Cervical assessment at the routine 23-weeks' scan: problems with transabdominal sonography

Cervical assessment certification and its impact on performance quality in the context of universal cervical screening

OBJECTIVE

To assess the impact of the introduction of universal transvaginal cervical screening and certification on the quality of cervical length ultrasound images.

METHODS

The present study included a retrospective cohort of singleton pregnancies that underwent transvaginal cervical length measurement at the anatomical scan (180/7 and 236/7 weeks) before (period A, 2015-2017) and after (period B, 2017-2019) the introduction of universal transvaginal cervical length screening. Independent observers blindly evaluated the images obtained for cervical length using a qualitative scoring method based on five criteria, according to the Fetal Medicine Foundation.

RESULTS

In all, 6013 patients met the inclusion criteria, 3333 in period A and 2680 in period B. Maternal characteristics and risk factors for preterm birth were similar between the two periods. The acceptance of transvaginal cervical length measurement in period B was 95.5% in the overall cohort and 100% in the subgroup of high-risk patients. The quality score was significantly higher in period B than in period A. Among the image quality criteria, the anterior/posterior ratio, the correct magnification of the images, and the calipers' placement contributed significantly to the improved quality score in period B. Most of the sonographers performed better in period B, irrespective of the years of experience, but certificate holders obtained higher scores than non-certified sonographers, particularly those in mid-career. The identification of short cervix was significantly higher in period B than in period A.

CONCLUSION

The implementation of universal transvaginal cervical length screening and the certification process are associated with improved quality of cervical length images, even among expert sonographers and in the presence of anatomical pitfalls.

Comparison between trans-vaginal and trans-abdominal ultrasound examination of the cervix in the second trimester of pregnancy: a prospective study

OBJECTIVES

To compare transvaginal (TV) and trans-abdominal (TA) ultrasound assessment of cervical length (CL) at the time of the second-trimester scan for fetal anomalies.

METHODS

This was a prospective study including consecutive pregnant women attending the low-risk ultrasound clinic of two fetal medicine centres in Italy. The inclusion criteria were women between 19 + 0 and 22 + 0 weeks of gestation, attending the prenatal ultrasound clinic for the routine second trimester screening for fetal anomalies. The primary outcome was to compare the CL measurement obtained at TV compared to TA ultrasound; the secondary outcome was to report the inter and intra-observer variability of CL measured with the two different approaches. All women underwent TV and TA assessment of the cervix performed by two experienced certified operators, blinded to each other. Intra-class correlation coefficients (ICC) and Bland-Altman analyses were used to analyse the data.

RESULTS

Two hundred and fifty women were included in the analysis. All women had anteverted uterus. The mean gestational age at ultrasound was 20.7 ± 0.7 weeks; 1.2 % (3/250) scans were performed at 19 weeks, 49.2 % (123/250) at 20 weeks, 44.8 % (112/250) at 21 weeks and 4.8 % (12/250) at 22 weeks of gestations. Identification of the major landmarks of CL at TA ultrasound was achieved in all the included cases. There was good reliability between CL measured at TA (ICC 0.95, 95 % CI 0.93-0.97 for observer 1 and 0.92 %, 95 % CI 0.89-0.94 for observer 2) and TV ultrasound 0.97, 95 % CI 0.96-0.98 for observer 1 and 0.96, 95 % CI 0.95-0.97 for observer 2). There was also good reliability between the two observers for both the TA and TV assessment of the CL. Mean TA CL was 41.4 ± 5.5 for observer 1 and 40.5 ± 4.8 for observer 2 with no significant differences between the two measurements (mean difference 0.92 mm, 95 % CI -9.7 to 11.2). Likewise, there was no difference between the CL measured at TV ultrasound between the two observers (mean difference -0.83 mm, 95 % CI -5.97 to 4.30). Finally, there was no difference in the mean CL measured at TA compared to TV, either considering the overall population of women (mean difference: -0.43, 955 CI -8.65 to 7.79), or when stratifying the analysis according to the parity status and the operator.

CONCLUSIONS

Among experienced operators, there was no difference between TV and TA ultrasound assessment of the CL at the time of the routine anomaly scan for fetal anomaly.

Preterm Birth: Screening and Prediction

Preterm birth (PTB) affects approximately 10% of births globally each year and is the most significant direct cause of neonatal death and of long-term disability worldwide. Early identification of women at high risk of PTB is important, given the availability of evidence-based, effective screening modalities, which facilitate decision-making on preventative strategies, particularly transvaginal sonographic cervical length (CL) measurement. There is growing evidence that combining CL with quantitative fetal fibronectin (qfFN) and maternal risk factors in the extensively peer-reviewed and validated QUanititative Innovation in Predicting Preterm birth (QUiPP) application can aid both the triage of patients who present as emergencies with symptoms of preterm labor and high-risk asymptomatic women attending PTB surveillance clinics. The QUiPP app risk of delivery thus supports shared decision-making with patients on the need for increased outpatient surveillance, in-patient treatment for preterm labor or simply reassurance for those unlikely to deliver preterm. Effective triage of patients at preterm gestations is an obstetric clinical priority as correctly timed administration of antenatal corticosteroids will maximise their neonatal benefits. This review explores the predictive capacity of existing predictive tests for PTB in both singleton and multiple pregnancies, including the QUiPP app v.2. and discusses promising new research areas, which aim to predict PTB through cervical stiffness and elastography measurements, metabolomics, extracellular vesicles and artificial intelligence.

Ultrasonographic Transabdominal Measurement of Uterine Cervical Length for the Prediction of a Midtrimester Short Cervix

OBJECTIVE

This study was aimed to estimate the value of transabdominal (TA) ultrasound measurement of cervical length (CL), as an alternative of transvaginal (TV) ultrasound, for universal screening of short cervix in the midtrimester.

