Anterior cervical angle as a new biophysical ultrasound marker for prediction of spontaneous preterm birth

Value of post-cerclage transvaginal ultrasound in predicting preterm birth at <28 weeks in twin pregnancy with ultrasound-indicated cerclage

OBJECTIVE

To evaluate the value of transvaginal ultrasound parameters before and after cerclage in twins in predicting spontaneous preterm birth (sPTB) before 28+0 weeks.

METHODS

We retrospectively studied the medical records of twin-pregnant women who underwent ultrasound-indicated cerclage between January 2016 and February 2022 at our hospital. Recorded transvaginal ultrasound images before and after cerclage were reassessed for cervical length (CL), uterocervical angle (UCA), funneling, and sludge. Multivariate logistic and Cox regression analyses were performed to identify the independent risk factors associated with sPTB before 28 weeks.

RESULTS

A total of 69 women were included. Among them, 17 women (24.64%) delivered before 28 weeks of age. Regression analysis revealed a significant association of post-cerclage CL, UCA, white blood cell (WBC) count, and gestational age (GA) at cerclage with sPTB before 28 weeks. The area under the curve of these predictors was 0.938 (95% confidence interval, 0.882-0.994; p < .001), with a sensitivity of 88.2%, specificity of 92.3%, positive predictive value of 78.9%, and negative predictive value of 96.0%. Cox analysis showed that post-cerclage UCA was an independent risk factor affecting the cerclage-to-delivery interval (hazard ratios, 1.026; 95% confidence interval (CI), 1.004-1.048; p = .019).

CONCLUSIONS

The combination of post-cerclage CL, UCA, WBC count, and GA at cerclage showed good performance in predicting sPTB at <28 weeks in twin pregnancy. Post-cerclage UCA is also associated with pregnancy latency. We found that post-cerclage cervical ultrasound may be useful to predict preterm birth before 28 weeks in twins who undergo ultrasound-indicated cerclage.

Distribution of uterocervical angles of pregnant women at 16+ 0 to 23+ 6 weeks gestation with low risk for preterm birth: first vietnamese cohort of women with singleton pregnancies

BACKGROUND

Cervical length (CL) measured by ultrasound in the second trimester is a predictor of spontaneous preterm birth (sPTB). The uterocervical angle (UCA) has recently been suggested as a predictor to identify women at risk of sPTB. The aim of this study was to investigate the UCAs' distribution in singleton pregnant women at 16^+ 0 - 23^+ 6 weeks of gestation with low risk for sPTB.

METHODS

This was a prospective cohort study of 1,051 pregnant women with singleton pregnancies at low risk for preterm delivery. Pregnant women with a viable singleton fetus at 16^+ 0 - 23^+ 6 weeks of gestation were enrolled in the study conducted at the Haiphong Hospital of Obstetrics and Gynecology, Vietnam, from 09/2019 to 09/2020. CL and the UCA were assessed using transvaginal ultrasonography (TVS) by a single sonographer. Subjects were followed-up until the end of pregnancy, and maternal and neonatal outcomes were recorded. The UCAs' range and their relationship with gestational age were evaluated using regression analysis. P < 0.05 was considered statistically significant.

RESULTS

The normal range of the UCA (5^th - 95^th percentiles) was 46.47° (95% CI, 40.27°-51.81°) to 127.06° (95% CI, 123.02° - 130.71°). The UCAs in the preterm birth (< 37 weeks) and full-term groups were 117.86° ± 20.25° and 83.80° ± 24.18°, respectively (p < 0.001). Linear regression analysis showed a significant change in the UCA range from 16^+ 0 to 23^+ 6 weeks of gestation (2.51 degrees per week, p < 0.001). The linear function yielded the highest correlation coefficient in the variation rule of the UCA values (r = 0.22). A total of 42/63 (66.7%) patients with preterm birth < 37 weeks had a UCA above the 75^th percentile. The majority of women with preterm birth had a UCA ≥ 95° compared with those with full-term delivery (88.9% vs. 31.3%, p < 0.001).

CONCLUSIONS

The results of this study present background information about the normal range of UCA values in singleton pregnant women at 16^+ 0 to 23^+ 6 weeks at low risk for sPTB in this Vietnamese cohort. In this study population at low risk for sPTB, pregnant women with a UCA value ≥ 95^o were also considered at risk for preterm birth.

Prediction of preterm delivery in threatened preterm labour with short cervical length

