Ultrasound assessment of the cervix

Diabetes Mellitus as a Risk Factor for Spontaneous Preterm Birth in Women with a Short Cervix after Ultrasound-Indicated Cerclage

Background: Preterm birth (PTB) is a significant challenge in contemporary obstetrics, affecting over one in ten infants worldwide and accounting for 75% of perinatal mortality. Short cervical length during mid-trimester is well known to be associated with an increased risk of spontaneous preterm birth (sPTB). Ultrasound-indicated cerclage (UIC) is recommended to prevent sPTB in women with a short cervix at mid-trimester and a history of sPTB. Objectives: This retrospective observational study aimed to examine the impact of diabetes and obesity on the occurrence of sPTB in women who underwent UIC due to mid-trimester cervical shortening. Methods/Results: The analysis revealed that cervical length at the time of operation, preoperative erythrocyte sedimentation rate levels, and diabetes were independent risk factors for sPTB. Additionally, the presence of diabetes, particularly when combined with obesity, significantly elevated the risk of sPTB. Women with pregestational diabetes or those requiring insulin treatment had a higher propensity for preterm delivery compared to those with gestational diabetes managed through diet control alone. Conclusions: These findings emphasize the importance of considering maternal metabolic factors, such as diabetes and obesity, in women with a short cervix when planning for UIC and highlight the crucial role of optimizing maternal glucose control and weight management in reducing the risk of sPTB.

Cost-effectiveness of universal routine sonographic cervical-length measurement at 19 to 25 weeks' gestation

BACKGROUND

National second-trimester scanning of cervical length was introduced in Israel in 2010, and in the decade thereafter, a significant systematic reduction in preterm birth and in the delivery of low birthweight babies was found among singletons.

OBJECTIVE

In this study, we sought to estimate the cost-effectiveness of a national policy mandating second-trimester cervical length screening by ultrasound, followed by vaginal progesterone treatment for short cervical length in comparison with no screening strategy.

STUDY DESIGN

We constructed a decision model comparing 2 strategies, namely (1) universal cervical length screening, and (2) no screening strategy. This study used the national delivery registry of Israel's Ministry of Health. All women diagnosed with a second-trimester cervical length <25 mm were treated with vaginal progesterone and were monitored with a bimonthly ultrasound scan for cervical dynamics and threat of early delivery. Preterm birth prevalence associated with short cervical length, the efficacy of progesterone in preterm birth prevention, and the accuracy of cervical length measurements were derived from previous studies. The cost of progesterone and bimonthly sonographic surveillance, low birthweight delivery, newborn admission to intensive care units, the first-year costs of managing preterm birth and low birthweight, and instances of handicaps and the cost of their follow-up were extracted from the publicly posted registry of Israel's Ministry of Health and Israel Social Securities data. Monte Carlo simulations decision tree mode, Tornado diagrams, and 1- and 2-way sensitivity analyses were implemented and the base case and sensitivity to parameters that were predicted to influence cost-effectiveness were calculated.

RESULTS

Without cervical length screening, the discounted quality-adjusted life years were 30.179, and with universal cervical length screening, it increased to 30.198 (difference of 0.018 quality-adjusted life years). The average cost of no screening for cervical length strategy was $1047, and for universal cervical length screening, it was reduced to $998. The calculated incremental cost-effectiveness ratio was -$2676 per quality-adjusted life year (dividing the difference in costs by the difference in quality-adjusted life years). Monte Carlo simulation of cervical length screening of 170,000 singleton newborns (rounded large number close to the number of singleton newborns in Israel) showed that 95.17% of all babies were delivered at gestational week ≥37 in comparison with 94.46% of babies with the no screening strategy. Given 170,000 singleton births, the national savings of screening for short cervical length when compared with no cervical length screening amounted to $8.31M annually, equating to $48.84 for a base case, and the incremental cost-effectiveness ratio for each case of low birthweight or very low birthweight avoided was -$14,718. A cervical length <25 mm was measured for 30,090 women, and of those, 24,650 were false positives. The major parameters that affected the incremental cost-effectiveness ratio were the incidence of preterm birth, the specificity of cervical length measurements, and the efficacy of progesterone treatment. At a preterm birth incidence of <3%, universal screening does not lead to a cost saving.

CONCLUSION

National universal cervical length screening should be incorporated into the routine anomaly scan in the second trimester, because it leads to a drop in the incidence of preterm birth and low birthweight babies in singleton pregnancies, thereby saving costs related to the newborn and gaining quality-adjusted life years.

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.