STUDY DESIGN

We conducted a prospective cohort study of nulliparous women with singleton pregnancy at 20 to 24 weeks of gestation. All participants underwent TA ultrasound followed by TV ultrasound with acquisitions of images and videos of the uterine cervix. A second sonographer, blinded to the participants' data and pregnancy outcomes, measured the CL using TA and TV images and videos. Pearson's correlation test and receiver operating characteristic (ROC) curve analyses were performed.

RESULTS

A total of 805 participants were recruited, including 780 (97%) where TA CL measurement was feasible. We observed a strong correlation of CL between TA and TV (correlation coefficient: 0.57; p < 0.0001) with a mean TA measurement being 4 mm (95% confidence interval [CI]: -6 to 14 mm) below the mean TV measurement (mean of differences: 5 ± 4 mm). We observed that a TA CL <30 mm was highly predictive of a short cervix defined as a TV CL ≤25 mm (area under the ROC curve: 0.97; 95% CI: 0.95-0.99; p < 0.0001) with a sensitivity of 100% and a false-positive rate of 22%.

CONCLUSION

Universal short cervix screening in nulliparous women could be performed using TA ultrasound, which could allow the avoidance of TV ultrasound in more than three quarter of women. In low-risk population, TV ultrasound could be reserved to women with TA CL <30 mm.

KEY POINTS

· Cervical length (CL) measurement with transabdominal (TA) ultrasound is feasible in most cases and is strongly correlated with CL measured with transvaginal (TV) ultrasound.. · Using a cut-off of 30 mm for TA ultrasound as a first-step screening of short cervix in nulliparous women, three-quarter of TV ultrasound could have been avoided.. · Use of TA CL screening could alleviate some of the logistical challenges of universal TV CL screening..

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 perceptions of pregnant women about cervical length screening for preterm birth prevention

BACKGROUND

The Western Australian Preterm Birth Prevention Initiative was officially launched in November 2014. It demonstrated an initial decrease in the preterm birth rate in Western Australia. One of the key points of this initiative is the routine ultrasound measurement of the cervical length in mid-pregnancy.

AIM

The aim of this study was to evaluate the perceptions and attitudes of Western Australian women regarding transvaginal cervical length (TVCL) screening for preterm birth prevention.

MATERIALS AND METHODS

Self-administered questionnaires were completed by pregnant women before and after their mid-trimester obstetric ultrasound. Maternal demographical and medical data were collected in addition to opinions of TVCL screening.

RESULTS

A total of 598 women participated with the maternal age range representative of the Western Australian obstetric population. There was a high rate of acceptance of TVCL imaging, with 2% of the 149 women declining a transvaginal ultrasound (TVU) offered in this study, 1.5% refusing a TVU in the past and 5.7% reporting that they would have a concern in having a TVU in the future. Women stated that they either had declined TVCL in the past (11%) or would decline in the future (30.7%) as they wanted to discuss the procedure with their clinician first, had been advised not to have a TVU by their clinician (11% in the past and 47.7% in the future) or felt uncomfortable with the operator (22% at a previous TVU and 34.4% in the future).

CONCLUSION

Pregnant women participating in this study had a high acceptance of TVCL screening for preterm birth prevention.

Comparison of transabdominal and transvaginal ultrasonography for the assessment of cervical length in the third trimester of pregnancy

OBJECTIVE

This study aimed to compare TA and transvaginal (TV) ultrasound assessment of cervical length (CL), as well as to assess the feasibility of the TA approach in the third trimester of pregnancy.

MATERIALS AND METHODS

This was prospective study of low-risk women at 31-34 gestational weeks who underwent TA and TV CL measurements during a routine 3rd trimester scan. All examinations were performed by one operator who was blind to the measurements. Differences between the two methods were evaluated.

RESULTS

240 women were initially enrolled in the study. Paired TA and TV measurements were obtained in 123 (51.3%) women. The mean TV CL was 35.2 ± 6.8 mm and the mean TA CL was 34.7 ± 6.5 mm. There was a significant correlation between the CL measured by the two different methods (r = 0.816). No significant differences were identified between the mean CL measurements of the two techniques (t = -1.360; p = 0.176). Moreover, regarding the feasibility of TA technique, it was less likely to obtain TA CL images in cases with a cephalic fetal presentation (p = 0.028).

CONCLUSION

At 31-34 gestational weeks, with an empty bladder, the cervix can be visualized by the TA approach in only about half of the cases (51.3%). The TA CL measurements show a significant correlation with the TV ones. More research is needed to determine the potential predictive value of the TA ultrasound for preterm labor.

Transperineal versus transvaginal sonographic measurements of cervical length in pregnant women between 16 and 24 weeks of gestation

PURPOSE

To investigate the correlation between cervical length measurements using transvaginal and transperineal approaches at 16-24 weeks of gestation.

METHODS

The prospective study recruited 110 singleton pregnant women. All the measurements were performed by one operator who was blinded to the results of both approaches. Cervical length was first measured by transvaginal sonography (TVUS) then transperineal sonography (TPUS). The transvaginal approach was used as the reference measurement. Patient preference regarding the sonographic approaches was evaluated using questionnaire.

RESULTS

Cervical length was successfully measured by TVUS in all cases. TPUS was successful in 108/110 participants. There was high correlation between the results of TVUS and TPUS (Pearson's correlation coefficient was .94; 95% CI .9 to .95. Lin's concordance correlation coefficient was .94; 95% CI .92-.96). The estimated difference in cervical length measured using TVUS and TPUS was .2 mm. The 95% tolerance interval for paired observation was -1.8 to 2.3 mm. The interobserver coefficient of TPUS measurement was .98 (95% CI .92-.99). TPUS was rated as resulting in mild or no discomfort and was preferred by most women.

CONCLUSION

TVUS and TPUS techniques showed high correlation in cervical length measurement with high interobserver reliability. More patients preferred TPUS. TPUS should be considered as an alternative method of cervical length measurement.