In this study, we evaluated the value of the uterocervical angle (UCA), myometrial thickness (MT), sICAM-1, sVCAM-1, soluble E-selectin (sE-selectin) and pentraxin 3 (PTX3) levels in women with threatened preterm labour (TPL) in predicting spontaneous preterm birth (sPTB) within 14 days in symptomatic women with cervical length (CL) measurements between 10 and 25 mm. Forty-six patients diagnosed with TPL, 47 healthy pregnant women were evaluated in a case-control study. sE-selectin (AUC = 0.744, p = .007) and PTX3 (AUC = 0.711, p = .019) were found to be effective in predicting preterm delivery within 14 days. In conclusion, maternal sE-selectin and PTX3 levels may be helpful in identifying pregnancies that will deliver within 14 days in symptomatic women with CL measurements between 10 and 25 mm. However, maternal sICAM-1 and sVCAM-1 levels, MT and UCA are not effective in the prediction of sPTB in TPL pregnancies. Impact StatementWhat is already known on this subject? Aetiology of spontaneous preterm birth (sPTB) is unclear and believed to be multifactorial, infection, inflammation, vascular endothelial dysfunction and uteroplacental ischaemia are all considered to be related to preterm delivery syndrome. Transvaginal cervical length (CL) measurement is a good indicator of increased risk of sPTB. Inflammation is accepted to have a central role in the process of labour.What do the results of this study add? soluble E-selectin (sE-selectin) and pentraxin 3 (PTX3) levels may be helpful in identifying pregnancies that will deliver within 14 days in symptomatic women with CL measurements between 10 and 25 mm.What are the implications of these findings for clinical practice and/or further research? This study will help understand the important role of the inflammatory process in predicting spontaneous preterm birth.

Evaluation of Uterocervical Angle and Cervical Length as Predictors of Spontaneous Preterm Birth

Aim The aim of this article was to evaluate uterocervical angle (UCA) and cervical length (CL) measured at 16 to 24 weeks of gestation using transvaginal sonography (TVS) as predictors of spontaneous preterm birth.

Methods In this prospective study, TVS was performed in 159 primigravidas with a singleton, uncomplicated pregnancy at 16 to 24 weeks of gestation to measure the anterior UCA and CL. All the cases were followed until labor to document gestational age at delivery.

Results The risk of spontaneous preterm birth was higher in women with obtuse UCA (>95 degrees) with sensitivity of 86.7%, specificity of 93.0%, positive predictive value of 83.0%, negative predictive value of 94.6%, and p-value of <0.001. The difference between the means was statistically significant (p-value < 0.001). UCAs ≥105degrees and 95 to 105 degrees were found to be significantly associated with spontaneous preterm births at <34 weeks and 34 to 37 weeks, respectively. CL <2.5 cm was found to predict spontaneous preterm births at <37 weeks with sensitivity of 31.1%, specificity of 95.6%, and p-value of <0.001. UCA was found to be a better predictor of spontaneous preterm birth with a higher coefficient of variation (56.4%) when compared with CL (16.9%).

Conclusions UCA proved to be a novel ultrasound parameter that can serve as a better predictor of spontaneous preterm births in comparison to CL. A strong correlation exists between obtuse UCA and a risk of spontaneous preterm birth.

Measurement of the Uterocervical Angle for Predicting the Latent Period in Pregnancy Exhibiting Premature Membrane Rupture

OBJECTIVES

The duration of the latent period is uncertain in preterm premature rupture of membranes (PPROM). This time estimate provides information on the time of the corticosteroid to be applied and the time of delivery of the pregnant women. Here, we used transvaginal sonography to determine the relationship between the uterocervical angle (UCA) and PPROM latency and the risk for neonatal complications.

DESIGN

This is a prospective cohort study of 80 singleton pregnancies with PPROM. Participants/Materials, Setting, and Methods: This prospective cohort study was conducted at a tertiary center with a total of 80 singleton pregnancies with PPROM. The UCA and cervical length were measured in the first evaluation of PPROM in patients between 24 and 34 weeks of age. The study population was subdivided into 2 groups: group 1 (n = 27) included women who gave birth within 10 days after a PPROM diagnosis and group 2 (n = 53) included women who gave birth later than this. Our aim was latency prediction (more or less than 10 days) in PPROM patients undergoing regular UCA monitoring.

RESULTS

Of the women in group 1, 74.1% (n = 20) had spontaneous births and 7.4% (n = 2) had induced births because of clinical chorioamnionitis. Of the women in group 2, 71.6% (n = 38) had spontaneous births and 7.6% (n = 4) had induced births because of clinical chorioamnionitis (n = 3) or poor fetal condition (n = 1). We drew receiver operating characteristic curves to explore whether the UCA predicted birth within 10 days of PPROM. The area under the curve was 0.894 (p < 0.001). The optimal UCA cutoff was 108°, with 93% sensitivity and 85% specificity.

LIMITATIONS

First, the sample size was small; it would have been better to have more patients. Second, we measured the UCA only once. Third, patients were not categorized by parity.

CONCLUSIONS

The UCA, measured by the transvaginal route, can successfully predict latent period in PPROM. Measuring the UCA can be useful to determine the time of corticosteroid administration and to inform patients about the time of birth.

Uterocervical angle at 20 weeks: A promising predictor of spontaneous preterm birth in twin pregnancies

OBJECTIVE

To compare the performance of uterocervical angle (UCA) and cervical length (CL) measurement at 20 weeks of pregnancy for prediction of spontaneous preterm birth (sPTB) in twin pregnancies.

STUDY DESIGN

We conducted a retrospective cohort study of 424 twin pregnancies who delivered in our center from October 2014 to December 2018 and who underwent transvaginal ultrasound between 19⁺⁰-22⁺⁰ weeks to measure CL during routine second trimester scan. Recorded ultrasound images of CL were reassessed to evaluate UCA. Medical and obstetric data were also collected for statistical analysis.

