Mid-Trimester Cervical Consistency Index and Cervical Length to Predict Spontaneous Preterm Birth in a High-Risk Population

Assessment of novel sonographic and biochemical tools for spontaneous preterm birth prediction in asymptomatic twin pregnancies

INTRODUCTION

Prematurity is a major global health issue. Twin pregnancies are a group at especially high risk of preterm birth. Sonographic mid-trimester cervical length has limited accuracy in predicting preterm birth. This study aimed to evaluate the association between mid-trimester sonographic markers of early cervical remodeling and cervical inflammatory biomarkers and fetal fibronectin, alone or in combination, as predictors of preterm birth before 34+0 weeks in asymptomatic twin pregnancies.

MATERIAL AND METHODS

Prospective cohort study, including uncomplicated dichorionic or monochorionic-diamniotic twin pregnancies, recruited and assessed between 18+0 and 24+6 weeks, from a single tertiary referral center between 2020 and 2023. At inclusion, transvaginal ultrasound was performed to assess the following sonographic markers (cervical length, uterocervical angle, cervical consistency index, cervical texture) and an endocervical sample was obtained prior to ultrasound to quantify the following cervical inflammatory biomarkers (tumor necrosis factor alpha, interleukins 1b, 6, 8, 18, matrix metalloproteinase-8 and 9) and fetal fibronectin. The diagnostic performance of those sonographic and biochemical markers independently associated with spontaneous preterm birth before 34 weeks was analyzed by receiver operating characteristic curves and assessed through sensitivity and specificity analysis for several cutoffs.

RESULTS

Of the 172 women included, cervical length was shorter (36 mm vs. 40 mm; p = 0.025) and uterocervical angle was wider (137° vs. 120°; p = 0.004) in the preterm group. Cervical consistency index, cervical texture score, cervical inflammatory biomarkers, and fetal fibronectin were similar among the study groups. The area under the curve to predict spontaneous preterm birth before 34+0 weeks was 0.722 (95% CI 0.577 to 0.866) for cervical length, 0.789 (95% CI 0.683 to 0.895) for uterocervical angle, and 0.852 (95% CI 0.752 to 0.952) for a combination of both. Based on the receiver operating characteristics curve cutoff, sensitivity and specificity for cervical length ≤37 mm was 55.6% and 66.3%, for an uterocervical angle ≥135° was 77.8% and 76.1%, and for both criteria present 44.4% and 93.3%, respectively.

CONCLUSIONS

This finding of this study suggests that the combination of cervical length and uterocervical angle in mid-trimester sonographic assessment may improve the prediction of preterm birth before 34 weeks in asymptomatic and uncomplicated twin pregnancies.

The PRECISION study protocol: Can cervical stiffness in the second trimester predict preterm birth in high-risk singleton pregnancies? A feasibility, cohort study

BACKGROUND

Preterm birth (PTB) is a leading cause of neonatal morbidity and mortality. More than 13 million babies are affected globally every year and PTB will contribute to over 900,000 deaths. In the UK, PTB affects 8% of pregnancies and costs more than £260 million annually in neonatal care. Identifying those at risk of this devastating complication of pregnancy and implementing preventative treatment remains a maternal health priority. The mainstay of PTB prevention has been assessment of cervical length (CL) in women at high-risk of PTB. However, CL has limitations, namely it is invasive, user dependent and varies over time through pregnancy. Importantly, not all those who are high-risk with a short CL will subsequently deliver preterm and CL screening doesn't identify a sub-set of women who have a spontaneous PTB without a short cervix. Therefore, existing care pathways for managing PTB can potentially benefit from additional assessments of risk. Novel ways of assessing cervical structure and function may improve our ability to predict spontaneous PTB and refine preventative intervention. This feasibility study will explore the use of a new antenatal test of cervical stiffness for assessing risk of spontaneous PTB in a high-risk singleton population.

METHODS

PRECISION is a single site prospective, feasibility, cohort study of asymptomatic women with singleton pregnancies at high risk for spontaneous PTB attending an inner-city tertiary maternity hospital in the UK. All study participants will be undergoing routine screening and management of PTB as per local guidance (NICE/Saving Babies Lives guidance) including CL screening with transvaginal ultrasound. Cervical stiffness will be assessed using the Pregnolia System; a novel, licensed, CE-marked, aspiration-based device. A measurement is obtained by applying the device directly to the anterior lip of the cervix, visualised via placement of a speculum, and gives a quantitative assessment of cervical stiffness represented as the Cervical Stiffness Index (CSI, in mbar). Participants will undergo cervical stiffness assessments at up to three timepoints in the second trimester between 14+0 weeks and 25+6 weeks gestation. The cervical stiffness index data will be paired with routine PTB clinic CL measurements taken at the same time points. The primary outcome will focus on the feasibility of using this novel antenatal test in this high-risk population and explore any association between cervical stiffness and PTB.