Diagnostic accuracy of cervical elastography in predicting preterm delivery: A systematic review and meta-analysis

BACKGROUND

The aim of the study was to evaluate the diagnostic accuracy of cervical elastography in predicting preterm delivery (PTD).

METHODS

We searched the PubMed, EMBASE, and Cochrane databases to identify relevant studies that applied ultrasound (US) elastography to assess cervical stiffness and predict PTD. All the studies were published before December 11, 2018, and only studies published in English were collected. The cervical length (CL) was considered a comparator, and the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool was applied to assess the quality of the included studies. Summary receiver operating characteristic (SROC) modeling was performed to evaluate the diagnostic performance of cervical elastography in predicting PTD. Subgroup analyses were also performed.

RESULTS

Seven studies, including 1488 pregnant women, were included in this meta-analysis. Cervical elastography showed a summary sensitivity of 0.84 [95% confidence interval (CI): 0.68, 0.93], a specificity of 0.82 (95% CI: 0.63, 0.93), a diagnostic odds ratio of 25 (95% CI: 7, 93), and an area under the curve (AUC) of SROC of 0.90 (95% CI: 0.87-0.93). CL measurement showed that the AUC of SROC was 0.60 (95% CI: 0.56-0.64). The results of subgroup analysis showed that the summary sensitivity and specificity were different in the QUADAS-2 score subgroups.

CONCLUSION

Cervical elastography is a promising and reliable method to predict PTD. Cervical elastography showed better diagnostic performance to predict PTD than CL measurement.

Cervical length measurement in nulliparous women at term by ultrasound & its relationship to spontaneous onset of labour

Background & objectives:

Data on serial cervical length (CL) measurements in pregnancy at term to predict spontaneous labour onset are scarce and conflicting. This study was conducted to observe CL changes preceding spontaneous onset of labour, by serial transvaginal sonography (TVS) and transabdominal sonography (TAS), in nulliparous Indian women near term.

Methods:

Only nulliparous women with a singleton foetus in cephalic presentation and who confirmed their gestational age were recruited. Sonographic CL measurements were taken at weekly intervals from 36 wk gestation onwards by a single ultrasonologist. Transabdominal and transvaginal measurements were undertaken using the suitable transducer probes with the women in the supine position.

Results:

A total of 104 women with spontaneous onset of labour were evaluated. There was substantial variation in CL measurements, both by TVS and by TAS, from 36 to 40 wk gestation, although the two sets of measurements correlated closely. Mean CL changed significantly over the last three weeks before delivery. However, only one-third of the women showed CL change of >5 mm per week in the last three weeks. There was poor correlation between gestational age at delivery and the last measured CL, either by TVS or TAS. Length >3.1 mm, measured by TVS at 38 wk gestation, predicted post-dated pregnancy to a limited extent.

Interpretation & conclusions:

Inter-individual variations in CL and in CL changes were large. Thus, it was not practical to predict spontaneous onset of labour by sonographic CL measurement near term. Post-dated pregnancy may be predicted with limited success. Further studies should explore other parameters, in addition to CL.

Implementing universal cervical length screening in asymptomatic women with singleton pregnancies: challenges and opportunities

Cervical length (CL) screening has been successfully utilised to identify asymptomatic women, with a singleton pregnancy, at risk of preterm birth (PTB), thereby providing an opportunity to offer interventions that may reduce that risk. Cervical length screening with ultrasound is most effectively performed with a transvaginal approach. Universal cervical length screening, encompassing all singleton pregnancies rather than restricting screening to those considered at increased risk of PTB, is currently not widely used, despite a growing body of evidence in support of its utility for PTB prevention. There are a number of barriers that may prevent or restrict the implementation of a universal CL screening program. These include cost, availability of vaginal progesterone and other treatment options, reluctance of women to undergo transvaginal ultrasound and the perceptions and beliefs of medical practitioners. Given that mid-pregnancy CL measurement is a recognised predictor of spontaneous PTB, that most cases of PTB occur with no prior maternal history and that there are interventions available that may reduce the risk of PTB, we believe there is a clear role for routine CL screening to be adopted as a component of the fetal morphology ultrasound examination. As a strategy to reduce PTB rates, discussion and counselling about PTB prevention and CL screening should be adopted as a core element of prenatal care.

Transabdominal ultrasound is appropriate

Preterm birth remains a major cause of perinatal morbidity and mortality. A short cervix is strongly associated with spontaneous preterm birth. Professional organizations support cervical length screening for singleton gestations with a prior spontaneous preterm birth and second-trimester cervical length measurements between 16-24 weeks. All interventions used to decrease the risk of preterm birth in women with a short cervix are based on clinical trials that used transvaginal cervical length measurement, but transabdominal ultrasound has been shown to correlate well with transvaginal measurement in some observational studies. Transvaginal cervical length measurement is more accurate and more reliably obtained than the transabdominal approach. Conversely, transabdominal ultrasound could have the advantage of ease of implementation and, in general, is perceived by patients to be associated with less discomfort. Currently, there is no randomized clinical study that compares head-to-head the effectiveness of transvaginal vs transabdominal ultrasound for preterm birth risk screening. This point/counterpoint article summarizes the pros and cons of the 2 ultrasound approaches and debates whether transvaginal ultrasound should be used exclusively or if transabdominal ultrasound can be incorporated in cervical length screening for prevention of preterm birth.

Not transabdominal!