RESULTS

A total of 424 women were included. The rates of sPTB rate below 28, 32 and 34 weeks of gestation were 2.8 %, 5.4 % and 10.4 %, respectively. ROC curves showed a better area under the curve (AUC) for UCA at all gestational ages compared with CL (AUC for sPTB <28 weeks 0.902 (p < 0.001) vs 0.620 (p 0.175); AUC for sPTB <32 weeks 0.740 (p 0.001) vs 0.620 (p 0.058); AUC for sPTB <34 weeks 0.676 (p 0.001) vs 0.632 (p 0.047). UCA > 120 degrees was significantly associated with sPTB <28 weeks (p < 0.001; OR 39.17; CI 4.81-319.23; NPV, 99.65 %), <32 weeks (OR 4.23; p 0.002) and <34 weeks of gestation (OR 2.66; p 0.01).

CONCLUSION

In our study, an UCA > 120 degrees allowed to identify those women with twin pregnancies at risk of sPTB and performed better than CL measurement.

Measurement of the uterocervical angle for the prediction of preterm birth in symptomatic women

Purpose

To examine if the uterocervical angle (UCA) can be used to predict preterm delivery in women with painful and regular uterine contractions and a cervical length of 25 mm or less.

Methods

Retrospective study at the perinatal unit of the University Hospital of Tuebingen, Germany. Women with singleton gestation and preterm contractions between 24 + 0 and 33 + 6 weeks’ gestation were included. For the UCA measurement, a line is placed from the internal os to the external os irrespective of whether the cervix is straight or curved. A second line is drawn to delineate the lower uterine segment. The angle between the two lines is the UCA measurement. The measurements were taken on stored images from our database.

Results

The study consisted of 213 singleton pregnancies. At the time of UCA measurement, median maternal and gestational age was 31.4 years and 29.7 weeks’ gestation. Median gestational age at delivery was 35.3 weeks and the corresponding birth weight 2480 g, respectively. The UCA measurement in women who delivered within 2 days, between 3–7 days and after 7 days was not helpful to distinguish between these three groups [median UCA measurements: 108.5°, 108.0° and 107.3° (Kruskal–Wallis test p = 0.576)]. Uni- and multivariate logistic multiple regression analysis demonstrated that the delivery within 2 days was only dependent on the gestational age and the cervical length at the time of presentation.

Conclusion

The measurement of UCA is not useful in predicting preterm birth in the subsequent 7 days after an episode of preterm contractions.

Machine Learning Methods for Preterm Birth Prediction: A Review

Preterm births affect around 15 million children a year worldwide. Current medical efforts focus on mitigating the effects of prematurity, not on preventing it. Diagnostic methods are based on parent traits and transvaginal ultrasound, during which the length of the cervix is examined. Approximately 30% of preterm births are not correctly predicted due to the complexity of this process and its subjective assessment. Based on recent research, there is hope that machine learning can be a helpful tool to support the diagnosis of preterm births. The objective of this study is to present various machine learning algorithms applied to preterm birth prediction. The wide spectrum of analysed data sets is the advantage of this survey. They range from electrohysterogram signals through electronic health records to transvaginal ultrasounds. Reviews of works on preterm birth already exist; however, this is the first review that includes works that are based on a transvaginal ultrasound examination. In this work, we present a critical appraisal of popular methods that have employed machine learning methods for preterm birth prediction. Moreover, we summarise the most common challenges incurred and discuss their possible application in the future.

Uterocervical Angle and Cervical Length as a Tool to Predict Preterm Birth in Threatened Preterm Labor

Objective

To evaluate the diagnostic performance of uterocervical angle (UCA) and UCA with cervical length (CL) in predicting preterm delivery in threatened preterm labor.

Methods

A multicenter prospective observational cohort study was conducted in 160 pregnant women having threatened preterm labor at Srinagarind and Udonthani Hospitals in Thailand between March 2019 and June 2020. Researchers measured UCA and CL by transvaginal ultrasonography. Medical records were reviewed for patient characteristics, and patients were followed up until the date of delivery to assess for the outcome of preterm birth. The cut-off point of UCA was determined from receiver operating characteristic curve analysis. The sensitivity, specificity, likelihood ratio, positive and negative predictive values (PPV and NPV) of UCA and of UCA with CL for predicting preterm birth were determined.

Results

The incidence of preterm birth in women having threatened preterm labor was 27%. The sensitivity, specificity, PPV and NPV of UCA ≥110.97 degrees for predicting preterm birth were 65.1%, 43.6%, 29.8% and 77.3%, respectively. The sensitivity, specificity, PPV and NPV of UCA ≥110.97 degrees with CL <3.4 centimeters for predicting preterm birth were 48.8%, 68.4%, 36.2% and 78.4%. The specificity and NPV of UCA with CL were higher than for UCA alone.

Conclusion

With adequate sensitivity and high NPV, UCA by TVS can be supplemented with CL measurement in threatened preterm labor management to increase the diagnostic performance for predicting preterm birth.

Uterocervical angle as a predictor of preterm birth on a high-risk collective between 20 and 31 weeks of gestation: A cohort analysis

INTRODUCTION

The cervical length (CL) measurement is a widely used method to estimate the risk of preterm birth. Due in particular to the high false-positive rate, the establishment of markers with improved test characteristics is a great challenge. A potential predictor of preterm birth is the uterocervical angle (UCA) and this additional measurement may improve the risk assessment. It was the aim of this study to compare the test properties of CL and UCA on patients at risk for preterm birth.

