomarker of muscle contractility. Using whole cervical slices (N = 5), we determined significant positive correlations (quantified with Pearson's r) between muscle force generation and ESD immediately after administration of oxytocin (median r = 0.90). In summary, the ESD may prove a useful biomarker for studying structure and function of cervical smooth muscle in vivo.

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.

Cervical Funneling: Potential Pitfall of Point-of-Care Pelvic Ultrasound

Though point-of-care ultrasound applications continue to expand, there are findings that are not within the scope of emergency ultrasound. It is important for emergency physicians to be aware of incidental findings that can be identified on comprehensive ultrasounds performed by other imaging departments in order to fully understand the limitations of bedside ultrasound. In this case, a gravid patient presented to the emergency department with pelvic cramping and vaginal bleeding. Point-of-care transabdominal pelvic ultrasound examination was performed and demonstrated cervical funneling. In the appropriate patient, cervical insufficiency due to cervical funneling may be an indication for cerclage in a pregnant patient.

Cervical Evaluation in Pregnancy: Proper Measurement, Evaluation, and Management

Preterm birth is the leading cause of perinatal morbidity and mortality in developed nations. The heterogeneous causes of spontaneous preterm birth make prediction and prevention difficult. The primary importance of transvaginal cervical sonography and cervicovaginal fetal fibronectin lies in their high negative predictive values in assessing risk for preterm birth. Cervical length may be useful in identifying women who are candidates for cervical cerclage or progesterone therapy for preterm birth prevention. Together, cervical length and fibronectin can be used in the triaging of women symptomatic for preterm labor.

Vaginal Cerclage: Preoperative, Intraoperative, and Postoperative Management

The role of the cerclage procedure has expanded from its initial application as treatment or prevention of cervical insufficiency to prevention of recurrent spontaneous preterm birth. Although recent prospective studies have clarified the indications for cerclage, additional prospective studies are needed to help define optimal perioperative management. Herein, we review the current data to provide the clinician with the most evidence-based approach to managing patients who require cerclage.

Magnetic Resonance Signal Characteristics of the Cervix as Pregnancy Advances

The objective of this study is to describe magnetic resonance (MR) signal intensity (SI) changes in the cervix during pregnancy. This is an observational cohort study of women with a history of preterm delivery. MR imaging sequences were performed every 3 to 4 weeks. Using 8 regions of interest, the SIs are quantified and analyzed with respect to gestational age. Twenty-seven MR studies were performed on a cohort of 8 women. The SIs of the external os are significantly greater than those of the internal os ( P = .035). Similarly, the SIs of the outer stroma are greater than those of the inner stroma (P = .002). As gestational age advances, the inner to outer stromal SI ratio increases, primarily because of a decreasing SI in the outer stromal layer (P = .03). The MR SIs of the cervical stromal zones display variability during pregnancy and decrease with advancing gestation.

The mechanical role of the cervix in pregnancy

Appropriate mechanical function of the uterine cervix is critical for maintaining a pregnancy to term so that the fetus can develop fully. At the end of pregnancy, however, the cervix must allow delivery, which requires it to markedly soften, shorten and dilate. There are multiple pathways to spontaneous preterm birth, the leading global cause of death in children less than 5 years old, but all culminate in premature cervical change, because that is the last step in the final common pathway to delivery. The mechanisms underlying premature cervical change in pregnancy are poorly understood, and therefore current clinical protocols to assess preterm birth risk are limited to surrogate markers of mechanical function, such as sonographically measured cervical length. This is what motivates us to study the cervix, for which we propose investigating clinical cervical function in parallel with a quantitative engineering evaluation of its structural function. We aspire to develop a common translational language, as well as generate a rigorous integrated clinical-engineering framework for assessing cervical mechanical function at the cellular to organ level. In this review, we embark on that challenge by describing the current landscape of clinical, biochemical, and engineering concepts associated with the mechanical function of the cervix during pregnancy. Our goal is to use this common platform to inspire novel approaches to delineate normal and abnormal cervical function in pregnancy.