A cross-sectional survey of women's views and preferences for preterm birth screening and treatment

OBJECTIVES

Primary outcomes were to determine; 1) the desire for more patient information from healthcare professionals on preterm birth (PTB) prevention 2) the desire for PTB screening surveillance or participation in research or 3) the acceptability of transvaginal ultrasound (TVUS) or vaginal examinations to predict spontaneous PTB.

METHODS

A 19-question, piloted, self-administered survey was completed by unselected pregnant women in a tertiary maternity hospital in Dublin, Ireland. Data was collected to include maternal socio-demographics, past obstetric history, and current pregnancy details, in addition to views and preferences on PTB screening and preventative treatments. Statistical analysis to include binary and multinomial regression was performed by IBM SPSS Statistics for Windows (Version 29.0).

RESULTS

277 women completed the study survey. 9.4% of women had attended the preterm birth surveillance clinic (PSC). 75.1% of respondents indicated a preference for more information from healthcare professionals about PTB. 65% reported that TVUS and vaginal examinations were acceptable in pregnancy. The acceptability of antenatal examinations was significantly influenced by ethnicity; white European (OR 2.58, CI 1.12-5.95, p = 0.003) and Asian (OR 3.39, CI 1.18-9.67, p = 0.02). Discomfort (25.3%) and vaginal bleeding (11.9%) were the most frequently reported concerns about TVUS. 95.7% of unselected women indicated that they would accept treatment to prevent PTB. Vaginal progesterone (53.8%) was preferred treatment compared to cervical cerclage (15.9%) or cervical pessary (16.6%). 55.6% of respondents stated they attend or wish to attend for additional appointments or research opportunities for PTB screening. Women with a previous PTB or second trimester miscarriage were more likely to attend or wish to attend for PTB screening (OR 3.23, CI 1.34-7.79, p = 0.009).

CONCLUSION

PTB is an important healthcare priority for pregnant women in Ireland. However, women require more information, counselling and reassurance about the utility and safety of TVUS in PSCs.

Searching and visualizing genetic associations of pregnancy traits by using GnuMoM2b

Adverse pregnancy outcomes (APOs) are major risk factors for women's health during pregnancy and even in the years after pregnancy. Due to the heterogeneity of APOs, only few genetic associations have been identified. In this report, we conducted genome-wide association studies (GWASs) of 479 traits that are possibly related to APOs using a large and racially diverse study, Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b). To display extensive results, we developed a web-based tool GnuMoM2b (https://gnumom2b.cumcobgyn.org/) for searching, visualizing, and sharing results from a GWAS of 479 pregnancy traits as well as phenome-wide association studies of more than 17 million single nucleotide polymorphisms. The genetic results from 3 ancestries (Europeans, Africans, and Admixed Americans) and meta-analyses are populated in GnuMoM2b. In conclusion, GnuMoM2b is a valuable resource for extraction of pregnancy-related genetic results and shows the potential to facilitate meaningful discoveries.

Development and validation of a nomogram to predict spontaneous preterm birth in singleton gestation with short cervix and no history of spontaneous preterm birth

Background

Spontaneous preterm birth (sPTB) stands as a leading cause of neonatal mortality. Consequently, preventing sPTB has emerged as a paramount concern in healthcare. Therefore, our study aimed to develop a nomogram, encompassing patient characteristics and cervical elastography, to predict sPTB in singleton pregnancies. Specifically, we targeted those with a short cervix length (CL), no history of sPTB, and who were receiving vaginal progesterone therapy.

Methods

A total of 568 patients were included in this study. Data from 392 patients, collected between January 2016 and October 2019, constituted the training cohort. Meanwhile, records from 176 patients, spanning November 2019 to January 2022, formed the validation cohort. Following the univariate logistic regression analysis, variables exhibiting a P-value less than 0.05 were integrated into a multivariable logistic regression analysis. The primary objective of this subsequent analysis was to identify the independent predictors linked to sPTB in the training cohort. Next, we formulated a nomogram utilizing the identified independent predictors. This tool was designed to estimate the likelihood of sPTB in singleton pregnancies, particularly those with a short CL, devoid of any sPTB history, and undergoing vaginal progesterone therapy. The C-index, Hosmer-Lemeshow (HL) test, calibration curves, decision curve analysis (DCA), and receiver operating characteristic (ROC) were used to validate the performance of the nomogram.