MATERIAL AND METHODS

109 patients with at least one of the following signs of threatening preterm birth between 20^+0/7 and 31^+6/7 weeks were included in a prospective cohort analysis: regular (>3/30 min) or painful uterine contractions, CL below 25 mm or a history of preterm birth. Exclusion criteria were premature rupture of membranes, hypertensive disorders, vaginal bleeding, surgical cerclage, Arabin pessary or cervical dilation of more than 30 mm. The determination of the UCA was carried out in a standardized manner using the image documents captured by vaginal sonographic CL measurement. The primary endpoint was preterm birth <34 weeks, secondary endpoints were delivery <37 weeks and within 7 days.

RESULTS

The UCA was on average 103° and the mean UCA in preterm and term groups did not differ significantly (P = .924). The UCA was not predictive for threatened preterm birth, even if only singletons were considered. For CL the best predictive accuracy for preterm birth <34 weeks was observed at a cut-off value of 14 mm with sensitivity 0.50, specificity 0.80, positive predictive value 0.30, negative predictive value 0.90, positive likelihood ratio 2.4, negative likelihood ratio 0.6 and an odds ratio of 3.9 (95% confidence interval 1.3-11.7, P = .016).

CONCLUSIONS

The assessment of UCA in patients at risk for preterm birth was not suitable to predict the probability of a threatened preterm birth. Measurement of UCA cannot be recommended in this situation.

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.

The Predictive Value of the Cervical Consistency Index to Predict Spontaneous Preterm Birth in Asymptomatic Twin Pregnancies at the Second-Trimester Ultrasound Scan: A Prospective Cohort Study

Novel transvaginal ultrasound (TVU) markers have been proposed to improve spontaneous preterm birth (sPTB) prediction. Preliminary results of the cervical consistency index (CCI), uterocervical angle (UCA), and cervical texture (CTx) have been promising in singletons. However, in twin pregnancies, the results have been inconsistent. In this prospective cohort study of asymptomatic twin pregnancies assessed between 18⁺⁰–22⁺⁰ weeks, we evaluated TVU derived cervical length (CL), CCI, UCA, and the CTx to predict sPTB < 34⁺⁰ weeks. All iatrogenic PTB were excluded. In the final cohort of 63 pregnancies, the sPTB rate < 34⁺⁰ was 16.3%. The CCI, UCA, and CTx, including the CL was significantly different in the sPTB < 34⁺⁰ weeks group. The best area under the receiver operating characteristic curve (AUC) for sPTB < 34⁺⁰ weeks was achieved by the CCI 0.82 (95%CI, 0.72–0.93), followed by the UCA with AUC 0.72 (95%CI, 0.57–0.87). A logistic regression model incorporating parity, chorionicity, CCI, and UCA resulted in an AUC of 0.91 with a sensitivity of 55.3% and specificity of 88.1% for predicting sPTB < 34⁺⁰. The CCI performed better than other TVU markers to predict sPTB < 34⁺⁰ in twin gestations, and the best diagnostic accuracy was achieved by a combination of parity, chorionicity, CCI, and UCA.

Prospective evaluation of the uterocervical angle as a predictor of spontaneous preterm birth

INTRODUCTION

The uterocervical angle has been proposed as an ultrasound marker to predict spontaneous preterm birth; however, the studies that provided this evidence were retrospective and their results heterogeneous. This study aimed to assess the ability of the uterocervical angle to predict spontaneous preterm birth before 34 and 37 weeks of gestation.

MATERIAL AND METHODS

A prospective cohort study with singleton pregnancies between 19.0 and 22.6 weeks of gestation. Uterocervical angle and cervical length were measured by transvaginal ultrasound. Maternal history and pregnancy data were recorded. Delivery data were subsequently collected.

RESULTS

The final analysis included 1453 singleton pregnancies. Spontaneous preterm birth before 37 weeks occurred in 52 cases (3.6%) and before 34 weeks in 17 (1.2%). For the prediction of spontaneous preterm birth before 34 weeks, the area under the curve for the uterocervical angle was 0.67 (95% CI 0.54-0.79) and the detection rates were 5.9% and 23.5% for fixed false-positive rates of 5% and 10%, respectively. For the prediction of spontaneous preterm birth before 37 weeks, the area under the curve was 0.58 (95% CI 0.50-0.67) and the detection rates were 5.8% and 18% for fixed false-positive rates of 5% and 10%, respectively. Combined predictive models were studied. To predict spontaneous preterm birth before 34 weeks, the best model was provided by a combination of uterocervical angle and cervical length (area under the curve 0.72; 95% CI 0.58-0.86). The detection rates of this model were 35.3% and 41.2% for fixed false-positive rates of 5% and 10%, respectively. To predict spontaneous preterm birth before 37 weeks of gestation, the best model was provided by a combination of uterocervical angle, cervical length, and previous history of spontaneous preterm birth (area under the curve 0.64; 95% CI 0.55-0.72). The detection rates of this model were 15.4% and 30.8% for fixed false-positive rates of 5% and 10%, respectively. Obese women and those with a history of cesarean section had a wider uterocervical angle.