Investigating the mechanical function of the cervix during pregnancy using finite element models derived from high-resolution 3D MRI

Preterm birth is a strong contributor to perinatal mortality, and preterm infants that survive are at risk for long-term morbidities. During most of pregnancy, appropriate mechanical function of the cervix is required to maintain the developing fetus in utero. Premature cervical softening and subsequent cervical shortening are hypothesized to cause preterm birth. Presently, there is a lack of understanding of the structural and material factors that influence the mechanical function of the cervix during pregnancy. In this study we build finite element models of the pregnant uterus, cervix, and fetal membrane based on magnetic resonance imagining data in order to examine the mechanical function of the cervix under the physiologic loading conditions of pregnancy. We calculate the mechanical loading state of the cervix for two pregnant patients: 22 weeks gestational age with a normal cervical length and 28 weeks with a short cervix. We investigate the influence of (1) anatomical geometry, (2) cervical material properties, and (3) fetal membrane material properties, including its adhesion properties, on the mechanical loading state of the cervix under physiologically relevant intrauterine pressures. Our study demonstrates that membrane-uterus interaction, cervical material modeling, and membrane mechanical properties are factors that must be deliberately and carefully handled in order to construct a high quality mechanical simulation of pregnancy.

A systematic evaluation of collagen cross-links in the human cervix

OBJECTIVE

The mechanical strength of the cervix relies on the cross-linking of the tissue's collagen network. Clinically, the internal os is functionally distinct from the external os. We sought to detect specific collagen cross-links in human cervical tissue and determine whether cross-link profiles were similar at the internal and external os.

STUDY DESIGN

Transverse slices of cervical tissue were obtained at the internal and external os from 13 nonpregnant, premenopausal women undergoing a benign hysterectomy. To understand how cross-links were distributed throughout the entire cervix and at the internal and external os, biopsies were obtained from 3 circumferential zones in 4 quadrants from each slice. Biopsies were pulverized, lyophilized, reduced with sodium borohydride, hydrolyzed with hydrochloric acid, and reconstituted in heptafluorobutyric acid buffer. Hydroxyproline was measured by ultraperformance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS), converted to total collagen, and normalized by dry weight. Collagen cross-links pyridinoline (PYD), deoxypyridinoline (DPD), dihydroxylysinonorleucine (DHLNL), and the nonenzymatic advanced glycation end product pentosidine (PEN) were measured by UPLC-ESI-MS/MS and reported as cross-link density ratio (cross-link/total collagen). Generalized estimated equation analysis was used to compare results between the internal and external os and to compare quadrants and zones within slices from the internal and external os to determine if cross-link profiles were similar.

RESULTS

A total of 592 samples from 13 patients were analyzed. Collagen cross-links are detectable in the human cervix by UPLC-ESI-MS/MS. When comparing all samples from the internal and external os, similar levels of collagen content, PYD, DHLNL, and DPD were found, but PEN density was higher at the external os (0.005 vs 0.004, P = .001). When comparing all internal os samples, significant heterogeneity was found in collagen content and cross-link densities across zones and quadrants. The external os exhibited heterogeneity only across zones.

CONCLUSION

Collagen cross-links (PYD, DPD, DHLNL, and PEN) are detectable by UPLC-ESI-MS/MS in the human cervix. The internal os exhibits significant collagen cross-link heterogeneity compared with the external os. Further studies are needed to evaluate how collagen cross-link heterogeneity correlates to the mechanical strength and function of the human cervix.

Spontaneous delivery through a cervical tear without cervical os dilatation

Spontaneous delivery through a cervical tear, provoked by prostaglandin-induced uterine contractions, was described in a G2P0 woman with a history of cervical dilatation and uterine curettage. This rare complication with potentially serious maternal–fetal consequences can be predicted by an aberrant cervical response to prostaglandins in parturients with previous cervical interventions.