Preterm birth remains a major cause of perinatal morbidity and mortality. A short cervix is strongly associated with spontaneous preterm birth. Professional organizations support cervical length screening for singleton gestations with a prior spontaneous preterm birth and second-trimester cervical length measurements between 16-24 weeks. All interventions used to decrease the risk of preterm birth in women with a short cervix are based on clinical trials that used transvaginal cervical length measurement, but transabdominal ultrasound has been shown to correlate well with transvaginal measurement in some observational studies. Transvaginal cervical length measurement is more accurate and more reliably obtained than the transabdominal approach. Conversely, transabdominal ultrasound could have the advantage of ease of implementation and, in general, is perceived by patients to be associated with less discomfort. Currently, there is no randomized clinical study that compares head-to-head the effectiveness of transvaginal vs transabdominal ultrasound for preterm birth risk screening. This point/counterpoint article summarizes the pros and cons of the 2 ultrasound approaches and debates whether transvaginal ultrasound should be used exclusively or if transabdominal ultrasound can be incorporated in cervical length screening for prevention of preterm birth.

Comparison of transabdominal and transvaginal ultrasonography for the assessment of cervical length at 16-23 weeks of gestation

The aim of this study was to assess the relationship between transabdominal and transvaginal ultrasonography for the cervical length assessment and to evaluate the predictive value of the transabdominal ultrasonography cervical length assessment for predicting preterm birth. A prospective cohort study was conducted. Transabdominal and transvaginal ultrasonography cervical length assessments were performed in 160 pregnant women between 16 and 23 ^+ 6 weeks of gestation. Transabdominal ultrasonography cervical length assessment was positively correlated with the transvaginal ultrasonography cervical length assessment. Mean ± standard deviation of the cervical length was significantly different between transabdominal and transvaginal ultrasonography (36.4 ± 5.4 vs. 41.2 ± 5.4 mm, p < .001). Transabdominal cervical length was shorter than the transvaginal cervical length with a mean difference of 4.8 mm. The sensitivity, specificity, positive predictive value and negative predictive value for predicting preterm birth when the transabdominal cervical length was ≤35 mm, were 50%, 52.1%, 9.1%, and 91.6%, respectively. In conclusion, transabdominal ultrasonography cervical length assessment is positively correlated with the transvaginal ultrasonography cervical length assessment. Transabdominal cervical length assessment was not a good predictor of preterm birth.

The role of routine cervical length screening in selected high- and low-risk women for preterm birth prevention

Preterm birth remains a major cause of neonatal death and short and long-term disability in the US and across the world. The majority of preterm births are spontaneous and cervical length screening is one tool that can be utilized to identify women at increased risk who may be candidates for preventive interventions. The purpose of this document is to review the indications and rationale for CL screening to prevent preterm birth in various clinical scenarios. The Society for Maternal-Fetal Medicine recommends (1) routine transvaginal cervical length screening for women with singleton pregnancy and history of prior spontaneous preterm birth (grade 1A); (2) routine transvaginal cervical length screening not be performed for women with cervical cerclage, multiple gestation, preterm premature rupture of membranes, or placenta previa (grade 2B); (3) practitioners who decide to implement universal cervical length screening follow strict guidelines (grade 2B); (4) sonographers and/or practitioners receive specific training in the acquisition and interpretation of cervical imaging during pregnancy (grade 2B).

Sonographic Methods of Evaluating Cervical Length: A Literature Review

Labor that begins between 20 and 37 weeks gestation is appropriately termed preterm labor. Some of the precipitating factors of preterm labor are changes in cervical status including dilatation and effacement. Until recently, a digital pelvic examination was considered the gold standard for evaluating cervical changes. Current research promotes the use of sonography for the prediction of preterm labor. It is essential for sonographers to become familiar with the various methods of cervical imaging including transabdominal, translabial, and transvaginal approaches. Each technique has its costs and benefits; however, a review of the current literature will show that the transvaginal method of cervical measurement is the most reliable.

Universal cervical length screening in singleton gestations without a previous preterm birth: ten reasons why it should be implemented

A short cervix is associated strongly with preterm birth. Pharmacologic intervention with vaginal progesterone in women with a singleton pregnancy and a short cervix in the second trimester decreases the incidence of preterm birth. We explore the evidence that universal cervical length screening in women with a singleton pregnancy meets the criteria for an effective screening test for preterm birth prevention, driving it towards becoming routinely offered in prenatal care.

Correlation Between Cervical Lengths Measured by Transabdominal and Transvaginal Sonography for Predicting Preterm Birth

OBJECTIVES

Cervical length assessment is important for predicting preterm birth. Cervical length measurement using transabdominal sonography is more comfortable for the patient but has more limitations than transvaginal sonography. Our aim was to determine whether transabdominal sonography could identify those women who should undergo transvaginal sonography for prediction of preterm birth.

METHODS

In this prospective study, women underwent cervical length measurements by transabdominal and transvaginal sonography between 20 and 29 gestational weeks and were followed until delivery. We assessed whether short cervical lengths on transabdominal sonography could predict short cervical lengths on transvaginal sonography and whether these measurements could predict preterm births (<34 gestational weeks).

RESULTS

The mean cervical lengths were not significantly different between the techniques (mean ± SD, 3.78 ± 0.82 and 3.82 ± 0.77 cm on transabdominal and transvaginal sonography, respectively; P = .09). The sensitivity of short cervical lengths (<2 cm) on transabdominal sonography for prediction of short cervical lengths on transvaginal sonography was 100%. The sensitivity, specificity, positive predictive value, negative predictive value, and relative risk of short cervical lengths (<2 cm) for predicting preterm birth were 21.4%, 98.68%, 50.00%, 95.32%, and 13.22 when using transabdominal sonography and 28.57%, 94.94%, 66.6%, 95.74%, and 17.78 when using transvaginal sonography, respectively. In an analysis that included cases with transabdominal sonography, the sensitivity of short cervical lengths for predicting preterm birth was increased.

CONCLUSIONS

Women whose cervical lengths are measurable and long on transabdominal sonography may not need transvaginal sonography. Women whose cervical lengths are unmeasurable or short (<2 or <2.5 cm) on transabdominal sonography should undergo transvaginal sonography to measure cervical lengths for prediction of preterm birth.

Uterine fibroids at routine second-trimester ultrasound survey and risk of sonographic short cervix

OBJECTIVE

To determine whether women with sonographically identified uterine fibroids are at higher risk for a short cervix.