CONCLUSIONS

The uterocervical angle, measured mid-trimester, is a poor predictor of spontaneous preterm birth.

Uterocervical angle as a predictor of spontaneous preterm birth in twin pregnancies

Objective: To assess the ability of uterocervical angle (UCA) compared with cervical length (CL) to predict the risk of spontaneous preterm birth (sPTB) in twin pregnancies and its performance when it was included in a combined predictive model of clinical and ultrasonographic parameters.Methods: We conducted a retrospective cohort study of twin pregnancies undergoing transvaginal ultrasound between 19⁺⁰-21⁺⁶ weeks to measure CL during routine second trimester scan from January 2015 through December 2016. Recorded ultrasound images of CL were reassessed to evaluate UCA. Medical and obstetric data were also collected for statistical analysis. A logistic regression model was created for predicting sPTB including UCA and other variables.Results: A total of 177 women were included. The rates of sPTB rate below 28, 32 and 34 weeks of gestation were 4.5%, 6.8% and 12.4%, respectively. ROC curves showed a better area under the curve (AUC) for UCA at all gestational ages compared with CL (AUC for sPTB <28 weeks 0.840 (p = .005) vs 0.627 (p = .388); AUC for sPTB <32 weeks 0.706 (p = .022) vs 0.619 (p = .255); AUC for sPTB <34 weeks 0.674 (p = .008) vs 0.568 (p = .344). UCA >117 degrees was significantly associated with sPTB <28 weeks (p = .002; OR 15.3; CI 1.66-142.37; NPV, 99.2%), <32 weeks (OR 3.84; p = .031) and <34 weeks of gestation (OR 3.10; p = .016). Based on multivariate analyses, the best predictive model included uterocervical angle (p = .032), cervical length (p = .002) and maternal height (p = .001) (Nagelkerke R² 0.944).Conclusion: In our study, an UCA > 117 degrees allowed to identify those women with twin pregnancies at risk of sPTB and performed better than CL measurement. Our combined prediction model was able to adequately predict the risk of sPTB in the twin pregnancies of our research.

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.

The role of noninvasive diagnostic imaging in monitoring pregnancy and detecting patients at risk for preterm birth: a review of quantitative approaches

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. The ability to predict patients at risk for preterm birth remains a major health challenge. The currently available clinical diagnostics such as cervical length and fetal fibronectin may detect only up to 30% of patients who eventually experience a spontaneous preterm birth. This paper reviews ongoing efforts to improve the ability to conduct a risk assessment for preterm birth. In particular, this work focuses on quantitative methods of imaging using ultrasound-based techniques, magnetic resonance imaging, and optical imaging modalities. While ultrasound imaging is the major modality for preterm birth risk assessment, a summary of efforts to adopt other imaging modalities is also discussed to identify the technical and diagnostic limits associated with adopting them in clinical settings. We conclude the review by proposing a new approach using combined photoacoustic, ultrasound, and elastography as a potential means to better assess cervical tissue remodeling, and thus improve the detection of patients at-risk of PTB.

Prediction of preterm birth and adverse perinatal outcomes after cervical pessary placement in singleton pregnancies with short cervical length

OBJECTIVES

To identify ultrasound-assessed cervical characteristics, modified after pessary placement, which could be predictive of spontaneous preterm birth (sPTB) at < 34 weeks of gestation (WG) or severe adverse perinatal outcomes (APO).

STUDY DESIGN

This prospective observational study conducted at Vall d'Hebron Universitary Hospital assessed multiple cervical characteristics in women with short cervical length (CL). All participants were examined by transvaginal ultrasound before and immediately after a cervical pessary was placed. Cervical assessment included CL, uterocervical angles (UCA), and cervical consistency indexes (cervical consistency index (CCI) and cervical length consistency index (CLCI)). Pregnancy outcomes were recorded to determine the capacity of these variables for predicting sPTB at < 34 WG and severe APO.

RESULTS

Thirty-one women with short CL, 17 (54.8%) with asymptomatic midtrimester short CL, and 14 (45.2%) after arrested threatened preterm labor were enrolled. After pessary placement, transvaginal ultrasound detected four participants in whom the pessary was not correctly placed around the cervix (12.9%); additionally, significant changes were observed in most cervical baseline characteristics, with CL, anterior UCA (A-UCA), CLCI, and intersegmentary angle (ISA) being predictive of sPTB at <34 WG and severe APO. Receiver operator curves were calculated to compare the predictive capacity of these variables, with CL and A-UCA after pessary placement being the best predictive parameters with an area under the curve of 0.88 and 0.87, respectively.

CONCLUSIONS

Transvaginal ultrasound after pessary placement detects incorrect pessary placement after pessary insertion and during follow-up. APO and sPTB can be predicted by measuring CL, A-UCA, CLCI, and ISA immediately after pessary placement, being CL and A-UCA more accurate and easier to be measured. Our results help to better identify women in whom the pessary is more likely to fail. Further research is required to assess the effectiveness of applying alternative, sequential or additional treatments to reduce prematurity and our results could be considered when designing such studies.