Precocious cervical ripening as a screening target to predict spontaneous preterm delivery among asymptomatic singleton pregnancies: a systematic review

Routine second-trimester transvaginal ultrasonographic (TVU) screening for short cervical length (CL) predicts spontaneous preterm delivery (SPTD), albeit with limited sensitivity (35-40%) and a moderate positive likelihood ratio of 4-6. However, CL describes one of the multidimensional changes that are associated with precocious cervical ripening (PCCR) and that also include cervical softening, cervical funneling (CF), and dilation. PCCR, a precursor and a strong predictor for SPTD, was proposed as a potential screening target. We hypothesized that screening for composite measures of PCCR (eg, CL, CF, cervical consistency, and dilation) with the use of either digital examination or TVU would improve the prediction of SPTD compared with screening for short CL alone. We searched PubMed and EMBASE electronic databases for observational cohort studies to evaluate cervical screening in asymptomatic obstetric populations. Multidimensional composite cervical measures were assessed in 10 datasets (n = 22,050 pregnancies) and 12 publications. Appreciable heterogeneity in cervical measurements, data quality, and outcomes across studies prevented quantitative metaanalysis. Only one study reported intra- and interobserver reliability of cervical measurements. The prevalence of CF ranged from 0.7-9.1%. Five studies compared composite measures of PCCR (ie, CL and CF) with short CL alone and consistently reported improved screening performance. Among 3 TVU studies, gains in sensitivity ranged from 5-27%, and increases in positive likelihood ratio ranged from 3-16. Our findings suggest that composite measures of PCCR might serve as valuable screening targets. High-quality interdisciplinary studies that integrate epidemiologic approaches are needed to test this hypothesis and to accelerate the translation of advances in cervical pathophysiology into effective preventive interventions.

Prominent cervical mucous and its impact on cervical length measurement: findings of a national survey

INTRODUCTION

Cervical length measurement by transvaginal scanning (TVS) has been proposed by some as a universal screening test for preterm labour. The presence of prominent cervical mucous may affect assessment of the cervix; however, the exact technique to measure the cervix when there is prominent mucous or funnelling has not been described. We evaluated the level of agreement in cervical length measurements amongst Australian specialists and sonographers reporting on cervical assessment using an online survey.

METHODS

We conducted an online survey with 11 images of the cervix to assess how obstetric sonographers and sonologists report on the cervix when there is prominent mucous or funnelling. They were asked five questions about the image of the cervix. A kappa coefficient was calculated from the responses.

RESULTS

We had 151 complete responses to the online survey. For the images which showed funnelling or prominent cervical mucous, there was little agreement regarding the cervix being open or closed and regards the location of the internal os. The Kappa coefficient was 0.22 indicating a low level of agreement for the location of the internal os.

CONCLUSION

There is lack of agreement amongst Australian specialists and sonographers reporting on cervical assessment when there is prominent mucous or funnelling seen in the cervix. We propose a method to standardise reporting on the cervix incorporating the chorioamniotic membrane for the identification of the inner cervical os when there is prominent mucous or funnelling.

Prevention of periviable birth: bed rest, tocolysis, progesterone, and cerclage

The periviable period is associated with a rapid improvement in both mortality and morbidity with increasing gestational age. Therapies that can prolong gestation have the potential for markedly improving outcome compared to later in pregnancy. The therapies commonly prescribed in order to prolong gestation include bed rest, tocolysis, progesterone, and cerclage. Although these therapies are used to prevent preterm birth throughout gestation, their impact on perinatal outcome during the periviable period remains largely unknown. These therapies are discussed relative to the periviable period exploring available data and possible impact on perinatal outcome. Studies specifically evaluating therapeutic interventions during the periviable period are lacking.

Simple two-dimensional ultrasound technique to assess intrapartum cervical dilatation: a pilot study

OBJECTIVES

To describe a two-dimensional (2D) ultrasound technique to measure cervical dilatation in labor, and to compare ultrasound with digital measurements.