METHODS

This retrospective cohort study evaluated all women with singleton gestations who had a routine second-trimester ultrasound at 17-23 weeks gestational age from 2010 to 2013. When fibroids were noted, their presence, number, location and size were recorded. Exclusion criteria included a history of cervical conization or loop electrosurgical excision procedure (LEEP), uterine anomalies, maternal age greater than 40 years, and a previously placed cerclage. The primary variable of interest was short cervix (<25 mm). Secondary variables of interest included gestational age at delivery, mode of delivery, indication for cesarean, malpresentation, birth weight, and Apgar scores. A multivariable logistic regression analysis was performed.

RESULTS

Fibroids were identified in 522/10 314 patients (5.1%). In the final multivariable logistic regression model, short cervix was increased in women with fibroids (OR 2.29, 95% CI: 1.40, 3.74). The number of fibroids did not affect the frequency of short cervix. Fibroids were significantly associated with preterm delivery (<37 weeks), primary cesarean, breech presentation, lower birth weight infants, and lower Apgar scores.

CONCLUSIONS

Women with uterine fibroids may be at higher risk for a short cervix. Fibroids are also associated with several adverse obstetric and neonatal outcomes.

Cervical length measurement: Comparison of transabdominal and transvaginal approach

Objective: To compare transabdominal (TA) and transvaginal (TV) ultrasound assessment of cervical length at 16–41 weeks gestation.

Methods: TA and TV ultrasound measurements of cervical length were made on 491 pregnancies of 16–41 weeks gestation. Cervical length was measured from internal to external cervical os. Bland‐Altman plots and Wilcoxon signed rank test were used to evaluate differences between TA and TV measurements.

Results: The validity of the TA method depended on cervical length. Although the TA method underestimated cervical length by 2.0 mm on average (P < 0.001), Bland Altman plots showed an inverse trend with shorter cervixes. In women with a cervix < 25 mm (n = 30) based on TV scan measurement, TA overestimated cervical length by 12 mm (P < 0.001). The sensitivity and specificity of TA as a test to detect cervical length < 25 mm were 10% (95% CI: 2.1–26%) and 94% (95% CI: 92–96%) respectively; the negative LR was 0.96 (95% CI: 0.84–1.08). The maximum area under the ROC curve would be obtained at a TA cut‐off = 32 mm (to detect a cervix < 25 mm), corresponding to a sensitivity of 77% and a specificity of 58%.

Conclusion: TA measurements do not reflect TV assessment accurately, particularly if the cervix is short. At 24–34 weeks, a policy of proceeding to TV scan if TA measurement is < 25 mm will only detect 10% of affected pregnancies and has a poor positive predictive value so is of limited value as a predictive tool for women attending with symptoms and signs of preterm labour > 24 weeks gestation. There is no value in TA assessment of the cervix > 36 weeks.

Prospective evaluation of a protocol for using transabdominal ultrasound to screen for short cervix

OBJECTIVE

We sought to evaluate a recently proposed protocol whereby transabdominal ultrasound of the cervix might be used as a prescreen to select women to undergo or to forgo measurement of cervical length via transvaginal ultrasound (CLvag).

STUDY DESIGN

This was a prospective cohort study. Measurements of cervical length via transabdominal ultrasound (CLabd) and CLvag were made in women with singleton pregnancy during routine obstetrical ultrasound examination at 18(0/7) to 23(6/7) weeks of gestation. The transabdominal screen was considered positive if CLabd was ≤36 mm with the maternal bladder full or ≤35 mm with the bladder empty, or adequate imaging of the cervix could not be obtained. Sensitivity, specificity, predictive values, and likelihood ratios of a positive screen to detect a short cervix (CLvag ≤25 mm) were calculated.

RESULTS

An interim analysis identified several technical problems with CLabd measurements, so the protocol was extensively revised. Under the revised protocol, 1580 women were included. Adequate views of the cervix were obtained via transabdominal imaging in 46% of subjects with the bladder empty and 56% with the bladder full. The correlation between CLabd and CLvag was poor (r = 0.38). Of the 17 patients with a short cervix, 15 had suboptimal transabdominal exams (screen positive) and 2 had CLabd ≤35 mm with bladder empty (screen positive). Sensitivity of the screen was 100% (95% confidence interval, 80.5-100%) but specificity was only 32.2% (95% confidence interval, 29.9-34.6%) and screen positive rate was 66.3%. Several technical problems and limitations of transabdominal imaging of the cervix are shown.

CONCLUSION

Using modern, high-resolution ultrasound equipment, we were unable to adequately image the cervix via transabdominal ultrasound in half the cases. Although we confirmed that a CLabd cutoff value of 35-36 mm is appropriate for detection of short cervix, the technique for measuring CLabd is fraught with technical problems. Practitioners must validate the technique in their own practice before adopting this or similar prescreening protocols. We decided not to adopt this protocol.

Transvaginal cervical length and amniotic fluid index: can it predict delivery latency following preterm premature rupture of membranes?

OBJECTIVE

We sought to determine whether transvaginal cervical length (TVCL), amniotic fluid index (AFI), or a combination of both can predict delivery latency within 7 days in women presenting with preterm premature rupture of membranes (PPROM).

STUDY DESIGN

This was a prospective observational study of TVCL measurements in 106 singleton pregnancies with PPROM between 23-33 weeks. Delivery latency was defined as the period (in days) from the initial TVCL after PPROM to delivery of the infant, with our primary outcome being delivery within 7 days of TVCL. The independent predictability of significant characteristics for delivery within 7 days was determined using multiple logistic regression. Sensitivity, specificity, and predictive values were used to examine whether the presence of a short TVCL, AFI, or a combination of both affected the risk of delivery within 7 days.