Correlation of transabdominal and transvaginal sonography for the assessment of uterocervical angle at 16-24 weeks' gestation

The objective of this study was to determine the correlation between transabdominal (TAS) and transvaginal sonography (TVS) uterocervical angle (UCA) measurement in pregnant women with no history of previous preterm birth. A cross-sectional study involving singleton pregnancies between 16 and 24 weeks of gestation who underwent routine foetal anatomical scan was conducted. The TAS-UCA measurement was performed before voiding and with an empty bladder. A total of 256 women completed the sonography. The mean maternal age was 32 ± 6.68 years. The mean gestation age at the time of ultrasound assessment was 19 ± 1.71 weeks. The mean prevoid TAS-UCA was 119.74 ± 33.12° and the mean postvoid TAS-UCA was 110.73 ± 25.30°. There was a significant difference between prevoid and postvoid TAS-UCA measurement (p < .05). The mean TVS-UCA was 103.91 ± 26.42°. The Pearson correlation coefficients of prevoid and postvoid TAS-UCA with TVS-UCA were 0.438 and 0.601, respectively. In conclusion, the postvoid TAS-UCA has moderate correlation with TVS-UCA measurement and is better than the prevoid TAS-UCA in women with low risk for preterm birth.IMPACT STATEMENTWhat is already known on this subject? TVS is the gold standard for cervical length (CL) assessment for prediction preterm birth. However, TVS requires an experienced or trained sonographer and some women decline TVS because of the embarrassment and discomfort during examination. Several studies have demonstrated the correlation between TAS and TVS and suggested that TAS could be an alternative for CL screening. UCA has been reported as a new predictor of spontaneous preterm birth and is usually performed by TVS. Thus, it is interesting to evaluate whether TAS can be a substitute procedure for TVS in UCA measurement.What the results of this study add? TAS may be used as a substitute procedure for TVS and the postvoid TAS is more appropriate than prevoid TAS for UCA measurement.What the implications are of these findings for clinical practice and/or further research? TAS may be an alternative method for UCA measurement when TVS is unavailable or in pregnant women who decline TVS-UCA measurement. However, further study should be conducted to confirm the association between TVS-UCA and postvoid TAS-UCA before deciding to use postvoid TAS-UCA as a screening tool for preterm prediction.

Second trimester uterocervical angle and spontaneous preterm birth in twins

Objective: To determine if there is an association between uterocervical angle (UCA) and spontaneous preterm birth (sPTB) < 37 weeks for women with twins.Materials and methods: Retrospective cohort study from 2014 to 2017 of twin pregnancies with cervical length (CL) screening between 15 0/7 and 24 6/7 weeks. Monochorionic-monoamniotic twins were excluded. Post-hoc UCA measurements were analyzed as a continuous variable and a wide UCA was also defined as an angle >95° and >110°. The primary outcome was sPTB < 37 weeks. Secondary outcomes were sPTB <34 weeks, <32 weeks, CL, and performance metrics for UCA. Binary logistic regression controlled for age, tobacco use, prior sPTB, CL, and gestational age at CL measurement.Results: A total of 114 women were studied. The rate of sPTB <37 weeks was 35.0%, <34 weeks was 21.4%, and <32 weeks was 17.1%. As a continuous variable, mean UCA was 117.9° (SD 27.1°) for delivery ≥37 weeks and 133.1° (SD 23.1°) <37 weeks (p = .002). A wider mean UCA was also associated with sPTB <34 weeks (sPTB ≥34 weeks: 120.9° [SD 26.5°] vs. <34 weeks: 133.0° [SD 22.8°], p = .025) and sPTB <32 weeks (sPTB ≥32 weeks: 121.2° [SD 25.9°] vs. <32 weeks: 135.0° [SD 24.0°], p = .018). However, after controlling for age, prior sPTB, tobacco use, CL measurement, and gestational age at CL measurement, UCA was not associated with sPTB <37 weeks, <34 weeks, or <32 weeks. UCA >110° was associated with sPTB <37 weeks after controlling for confounders (aOR 3.6 [95% CI 1.2-10.5], p = 0.02). There was no association between UCA >110° and sPTB <34 or <32 weeks. Furthermore, a UCA >95° was not associated with sPTB <37, <34, or <32 weeks. As a screening tool for sPTB <37 weeks, a UCA of >110° had a sensitivity of 85.7%, specificity of 43.1%, positive predictive value of 53.2%, negative predictive value of 80.0%, positive likelihood ratio of 1.5, and negative likelihood ratio of 0.3.Conclusions: In a cohort of dichorionic-diamniotic and monochroionic-diamniotic twins, UCA >110° was associated with sPTB <37 weeks. However, second trimester UCA had a low positive likelihood ratio and was not a robust marker for the prediction of sPTB in twins.