DISCUSSION

This is an exploratory study to assess the use of this novel device in clinical practice. Direct comparison between cervical stiffness assessment using the Pregnolia System and CL assessment will determine the acceptability of this new assessment in this population, as well as explore its potential association with PTB. Our findings from this feasibility study will provide data on the potential of this novel device to impact PTB screening and evaluate acceptability of use in a high-risk population. Data on eligibility, recruitment rates and participant feedback will help inform future study design using the device.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05837390.

Performance of the First-Trimester Cervical Consistency Index to Predict Preterm Birth

Background/Objectives: Preterm birth (PTB) remains a significant global health challenge. Previous attempts to predict preterm birth in the first trimester using cervical length have been contradictory. The cervical consistency index (CCI) was introduced to quantify early cervical changes and has shown promise across various clinical scenarios in the mid-trimester, though testing in the first trimester is lacking. This study aims to assess the cervical consistency index performance in predicting preterm birth during the first trimester of pregnancy. Methods: In this prospective cohort study, focused exclusively on research, women with singleton pregnancies, both with and without a history of spontaneous preterm birth (sPTB), were included. The primary outcome was sPTB before 37 weeks, with a secondary outcome of sPTB before 34 weeks. CCI measurements were taken between 11+0 to 13+6 weeks of gestation. Receiver operating characteristic (ROC) curves were generated, and sensitivity and specificity were calculated for the optimal cut-off and for the 5th, 10th, and 15th percentile. Intraobserver and interobserver agreements were assessed using the intraclass correlation coefficient (ICC). Results: Among the 667 patients analyzed, the rates of sPTB before 37 and 34 weeks were 9.2% (61/667) and 1.8% (12/667), respectively. The detection rates (DRs) for CCI predicting PTB before 37 and 34 weeks were 19.7% (12/61) and 33.3% (4/12). Negative predictive values were 91.8% (546/595) and 98.7% (588/596), while the areas under the curve (AUC) for sPTB before 37 and 34 weeks were 0.62 (95% CI: 0.54-0.69) and 0.80 (95% CI: 0.71-0.89), respectively. Of the 61 patients with preterm birth, 13 (21.3%) had a preterm birth history; in this group, the CCI percentile 10th identified 39% (5/13). Intraobserver ICC was 0.862 (95% CI: 0.769-0.920), and interobserver ICC was 0.833 (95% CI: 0.722-0.902). Conclusions: This study suggests that utilizing CCI in the first trimester of pregnancy could serve as a valuable tool for predicting preterm birth before 34 weeks of gestation, demonstrating robust intraobserver and interobserver reliability.

Techniques for detecting cervical remodeling as a predictor for spontaneous preterm birth: current evidence and future research avenues in patients with multiple pregnancies

BACKGROUND

Spontaneous preterm birth occurs more frequently in multiple pregnancies. This syndrome has multiple triggers that result in a unified downstream pathway of cervical remodeling, uterine activity, and progressive cervical dilatation. Whilst the triggers for labor in multiple pregnancy may be different from singletons, the downstream changes will be the same. Identifying patients at risk of preterm birth is a priority as interventions to delay delivery and optimize the fetus can be initiated. Methods for screening for risk of preterm birth which focus on the detection of cervical remodeling may therefore have potential in this population.

METHODS

This review explores the evidence for the predictive utility for preterm birth of several published techniques that assess the physical, biomechanical, and optical properties of the cervix, with a focus on those which have been studied in multiple pregnancies and highlighting targets for future research in this population.

RESULTS

Fifteen techniques are discussed which assess the physical, biomechanical, and optical properties of the cervix in pregnancy. Of these, only three techniques that evaluated the predictive accuracy of a technique in patients with multiple pregnancies were identified: uterocervical angle, cervical consistency index, and cervical elastography. Of these, measurement of the uterocervical angle has the strongest evidence. Several techniques have shown predictive potential in singleton pregnancies, but have not yet been studied in multiple pregnancies, which would be a logical expansion of research.

CONCLUSION

Research on techniques with predictive utility for PTB in patients with multiple pregnancies is limited but should be a research priority. Overall, the theory supports the investigation of cervical remodeling as a predictor of PTB, and there are numerous techniques in development that may have potential in this field.

Comparison of Maternal-Fetal Outcomes among Unvaccinated and Vaccinated Pregnant Women with COVID-19

Background: This study sought to elucidate whether COVID-19 vaccination, during gestation or before conception, entails a decreased incidence of severe COVID-19 disease during pregnancy. Methods: This retrospective cohort study included all pregnant women that were followed up at a tertiary University Hospital with SARS-CoV-2 infection diagnosed between 1 March 2020 and 30 July 2022. The primary outcome of the study was to compare maternal and perinatal outcomes in unvaccinated and vaccinated pregnant patients with SARS-CoV-2 infection. Results: A total of 487 pregnant women with SARS-CoV-2 infection were included. SARS-CoV-2 infection during the third trimester of pregnancy was associated with an 89% lower probability of positive cord-blood SARS-CoV-2 IgG antibodies (OR 0.112; 95% CI 0.039-0.316), compared with infection during the first or the second trimester. Vaccinated pregnant women (201 (41.27%)) with COVID-19 had an 80% lower risk for developing pneumonia and requiring hospital admission due to COVID-19 than unvaccinated patients (aOR 0.209; 95% CI 0.044-0.985). Noticeably, pregnant patients with SARS-CoV-2 infection with at least two doses of the COVID-19 vaccine did not develop severe COVID-19. Conclusion: Vaccinated women with SARS-CoV-2 infection during pregnancy are associated with decreased hospital admission due to COVID-19 as well as reduced progression to severe COVID-19.