RESULTS

Delivery within 7 days occurred in 51/106 (48%) of pregnancies. Median duration (interquartile range) from PPROM to delivery and TVCL to delivery was 8 days (4.0-16.0) and 8 days (3.0-15.0), respectively. Using multiple regression TVCL as a continuous variable (odds ratio, 0.65; 95% confidence interval, 0.44-0.97; P < .05), AFI ≤5 cm (odds ratio, 4.69; 95% confidence interval, 1.58-13.93; P < .01) were determined to be independent predictors of delivery within 7 days. In all, 42 women (40%) had a TVCL ≤2 cm, while 62 (59%) had AFI ≤5 cm. A total of 26 women (25%) had a combination of both TVCL ≤2 cm and AFI ≤5 cm, while 28 women (27%) had neither characteristic. The predictive value of delivery within 7 days for a TVCL ≤2 cm was 62%, and for an AFI ≤5 cm was 58%. Having a combination of low TVCL and low AFI did not increase the predictive value of delivery within 7 days (58%). In contrast, only 3 of 27 women (11%) with neither characteristic delivered within 7 days. The predictive value of delivery >7 days for TVCL >2 cm alone was 61%. This predictive value changed when analyzed in conjunction with an AFI ≤5 cm and >5 cm at 42% and 89%, respectively.

CONCLUSION

A shorter TVCL and an AFI ≤5 cm independently predict delivery within 7 days in women presenting with PPROM. The combination of an AFI >5 cm and TVCL >2 cm greatly improved the potential to remain undelivered at 7 days following cervical length assessment. These findings may be helpful for counseling and optimizing maternal and neonatal care in women with PPROM.

Is transabdominal ultrasound scanning of cervical measurement in mid-trimester pregnancy a useful alternative to transvaginal ultrasound scan?

OBJECTIVE

The aim of this study is to assess the correlation between transabdominal and transvaginal ultrasound measurements of the cervix in pregnancy. If transabdominal ultrasound measurement of cervical length is found to provide effective information, it could be used in patient counselling and when making clinical decisions.

MATERIAL AND METHODS

One hundred and twenty seven pregnant patients between 18-26 weeks of pregnancy were enrolled in this prospective study for measuring cervical length, both by transabdominal and transvaginal ultrasound scan after bladder emptying. Transabdominal and transvaginal measurements were compared and correlated.

RESULTS

In patients with transvaginal ultrasound scan (TVS) cervical length ≤32 mm, TVS cervical length was found to be shorter than by transabdominal ultrasound scan (TAS). Most of these patients needed >3 cm of vertical pocket of urine in the bladder for adequate visualisation of the cervix. In patients with TVS cervical length >32 mm, the TVS measurement of the cervix was longer than the TAS measurement of the cervix. In these patients, the cervix could be seen by TAS when there was either ≤3 cm vertical pocket of urine in the bladder or an empty bladder. Statistical tests showed that there is a significant difference between TAS and TVS cervical measurements and that there is a significant association between these two measurements.

CONCLUSION

Most of the patients needed variable degrees of bladder filling for adequate visualisation of the cervix. Although minimal bladder filling does not influence TAS measurements of cervical length, moderate fullness of the bladder does cause an apparent increase in TAS measurements of cervical length. If the cervical length is ≥30 mm by TAS, regardless of urine content in the bladder, the patient can be assured vis a vis their risk of preterm labour as far as cervical length is concerned. However, in patients with TAS cervical measurement <30 mm and where the bladder needed a moderate amount of urine for adequate visualisation of the cervix, TVS cervical measurement may be close to the critical value of 25 mm. These patients need to be counselled and offered TVS for better assessment of cervical length.

Cost-effectiveness of transabdominal ultrasound for cervical length screening for preterm birth prevention

OBJECTIVE

Transabdominal ultrasound (TAUS) cervical length (CL) screening has been proposed as an alternative to universal transvaginal screening to identify women at an increased risk of preterm birth. We sought to identify whether and under what circumstances TAUS would be cost-effective.

STUDY DESIGN

This is a decision analytic model designed to compare an initial TAUS CL screening approach with universal transvaginal screening in a hypothetical cohort of women with a singleton pregnancy. Cost, probability, and utility estimates were derived from the existing literature.

RESULTS

Under baseline assumptions, universal transvaginal was the dominant strategy. In comparison to TAUS, universal transvaginal CL screening reduced preterm birth by 0.03%, reduced costs by $1.2 million and increased quality-adjusted life years by 70 per 100,000 women. Although robust to many changes in many estimates, the model was sensitive to the cost of a transvaginal ultrasound, the prevalence of a short cervix and the test characteristics (ie, sensitivity and specificity) of a TAUS screening examination for short CL.

CONCLUSION

Compared with an initial TAUS screen, universal transvaginal ultrasound was a more cost-effective strategy under most assumptions. Optimizing TAUS testing characteristics or applying a transabdominal screening strategy in lower risk populations may yield an initial TAUS to be cost-effective.

Comparison of cervical lengths using transabdominal and transvaginal sonography in midpregnancy

OBJECTIVES

Cervical length assessment is helpful to predict and prevent preterm birth. However, transvaginal sonography is not easy to perform. The aim of this study was to investigate the relationship and discrepancies between cervical lengths measured by transabdominal and transvaginal sonography in midpregnancy.

METHODS

Transabdominal and transvaginal cervical lengths were measured in 255 pregnant women between 20 and 29 gestational weeks. The discrepancies in cervical lengths between the two methods were analyzed for the following maternal and fetal conditions: (1) vertex versus breech fetal presentation, (2) whether the fetal presenting part overlay the cervical internal os, (3) whether both the internal os and external os were visible or only the internal os was clearly visible, (4) maternal bladder filling status, (5) maternal age, (6) parity, and (7) gestational age.