Uterocervical angle: an ultrasound screening tool to predict satisfactory response to labor induction

Background: A wide uterocervical angle >95° detected during the second trimester was associated with an increased risk for spontaneous preterm birth.Objective: We aimed to determine whether an ultrasonographic marker, uterocervical angle, correlates with satisfactory response to labor induction.Study design: We conducted a prospective cohort study from May 2016 through December 2017 of singleton term gestations undergoing transvaginal ultrasound for cervical length screening and uterocervical angle measurement. Uterocervical angle was measured between the lower uterine segment and the cervical canal. Latent phase duration >720 min was accepted to be a prolonged latent phase. The primary outcome was a prediction of satisfactory response to labor induction (latent phase duration <720 min).Results: Both anterior uterocervical angle (AUC = 0.802, p < .001) and the cervical length (AUC = 0.679, p < .05) significantly predicted satisfactory response to labor induction. Optimal cutoff value was obtained at the value of 97° (64% sensitivity, 91% specificity) for anterior uterocervical angle and 27 mm (64% sensitivity, 64% specificity) for the cervical length. Kaplan-Meier survival analysis showed that duration from labor induction to delivery was significantly higher in a group with longer cervical length (p = .04), additionally labor induction to delivery time was significantly higher in a group with lower UCA (p = .04).Conclusions: Both the cervical length and anterior uterocervical length were predictors for the satisfactory response to labor induction, and both parameters were found to be significantly associated with time from induction to delivery in survival analysis.

Comparison of reliability between uterocervical angle and cervical length measurements by various experienced operators using transvaginal ultrasound

Purpose: To compare the reliability between uterocervical angle (UCA) and cervical length (CL) measurements by various experienced operators.Methods: Transvaginal ultrasonographies (TVS) were performed in 102 pregnant women between 16°^/7-24°^/7 gestational weeks by different levels of experienced operators. For both CL and UCA measurements, intraobserver variability was assessed for each operator by examining the range between maximum and minimum measurements in each participant, compared to the mean of all three measurements. Interobserver variabilities were explored using Bland-Altman analysis. Intraclass correlation coefficients were used for both intraobserver and interobserver reliability.Results: For intraobserver variability of the UCA, the ranges between maximum and minimum UCA measurements in operator 1 and 3 were 1.5º-34º and 2º-36º (n = 51), and in operators 2 and 3 were 0º-61º and 1º-25º (n = 51). Intraclass correlation coefficients (ICC) for intraobserver reliability were 0.90 for operator 1, 0.67 for operator 2 and 0.93 for operator 3. For interobserver variability of the UCA, the limits of agreement for mean UCA were -37.53º-38.41º and -36.27º-26.17º, and for maximum UCA were -39.47º-41.38º and -44.24º-22.9º in comparisons between operators 1 and 3, and operator 2 and 3, respectively. Intraclass correlation coefficients for mean UCA were 0.73 and 0.74, and for maximum UCA were 0.71 and 0.67 in comparisons between operators 1 and 3, and operator 2 and 3, respectively.Conclusions: The UCA measurements had a higher intra- and interobserver reliabilities than the CL measurements.

Can uterocervical angles successfully predict induction of labor in nulliparous women?

PURPOSE

Induction of labor is a common practice in obstetrics. In recent years, a newer ultrasonographic parameter called the uterocervical angle (UCA) has been identified as a predictive tool for births. Our purpose is to investigate the role of UCA in predicting successful induction of labor.

METHODS

The nulliparous term pregnancies (n:150) were grouped into successful/failed inductions of labor based on their progress into the active phase of labor after the administration of prostaglandin E2 (dinoprostone). The pre-induction cervical length (CL) and UCA were compared in the two groups. The study population was further grouped according to their modes of delivery and pre-induction UCAs were compared among the subgroups.

RESULTS

The mean UCAs were not significant among the successful induction and failed induction groups (105.46 ± 20.54 degrees in the successful group and 110.57 ± 13.46 degrees in the failed group). However, UCAs significantly varied among the modes of delivery subgroups. The median UCA was significantly higher in patients who delivered vaginally after a successful induction of labor than in patients who delivered via cesarean section. The median UCA value was lowest in patients who had a successful induction of labor but ended up having a cesarean section (Fig. 2). Further, the duration of the active phase of labor negatively correlated with the UCA but not the CL (rho=-0.23, p = 0.02). There was also a negative correlation between the CL and the UCA in patients who delivered vaginally after successful induction of labor (rho= -0.21, p = 0.03).

CONCLUSION

The UCA is a promising ultrasonographic marker in obstetrics. Although the pre-induction UCA did not predict the outcome of labor induction, patients with broader pre-induction UCAs were prone to have a shorter duration of active phase. The pre-induction CL and UCA are inversely corraleted in nulliparous women who delivered vaginally after a successful induction of labor.

The predictive nature of uterocervical angles in the termination of second trimester pregnancy

AIM

To establish how useful and the predictive capacity of uterocervical angles (UCA) in the termination of second trimester pregnancies.

MATERIAL AND METHODS

This prospective cohort study was conducted at a tertiary center with a total of 120 singleton pregnancies delivered between 14 and 24 gestational weeks. Before the beginning of misoprostol induction, patients were screened for both cervical length (CL) and uterocervical angles (UCA). The UCA is defined as an angle constructed by the measurement of the cervical canal and lower uterine segment. The study population was subdivided into four groups; successful and failed terminations at the end of 24 hours of induction and successful and failed terminations at the end of 48 hours of induction. We decided to further evaluate our study population based on their UCAs, and placed them into four categories; UCA ≥95°, UCA <95°, UCA ≥105°, and UCA <105°.

RESULTS

In the 24-hour time frame group, the mean UCA was 105.50 ± 15.38 degrees in the successful termination group and was 100.22 ± 11.12 degrees in the failed group (p = .001). In the 48-hour time frame group, the mean UCA was 104.19 ± 13.51° in the successful termination group and was 93.52 ± 7.84° in the failed group (p = .007). The mean hour of induction was shortest in the UCA ≥105° group.