METHODS

2D transperineal ultrasound was performed in 21 nulliparous women in labor with a singleton fetus in cephalic presentation and cervical dilatation measured before or after a digital vaginal examination. The absolute difference was calculated and Bland-Altman analysis was used to assess the mean difference between digital vaginal examination and ultrasound examination of cervical dilatation. Pearson analysis was used to determine the correlation between digital and ultrasound measurements. Intraclass correlation coefficients (ICCs) with 95% CI were used to evaluate the reliability of the two methods.

RESULTS

Satisfactory quality images of the cervix were obtained in 19 of 21 cases. There was positive correlation between 2D ultrasound measurement of cervical dilatation and digital vaginal examination (Pearson coefficient r = 0.821, n = 19, P < 0.001). Bland-Altman analysis showed a mean difference between digital and ultrasound measurements of 0.08 cm (95% limits of agreement: -1.83 to 2.00) and the mean absolute difference was 1.24 cm. The ICC between the two methods was 0.81 (95% CI, 0.58-0.92).

CONCLUSIONS

Assessment and measurement of cervical dilatation by 2D transperineal ultrasound is feasible, with close agreement shown between the technique and digital vaginal examination. The technique that we describe could represent an important component of a 'sonopartogram' for ultrasound assessment of labor progress.

System-level biomechanical approach for the evaluation of term and preterm pregnancy maintenance

Preterm birth is the primary contributor to perinatal morbidity and mortality, with those born prior to 32 weeks disproportionately contributing compared to those born at 32-37 weeks. Outcomes for babies born prematurely can be devastating. Parturition is recognized as a mechanical process that involves the two processes that are required to initiate labor: rhythmic myometrial contractions and cervical remodeling with subsequent dilation. Studies of parturition tend to separate these two processes rather than evaluate them as a unified system. The mechanical property characterization of the cervix has been primarily performed on isolated cervical tissue, with an implied understanding of the contribution from the uterine corpus. Few studies have evaluated the function of the uterine corpus in the absence of myometrial contractions or in relationship to retaining the fetus. Therefore, the cervical-uterine interaction has largely been neglected in the literature. We suggest that a system-level biomechanical approach is needed to understand pregnancy maintenance. To that end, this paper has two main goals. One goal is to highlight the gaps in current knowledge that need to be addressed in order to develop any comprehensive and clinically relevant models of the system. The second goal is to illustrate the utility of finite element models in understanding pregnancy maintenance of the cervical-uterine system. The paper targets an audience that includes the reproductive biologist/clinician and the engineer/physical scientist interested in biomechanics and the system level behavior of tissues.

Using imaging-based, three-dimensional models of the cervix and uterus for studies of cervical changes during pregnancy

Preterm birth affects over 12% of all pregnancies in the United States for an annual healthcare cost of $26 billion. Preterm birth is a multifactorial disorder but cervical abnormalities are a prominent feature in many patients. Women with a short cervix are known to be at increased risk for preterm birth and a short cervix is used to target therapy to prevent preterm birth. Although the clinical significance of a short cervix is well known, the three-dimensional anatomical changes that lead to cervical shortening are poorly understood. Here, we review our previous studies of the three-dimensional anatomy of the cervix and uterus during pregnancy. The rationale for these studies was to improve our understanding of the deformation mechanisms leading to cervical shortening. Both magnetic resonance imaging and three-dimensional (3D) ultrasound were used to obtain anatomical data in healthy, pregnant volunteers. Solid models were constructed from the 3D imaging data. These solid models were used to create numerical models suitable for biomechanical simulation. Three simulations were studied: cervical funneling, uterine growth, and fundal pressure. These simulations showed that cervical changes are a complex function of the tissue properties of the cervical stroma, the loading conditions associated with pregnancy and the 3D anatomical geometry of the cervix and surrounding structures. An improved understanding of these cervical changes could point to new approaches to prevent undesired cervical shortening. This new insight should lead to therapeutic strategies to delay or prevent preterm birth.

Is sonographic assessment of the cervix necessary and helpful?