RESULTS

The mean cervical lengths were not significantly different (mean ± SD, 3.88 ± 0.73 cm on transabdominal sonography and 3.93 ± 0.72 cm on transvaginal sonography; P = .129; Pearson r = 0.75). The 5th-percentile transabdominal cervical length was 26.0 mm, and the transvaginal length was 27.8 mm. There were significant discrepancies between the two methods in the cases in which a fetal presenting part overlay the internal os, in the cases in which the external os was not clearly visible, and in primiparous women. Transabdominal cervical measurements were consistently shorter than transvaginal measurements in the cases with discrepancies.

CONCLUSIONS

Transabdominal cervical length measurements are correlated with transvaginal measurements overall, and the transabdominal length is consistently shorter than the transvaginal length in cases with discrepancies. Transabdominal sonography could be used as a cervical length screening tool.

Can transabdominal ultrasound identify women at high risk for short cervical length?

OBJECTIVE

To determine whether transabdominal cervical length screening could identify women at high risk for having a short cervix on transvaginal ultrasound.

DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

POPULATION

A total of 703 patients with a singleton pregnancy at 18 to 23(+6) weeks of gestation who underwent transabdominal and transvaginal cervical length assessment during anatomy ultrasound at a single institution between January 2007 and October 2011.

METHODS

Electronic medical records were reviewed to identify women who met the study criteria.

MAIN OUTCOME MEASURES

The primary outcome was the number of women with a short transabdominal cervical length (defined as ≤ 30 mm) who needed to undergo transvaginal ultrasound to detect one woman with a short transvaginal cervical length of ≤ 20 mm.

RESULTS

In all, 703 patients were included in the primary analysis; 3.42 women with transabdominal cervical length ≤ 30 mm needed to undergo transvaginal ultrasound to detect one woman with transvaginal ultrasound cervical length ≤ 20 mm. Of women with short transvaginal cervical length ≤ 20 mm, 89.8% had a transabdominal measurement ≤ 30 mm and 96.7% had a transabdominal measurement ≤ 33 mm.

CONCLUSIONS

Screening of transabdominal cervical length may represent a useful strategy for detecting women with short cervix on transvaginal ultrasound.

Can transabdominal ultrasound be used as a screening test for short cervical length?

OBJECTIVE

Universal transvaginal cervical length screening can be associated with a significant logistical burden. We hypothesized that there is a threshold cervical length measured by transabdominal ultrasound above which risk for short transvaginal cervical length is extremely low.

STUDY DESIGN

This prospective cohort study evaluated a consecutive series of women offered universal transvaginal cervical length screening during anatomy ultrasound. Transabdominal measurement of the cervix-obtained before and after voiding for each patient-was performed before transvaginal ultrasound. The study was powered to detect a transabdominal cervical length cutoff with 95% sensitivity (95% confidence interval, 90-99%) for transvaginal cervical length of ≤25 mm.

RESULTS

One thousand two hundred seventeen women were included in the analysis. Prevoid transabdominal cervical length ≤36 mm detects 96% of transvaginal cervical lengths ≤25 mm with 39% specificity. A prevoid transabdominal cervical length ≤35 mm detects 100% of transvaginal cervical lengths ≤20 mm with 41% specificity. Transabdominal images of the cervix could not be obtained in 6.2% of women prevoid and 17.9% of women postvoid.

CONCLUSION

Transabdominal cervical length screening successfully identifies women at very low risk for short transvaginal cervical length. Transabdominal screening may significantly reduce the burden of universal cervical length screening by allowing approximately 40% of women to avoid transvaginal ultrasound. To ensure high sensitivity of transabdominal screening, approximately 60% of patients will still require a transvaginal study.

A blueprint for the prevention of preterm birth: vaginal progesterone in women with a short cervix

Preterm birth is the leading cause of perinatal morbidity and mortality worldwide, and is the most important challenge to modern obstetrics. A major obstacle has been that preterm birth is treated (implicitly or explicitly) as a single condition. Two thirds of preterm births occur after the spontaneous onset of labor, and the remaining one third after "indicated" preterm birth; however, the causes of spontaneous preterm labor and "indicated" preterm birth are different. Spontaneous preterm birth is a syndrome caused by multiple etiologies, one of which is a decline in progesterone action, which induces cervical ripening. A sonographic short cervix (identified in the midtrimester) is a powerful predictor of spontaneous preterm delivery. Randomized clinical trials and individual patient meta-analyses have shown that vaginal progesterone reduces the rate of preterm delivery at <33 weeks of gestation by 44%, along with the rate of admission to the neonatal intensive care unit, respiratory distress syndrome, requirement for mechanical ventilation, and composite neonatal morbidity/mortality score. There is no evidence that 17-α-hydroxyprogesterone caproate can reduce the rate of preterm delivery in women with a short cervix, and therefore, the compound of choice is natural progesterone (not the synthetic progestin). Routine assessment of the risk of preterm birth with cervical ultrasound coupled with vaginal progesterone for women with a short cervix is cost-effective, and the implementation of such a policy is urgently needed. Vaginal progesterone is as effective as cervical cerclage in reducing the rate of preterm delivery in women with a singleton gestation, history of preterm birth, and a short cervix (<25 mm).

Assessment of cervical length and the relationship between short cervix and preterm birth

Premature effacement of the cervix, or short cervix, in the midtrimester of pregnancy currently represents the strongest predictor of spontaneous preterm birth. Numerous studies have examined the relationship between short cervix and preterm birth, and although differences in sensitivity and predictive value exist, the overwhelming consensus indicates that the risk of preterm birth increases with decreasing cervical length. Cutoff values for cervical length range from less than 25 mm to less than 15 mm depending on patient characteristics and gestational age. Importantly, short cervix is more sensitive for predicting earlier forms of prematurity (at <32 weeks) than later forms of prematurity (>32 weeks). Cervical length measured at 18 to 24 weeks' gestation appears to be the most valuable measurement. Cervical length assessments can be performed by digital examination, a cervical measurement device, transabdominal ultrasound, or transvaginal ultrasound. Transvaginal ultrasound is the most reliable method to evaluate cervical length, but it is not available in all locations. Current clinical practice standards do not recommend universal screening for cervical length; however, results of randomized controlled clinical trials provide evidence to support expanded screening programs by individual practitioners.