Prediction of Preterm Birth with Serial Measurements of Ultrasound Markers

To compare the ability of cervical length (CL), anterior cervical angle (ACA), and cervical consistency index (CCI) to predict premature birth.

METHODS

This prospective study involved 85 pregnant women who gave birth prematurely and a control group of 31 pregnant women who gave birth at term. The study was performed in the Obstetrics and Gynecology Clinic of the Municipal Clinical Hospital Filanthropia Craiova between January 1, 2019, and January 1, 2022. Cases were examined using transvaginal ultrasonography (TVU) in the second and third trimesters of pregnancy, and cervical length (CL), Anterior Cervical Angle (ACA), and Cervical Consistency Index (CCI) were measured.

RESULTS

The mean value from the three measurements at all three parameters was statistically significant with preterm birth (p<0.05). Cervical length <25mm, was highly significant in the prediction of preterm labor with a sensitivity of 99%, specificity of 61%, positive predictive value (PPV) of 78%, negative predictive value (NPV) of 97 %, and a positive likelihood ratio (LR+) of 2.54 and negative likelihood ratio (LR-) of 0.02. CCI also remains, despite low specificity and PPV values, a potential predictive parameter in the prediction of preterm birth, with a sensitivity of 73%, NPV of 92% and a LR+of 1.32 and LR- of 0.6 also correlated with CL, CCI being more difficult to interpret as an independent predictive parameter.

CONCLUSIONS

CL remains the standard parameter for predicting the preterm birth, but in combination with other parameters, the prediction rate can increase significantly.

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.

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.

Cervical modifications after pessary placement in singleton pregnancies with maternal short cervical length: 2D and 3D ultrasound evaluation

INTRODUCTION

The use of a pessary proved to prevent preterm birth in asymptomatic women with mid-trimester short cervical length (CL); however, the precise mechanisms by which the pessary confers its benefit remain unclear. The aim of this study was to evaluate multiple cervical characteristics assessed by 2-dimensional and 3-dimensional ultrasound before and after placement of a cervical pessary to ascertain its mechanism of action.

MATERIAL AND METHODS

In this prospective cohort study, we assessed the cervical characteristics in singleton pregnancies with maternal short CL and compared them with matched reference women with normal CL. The variables evaluated were: CL, uterocervical angles, cervical consistency indices (cervical consistency index and CL consistency index), cervical volume and vascular indices. All variables were re-assessed immediately after pessary placement and 4-6 weeks later in all participants. Mann-Whitney U test was used to assess differences between groups and paired samples t test for comparisons in two different examinations in the same women. The aim of this study was to evaluate multiple cervical ultrasound variables before and after the placement of a cervical pessary and compare the evolution of these variables with a reference group with normal CL to better understand the device's mechanism of action.

RESULTS

Thirty-three women with short CL and 24 reference women with normal CL were enrolled. At the time of enrollment, gestational age and maternal baseline characteristics did not differ between groups. Immediately after pessary placement, CL increased, uterocervical angles were narrower and cervical consistency increased significantly. When the magnitude of change in cervical variables was compared over time between the reference group and the study group, median CL had increased in the study group (1.47 mm) but it had shortened in the reference group (-2.56 mm). These inverse trends were statistically significant (P = 0.006).

CONCLUSIONS

Cervical pessary reduces both uterocervical angles and corrects cervical angulation by pushing the cervix up toward the uterus. Maintaining the cervix aligned to the uterine axis leads to reduced cervical tissue stretch, so avoiding further cervical shortening. All these changes were present after pessary placement; however, the clinical implications of these findings remain unknown.

The prediction of preterm delivery: What is new?

Preterm birth, defined as birth occurring prior to 37 weeks gestation, is a serious obstetric problem accounting for 11% of pregnancies worldwide. It is associated with significant neonatal morbidity and mortality. Predictive tests for preterm birth are incredibly important, given the huge personal, economic, and health impacts of preterm birth. They can provide reassurance for women who are unlikely to deliver early, but they are also important for highlighting those women at higher risk of premature delivery so that we can offer prophylactic interventions and help guide antenatal management decisions. Unfortunately, there is unlikely to be a single test for predicting preterm birth, but a combination of tests is likely to improve clinical prediction. This review explores the clinical utility of the currently marketed predictive tests for preterm birth in both singleton and multiple pregnancies, as well as discussing novel predictive tests that may be useful in the future.