Transvaginal sonography of the cervix has emerged as a useful window into preterm parturition. Cervical sonography allows measurements of cervical length (CL), which can aid clinicians in identifying women at risk for preterm birth. The use of transvaginal assessments of CL can assist in the triage of patients with possible preterm labor. Recent studies also support the use of CL measurements as a means of determining appropriate candidates for cerclage placement and progesterone supplementation to reduce the risk of premature birth, further highlighting the importance of this modality in modern obstetric management.

Compression-dependent viscoelastic behavior of human cervix tissue

We have characterized the viscoelastic properties of human cervical tissue through a range of precompressional loads and testing frequencies. Mechanical testing is necessary to develop robust elasticity-based techniques for the diagnosis of cervical abnormalities. The storage modulus (E') and material damping (tan 6) were measured in 13 patients, 40 to 76 years old. Our results showed that E' increased monotonically from approximately 4.7 to 6.3 kPa over the precompression range (1-6%) for a testing frequency of 1 Hz. Increases in precompressions of 4% or greater significantly increased E' obtained after dynamic compression testing when data were normalized to 1% precompression. Tan delta remained fairly constant (approximately 0.35) and was not significantly affected by changes in precompression. E' and tan delta increased significantly with frequency. E 'monotonically increased from 4.7 to 7.9 kPa for the 1-3% compression range (lowest precompression for 2% amplitude) and from 6.3 to 10.3 kPa for the 6-8% range (highest precompression for 2% amplitude) when increasing frequency from 1 to 30 Hz. Tan delta increased montonically from 0.35 to 0.45 for 2% amplitude compressions from 1 to 30 Hz regardless of initial precompression. Our results show that precompression and testing frequency must be taken into account in order to obtain consistent measurements in mechanical diagnostic tests developed for cervical abnormalities.

Cervical funneling: effect on gestational length and ultrasound-indicated cerclage in high-risk women

OBJECTIVE

The purpose of this study was to assess funnel type and pregnancy duration in women with previous spontaneous preterm birth and cervical length <25 mm.

STUDY DESIGN

We performed a secondary analysis of a multicenter randomized trial of cerclage. At the randomization scan that documented short cervix, the presence and type of funnel (U or V) were recorded.

RESULTS

One hundred forty-seven of 301 women (49%) had funneling: V-shaped funnel, 99 women; U-shaped funnel, 48 women. U-shaped funnel was associated significantly with preterm birth at <24, <28, <35, and <37 weeks of gestation. In multivariable models that controlled for randomization cervical length and cerclage, women with U-shaped funnel delivered earlier than women with either V-shaped funnel or no funnel. Interaction between cerclage and U-shaped funnel was observed, and analyses that were stratified by cerclage showed that women with a U-shaped funnel and cerclage delivered at a mean of 33.8 +/- 6.6 weeks of gestation, compared with women who did not receive cerclage (28.9 +/- 6.9 weeks of gestation).

CONCLUSION

U-shaped funnels in high-risk women with a short cervix are associated with earlier birth.

Intrapartum measurement of cervical dilatation using translabial 3-dimensional ultrasonography: correlation with digital examination and interobserver and intraobserver agreement assessment

OBJECTIVE

The purpose of this study was to determine the accuracy and reproducibility of intrapartum translabial 3-dimensional (3D) ultrasonographic measurements of cervical dilatation during labor.

METHODS

A prospective observational study was conducted. Three-dimensional ultrasonographic volume data sets from 52 patients were collected during labor and stored. Later, all volumes were randomly reviewed twice offline by 2 examiners blinded to previous clinical and ultrasonographic measurements. The correlation with delivery room personnel digital vaginal examinations and interobserver and intraobserver agreement were determined.