Transabdominal evaluation of uterine cervical length during pregnancy fails to identify a substantial number of women with a short cervix

OBJECTIVE

To assess the diagnostic performance of transabdominal sonographic measurement of cervical length in identifying patients with a short cervix.

METHODS

Cervical length was measured in 220 pregnant women using transabdominal and transvaginal ultrasound (US). Reproducibility and agreement between and within both methods were assessed. The diagnostic accuracy of transabdominal US for identifying cases with a cervical length <25 mm was evaluated.

RESULTS

Twenty-one out of 220 cases (9.5%) had a cervical length <25 mm by transvaginal US. Only 43% (n = 9) of patients with a short cervix were correctly identified by transabdominal US. In patients with a cervical length of <25 mm by transvaginal US, transabdominal measurement of the cervix overestimated this parameter by an average of 8 mm (95% LOAs, -26.4 to 10.5 mm). Among women without a short cervix, transabdominal US underestimated cervical length on average (LOA) by 1.1 mm (95% LOAs, -11.0 to 13.2 mm). Transvaginal US was also more reproducible (intraclass correlation coefficient: (ICC) (0.96; 95% CI, 0.94 to 0.97) based on comparisons between 2D images and immediately acquired 3D volume datasets relative to transabdominal US (ICC: 0.71; 95% CI, 0.57 to 0.84). Transvaginal US detected 13 cases with funneling and six cases with sludge whereas only three cases of funneling and one of sludge were detected by transabdominal US.

CONCLUSION

Transabdominal measurement overestimated cervical LOA by 8 mm among women with a short cervix and resulted in the underdiagnosis of 57% of cases.

Universal maternal cervical length screening during the second trimester: pros and cons of a strategy to identify women at risk of spontaneous preterm delivery

Three large randomized controlled trials investigating the efficacy of universal cervical length screening and treatment with vaginal progesterone or cervical cerclage to prevent preterm delivery have been published over the past several years. None of these trials demonstrate proven efficacy for universal cervical length screening and cerclage placement in women with short cervical length. However, universal cervical length screening and treatment with daily vaginal progesterone in women with short cervical length reduces the risk of preterm birth, but large numbers of women must be screened to prevent a relatively small number of preterm deliveries. Issues that should be considered while implementing universal cervical length screening include: (1) standards of quality and reproducibility for transvaginal ultrasound cervical length ascertainment; (2) implications of screening on the application of therapeutic strategies to populations not known to benefit (so-called "indication creep"); and (3) willingness of obstetricians to prescribe vaginal progesterone formulations that are not approved by the US Food and Drug Administration for preterm birth prevention. Optimal strategies to employ cervical ultrasound and progesterone treatment might be revealed by additional studies investigating cervical length cutoffs, frequency of screening, selective screening in higher-risk groups, and the use of transabdominal cervical length screening as a surrogate for transvaginal cervical length screening.

SOGC Clinical Practice Guideline. Ultrasonographic cervical length assessment in predicting preterm birth in singleton pregnancies

OBJECTIVES

To review (1) the use of ultrasonographic-derived cervical length measurement in predicting preterm birth and (2) interventions associated with a short cervical length.

OUTCOMES

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

EVIDENCE

Published literature was retrieved through searches of PubMed and The Cochrane Library up to December 2009, using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, incompetent cervix, 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 and health technology assessment-related 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 and the Maternal Fetal Medicine Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made according to the guidelines developed by The Canadian Task Force on Preventive Health Care (Table 1).

BENEFITS, HARMS, AND COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the ultrasonographic 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.

SPONSORS

The Society of Obstetricians and Gynaecologists of Canada.

Sonographic cervical length measurement in pregnant women with a cervical pessary

OBJECTIVES

The aims of this study were to describe and assess the feasibility of measuring cervical length by standard transvaginal sonography (TVS) and transperineal sonography (TPS) in women with a cervical pessary and compare these measurements with those obtained with a new transvaginal technique.

METHODS

Measurement of cervical length by TPS was attempted immediately before measurement using TVS in 48 women with a cervical pessary at between 22 and 23 weeks' gestation. The TVS procedure consisted of two types of measurement: in the first, the probe was placed on the anterior fornix (standard technique) and in the second, the probe was inserted into the pessary to touch the anterior cervical lip (new technique). Two physicians consecutively performed these procedures and compared the measurements obtained. Intraclass correlation coefficients (ICCs) with 95% CI were used to evaluate interobserver reliability, and Bland-Altman analysis was used to assess interobserver agreement.

RESULTS

In total, 258 measurements (obtained from 43 women) were analyzed. Interobserver ICCs of the measurements obtained were 0.58 (95% CI, 0.34-0.75) for TPS, 0.65 (95% CI, 0.44-0.79) for the standard TVS technique and 0.97 (95% CI, 0.95-0.98) for the new TVS technique. Bland-Altman analysis showed small mean differences between measurements obtained by two physicians for the three methods, but with narrower limits of agreements (LOA) for the new TVS technique: TPS mean difference - 0.99 mm (95% LOA, - 13.23 to 11.25 mm), standard TVS technique mean difference - 0.23 mm (95% LOA, - 10.90 to 10.44 mm) and new TVS technique mean difference - 0.01 mm (95% LOA, - 2.57 to 2.55 mm). It was apparent from the images obtained that the external os was not visible in 89% of cases when either the TPS or standard TVS technique was used. However, the external os was visible in all cases when the new TVS method was used.

CONCLUSIONS

We propose a new technique for measuring and monitoring cervical length in women with a cervical pessary that provides improved visualization of the cervix and increased reliability in comparison to established techniques.