CONCLUSIONS

Regardless of the time frames, patients who had successful terminations had a broader angle, less amount of misoprostol use and shorter duration of induction as compared to the failed termination groups. What do the results of this study add? The uterocervical angle has never been measured in second trimester pregnancies to predict the timing of termination. Our study demonstrated the useful application of this ultrasonographic finding in the prediction of successful second trimester terminations.

Anterior uterocervical angle measurement improves prediction of cerclage failure

OBJECTIVE

To compare the anterior uterocervical angle and cervical length as predictors of spontaneous preterm delivery in patients with transvaginal cerclage.

STUDY DESIGN

We retrospectively evaluated a cohort of 142 pregnant women with transvaginal cerclage placed over a 5-year period (2010 to 2015) were evaluated. Cervical morphology characteristics were measured from endovaginal imaging, including cervical length, cerclage height, funnel volume and anterior uterocervical angle prior to cerclage placement (UCA 1), shortly after cerclage placement (UCA 2) and the last image prior to delivery (UCA 3). Cerclage failure was defined as delivery prior to 36 weeks. Univariate analysis, receiver operator characteristic curves and binary logistic regression were used for statistical analysis. Statistical significance was defined as a P<0.05.

RESULTS

Among the 142 women with a transvaginal cerclage, 38% had cerclage failure. The mean gestational age at birth was 29.3±5.2 weeks in the failure group compared with 37.9±2.8 weeks in those that did not fail (P<0.001). Univariate analysis identified cervical length (P=0.034) and UCA 3 (P<0.001) as significantly associated with gestational age at birth. Receiver operator characteristic curves demonstrated improved prediction of delivery prior to 34 weeks at UCA 3=108^o (97% sensitivity, 65% specificity) compared to a cervical length of 25 mm. At <28 weeks, optimal performance of UCA 3 was found at 112^o (100% sensitivity, 62% specificity) compared with cervical length of 25 mm (29% sensitivity, 39% specificity). Binary logistic regression revealed UCA 3>108^o conferred an OR 35.1 (95% CI 7.7 to 160.3) for delivery prior to 34 weeks, and UCA 3>112^o an OR 42.0 (95% CI 5.3 to 332.1) for delivery prior to 28 weeks. In comparison, CL<25 mm had an OR 4.7 (95% CI 1.8 to 12.2) for delivery prior to 34 weeks and OR 6.0 (95% CI 1.9 to 19.3) prior to 28 weeks.

CONCLUSIONS

In patients with transvaginal cerclage, an increasingly obtuse anterior uterocervical angle reflects an increased risk of cerclage failure in the mid-trimester. Utilization of UCA measurement as a surveillance tool may improve identification of patients at risk for cerclage failure.

Uterocervical angle: a novel ultrasound screening tool to predict spontaneous preterm birth

BACKGROUND

Mechanical alteration of the cervical angle has been proposed to reduce spontaneous preterm birth. Performance of the uterocervical angle as measured by ultrasound for predicting spontaneous preterm birth is poorly understood.

OBJECTIVE

We sought to determine whether a novel ultrasonographic marker, uterocervical angle, correlates with risk of spontaneous preterm birth in a general population.

STUDY DESIGN

We conducted a retrospective cohort study from May 2014 through May 2015 of singleton gestations between 16 0/7-23 6/7 weeks undergoing transvaginal ultrasound for cervical length screening. Images were remeasured for uterocervical angle between the lower uterine segment and the cervical canal. Primary outcome was prediction of spontaneous preterm birth <34 weeks and <37 weeks by uterocervical angle and secondary outcome evaluated cervical length and spontaneous preterm birth.

RESULTS

A total of 972 women were studied. The rate of spontaneous preterm birth in this cohort was 9.6% for delivery <37 weeks and 4.5% for <34 weeks. Uterocervical angle of ≥95 degrees was significantly associated with spontaneous preterm birth <37 weeks with sensitivity of 80% (P < .001; confidence interval, 0.70-0.81; negative predictive value, 95%). Uterocervical angle of ≥105 degrees predicted spontaneous preterm birth <34 weeks with sensitivity of 81% (P < .001; confidence interval, 0.72-0.86; negative predictive value, 99%). Cervical length ≤25 mm significantly predicted spontaneous preterm birth <37 weeks (P < .001; sensitivity, 62%; negative predictive value, 95%) and <34 weeks (P < .001; sensitivity, 63%; negative predictive value, 97%). Regression analysis revealed a significant association of maternal age, nulliparity, race, and obesity at conception with spontaneous preterm birth and uterocervical angle. There was no correlation identified between history of dilation and curettage, abnormal Pap smear results, excisional cervical procedures, smoking, or obesity at delivery on spontaneous preterm birth and uterocervical angle.

CONCLUSION

A wide uterocervical angle ≥95 and ≥105 degrees detected during the second trimester was associated with an increased risk for spontaneous preterm birth <37 and <34 weeks, respectively. Uterocervical angle performed better than cervical length in this cohort. Our data indicate that uterocervical angle is a useful, novel transvaginal ultrasonographic marker that may be used as a screening tool for spontaneous preterm birth.