RESULTS

Twenty-four patients were examined during the latent phase (0- to 4-cm cervical dilatation), and 28 patients were examined during the active phase (5- to 10-cm cervical dilatation). Translabial 3D ultrasonographic measurements of the cervical mean and maximal diameters and inner cervical area showed a positive correlation with digital vaginal examinations (r(2) = 0.609, 0.587, and 0.469, respectively; all P < .001). The interobserver mean differences +/- SD between paired measurements for the mean and maximal cervical dilatation and inner cervical area were 0.11 +/- 0.49 cm, 0.12 +/- 0.48 cm, and -0.22 +/- 5.69 cm(2), and the intraclass correlation coefficients (ICCs) were 0.82, 0.85, and 0.87. The intraobserver mean differences between paired measurements of the mean and maximal cervical dilatation and inner cervical area were 0.002 +/- 1.15 cm, 0.02 +/- 1.4 cm, and -0.41 +/- 1.15 cm(2), and the ICCs were 0.85, 0.79, and 0.75.

CONCLUSIONS

Assessment of cervical dilatation using 3D ultrasonography during labor is feasible and reproducible.

Methods of sonographic cervical length measurement in pregnancy: A review of the literature

In this review we give an overview of the methods and pitfalls in cervical length measurements. We compared the different techniques and investigated factors that influence visualization of the cervix. The data in this overview may be used to establish guidelines in clinical practice.

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.

Transvaginal ultrasonographic cervical measurement in predicting failed labor induction and cesarean delivery for failure to progress in nulliparous women

The aim of this study was to evaluate the value of transvaginal sonographic cervical measurement in predicting failed labor induction and cesarean delivery for failure to progress in nulliparous women. One hundred and sixty-one women scheduled for labor induction underwent transvaginal ultrasonography and digital cervical examinations. Logistic regression demonstrated that cervical length and gestational age at induction, but not the Bishop score, significantly and independently predicted failed labor induction. According to the receiver operating characteristic curves analysis, the best cut-off value of cervical length for predicting failed labor induction was 28 mm, with a sensitivity of 62% and a specificity of 60%. In terms of the likelihood of a cesarean delivery for failure to progress as the outcome variable, logistic regression indicated that maternal height and birth weight, but not cervical length or Bishop score, were significantly and independently associated with an increased risk of cesarean delivery for failure to progress. Transvaginal sonographic measurements of cervical length thus independently predicted failed labor induction in nulliparous women. However, the relatively poor predictive performance of this test undermines its clinical usefulness as a predictor of failed labor induction. Moreover, cervical length appears to have a poor predictive value for the likelihood of a cesarean delivery for failure to progress.

Progressive cervical length changes versus single cervical length measurement by transvaginal ultrasound for prediction of preterm delivery

BACKGROUND

To evaluate cervical length changes as predictors of preterm delivery.

METHODS

Two hundred and fifty-seven pregnant women underwent transvaginal ultrasound examination at 16 and 24 weeks of gestation. Cervical length was measured and the difference between the 2 measurements was calculated. The sensitivity, specificity, positive predictive value and negative predictive value of cervical length and cervical length changes were calculated and these methods were compared by receiver-operating characteristic (ROC) curve analysis.

RESULTS

Preterm delivery (before 37 weeks of gestation) occurred in 19 patients (7.4%). The mean cervical length was shorter in the preterm group, the area under the ROC curve for prediction of preterm delivery was 0.914, ultrasound had a sensitivity of 84.2% to predict preterm delivery with a false-positive rate of 18.5%, and the relative risk was 4.56 at the 34.3-mm cutoff value at 24 weeks of gestation. In contrast, a cervical length change on transvaginal ultrasound had a sensitivity of 73.3% to predict preterm delivery with a false-positive rate of 18.1%, and the relative risk was 4.08 at the 6.6-mm cutoff value.

CONCLUSION

A single cervical length measurement obtained at 24 weeks of gestation can predict preterm delivery as accurately as cervical length change.

Natural History of Cervical Funneling in Women at High Risk for Spontaneous Preterm Birth

OBJECTIVE

To estimate the natural history of funneling in the second trimester by transvaginal ultrasonograms and whether funneling increases the risk of spontaneous birth.

METHODS

Secondary analysis of a blinded, multi-center observational study of women with at least one prior spontaneous preterm birth at 16.0-31.9 weeks who subsequently carried singleton gestations. Cervical length, funneling (membrane prolapse greater than or equal to 5 mm), funnel shape, and dynamic changes were recorded at 16-18 weeks, and then every 2 weeks until 23.9 weeks. Managing obstetricians were blinded to the ultrasonography results. The primary outcome was gestational age at delivery.

RESULTS

Five hundred ninety scans were performed in 183 women, of which 60 (33%) had funneling observed on at least one of the serial evaluations. These 60 women delivered at an earlier gestational age at delivery than the 123 women without funneling (31.7+/-7.9 weeks compared with 36.9+/-4.4 weeks; P<.001). In the 60 women with funneling on at least one evaluation, the progression over time of internal os cervical anatomy from a "T" to a "V" to a "U" shape was associated with earlier gestational age at delivery, whereas resolution of "V" shape funnels was associated with term delivery. Women with a shortened cervical length less than 25 mm (n=60) had a similar gestational age at birth with or without funneling (30.6+/-8.0 weeks compared with 31.9+/-6.6 weeks; P=.59). After controlling for the shortest observed cervical length, largest funnel percent was not a significant independent risk factor.

CONCLUSION

The natural history of second-trimester funneling has significant variability and a significant association with earlier gestational age at delivery. As an independent finding, funneling does not add appreciably to the risk of early gestational age at delivery associated with a shortened cervical length.

LEVEL OF EVIDENCE

II.

In vivo characterization of the mechanics of human uterine cervices

The uterine cervix has to provide mechanical resistance to ensure a normal development of the fetus. This is guaranteed by the composition of its extracellular matrix, which functions as a fiber-reinforced composite. At term a complex remodeling process allows the cervical canal to open for birth. This remodeling is achieved by changes in the quality and quantity of collagen fibers and ground substance and their interplay, which influences the biomechanical behavior of the cervix but also contributes to pathologic conditions such as cervical incompetence (CI). We start by reviewing the anatomy and histological composition of the human cervix, and discuss its physiologic function and pathologic condition in pregnancy including biomechanical aspects. Established diagnostic methods on the cervix (palpation, endovaginal ultrasound) used in clinics as well as methods for assessment of cervical consistency (light-induced fluorescence, electrical current, and impedance) are discussed. We show the first clinical application of an aspiration device, which allows in vivo testing of the biomechanical properties of the cervix with the aim to establish the physiological biomechanical changes throughout gestation and to detect pregnant women at risk for CI. In a pilot study on nonpregnant cervices before and after hysterectomy we found no considerable difference in the biomechanical response between in vivo and ex vivo. An outlook on further clinical applications during pregnancy is presented.

Prediction of labor and delivery by transperineal ultrasound in pregnancies with prelabor rupture of membranes at term

OBJECTIVE

To evaluate whether engagement of the fetal head or cervical length in women with premature rupture of membranes (PROM) at term, are associated with time from PROM to delivery or need for operative delivery.

METHODS

A transperineal ultrasound examination was performed in 152 women with a single live fetus in cephalic presentation after PROM (at > 37 gestational weeks). The shortest distance from the outer bony limit of the fetal skull to the skin surface of the perineum was measured in a transverse view, and the cervical length was measured in a sagittal view. The time from PROM to delivery was tested in a Cox regression analysis with ultrasound measurements, parity, maternal age, body mass index and birth weight as possible predictive factors.

RESULTS

The head-perineal distance was associated with the time from PROM to delivery (log rank test, P < 0.001). Thirty-six hours after PROM, 32% (95% CI, 15-49) of women with a short head-perineal distance (< 45 mm) and 43% (95% CI, 24-62) of women with a long distance (> or = 45 mm) were still in labor. Women with a short head-perineal distance had fewer Cesarean sections, less use of epidural analgesia and a shorter time in active labor, and their babies had a higher pH in the umbilical artery. The measured cervical length was not associated independently with time to delivery.

CONCLUSION

Transperineal ultrasound measurements of fetal head engagement may help clinicians to predict the course of labor in women with PROM.