Results

Upon finalizing the univariate analysis, we progressed to a multivariable analysis, integrating 8 variables with P < 0.05 from the univariate analysis. The multivariable analysis identified 7 independent risk factors: maternal age (OR = 1.072; P < 0.001), cervical length (OR = 0.854; P < 0.001), uterine curettage (OR = 7.208; P < 0.001), GDM (OR = 3.570; P = 0.006), HDP (OR = 4.661; P = 0.003), C-reactive protein (OR = 1.138; P < 0.001), and strain of AI (OR = 7.985; P < 0.001). The nomogram, tailored for sPTB prediction, was grounded on these 7 independent predictors. In predicting sPTB, the C-indices manifested as 0.873 (95% CI, 0.827-0.918) for the training cohort and 0.916 (95%CI, 0.870-0.962) for the validation cohorts, underscoring a good discrimination of the model. Additionally, the ROC curves served to evaluate the discrimination of nomogram model across both cohorts. Calibration curves were delineated, revealing no statistically significant differences in both the training (χ2 = 5.355; P = 0.719) and validation (χ2 = 2.708; P = 0.951) cohorts as evidenced by the HL tests. Furthermore, the DCA underscored the model's excellence as a predictive tool for sPTB.

Conclusions

By amalgamating patient characteristics and cervical elastography data from the second trimester, the nomogram emerged as a visually intuitive and dependable tool for predicting sPTB. Its relevance was particularly pronounced for singleton pregnancies characterized by a short CL, an absence of prior sPTB incidents, and those receiving vaginal progesterone therapy.

Searching and visualizing genetic associations of pregnancy traits by using GnuMoM2b

Adverse pregnancy outcomes (APOs) are major risk factors for women's health during pregnancy and even in the years after pregnancy. Due to the heterogeneity of APOs, only few genetic associations have been identified. In this report, we conducted genome-wide association studies (GWAS) of 479 traits that are possibly related to APOs using a large and racially diverse study, Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b). To display the extensive results, we developed a web-based tool GnuMoM2b ( https://gnumom2b.cumcobgyn.org/ ) for searching, visualizing, and sharing results from GWAS of 479 pregnancy traits as well as phenome-wide association studies (PheWAS) of more than 17 million single nucleotide polymorphisms (SNPs). The genetic results from three ancestries (Europeans, Africans, and Admixed Americans) and meta-analyses are populated in GnuMoM2b. In conclusion, GnuMoM2b is a valuable resource for extraction of pregnancy-related genetic results and shows the potential to facilitate meaningful discoveries.

Change in prevalence of preterm birth in Israel following publication of national guidelines recommending routine sonographic cervical-length measurement at 19-25 weeks' gestation

OBJECTIVE

To compare the prevalence of preterm birth (PTB) (delivery before 37 weeks) in Israel before and after publication of national guidelines recommending second-trimester sonographic cervical-length (CL) measurement.

METHODS

The Israeli Society of Obstetrics and Gynecology (ISOG) guidelines, issued on 1 January 2012, specified that CL should be measured transabdominally or, if this is not possible, transvaginally, at the 19-25-week ultrasound anomaly scan and that CL < 25 mm should indicate further work-up and treatment, although the type of treatment was unspecified. In 2000, the Israel Ministry of Health issued a legal requirement for the submission of delivery records to a national registry. These data were used to compare PTB prevalence in the period before (2000-2011) and that after (2012-2020) publication of the guidelines, as well as trends within each time period. Information was available on singleton and multiple pregnancy and maternal age and parity, as well as low birth weight (< 2500 g).

RESULTS

During the period 2000-2020, there were 3 403 976 infants liveborn in Israel: 1 797 657 before and 1 606 319 after publication of the ISOG guidelines. There were 247 187 PTBs overall, with a prevalence of 7.64% (95% CI, 7.52-7.77%) before publication of the guidelines and 6.84% (95% CI, 6.43-7.24%) afterwards (P < 0.0002, two-tailed). The annual PTB prevalence was static in the first time period but declined by 0.18% per annum during the second period, after publication of the guidelines. The proportionate reduction in PTB prevalence after compared with before publication of the guidelines was 10% overall, 9% for PTB at 33-36 weeks, 18% for PTB at 28-32 weeks and 24% for PTB at < 28 weeks. After publication of the guidelines, reduced prevalence of PTB was observed among singletons (5.49% before vs 4.83% after, P < 0.0001), but not among infants in twin or higher-order multiple pregnancy. There was a statistically significant reduction in the rate of PTB following publication of the guidelines in both nulliparous and parous women and in the 19-39-year-old maternal-age group. Although reductions in PTB prevalence were also noted in high-risk age groups (maternal age < 19 years and ≥ 40 years), these did not reach statistical significance. Following publication of the guidelines, there was a statistically significant reduction in the prevalence of birth weight under 2500 g, of a magnitude similar to that for PTB prevalence.

CONCLUSIONS

The publication of national guidelines recommending routine CL measurement at the time of the second-trimester anomaly scan was associated with a fall in PTB prevalence in singleton pregnancies. Whilst direct evidence linking screening with this fall in prevalence is lacking, it is likely that implementation of routine CL screening played an important role in the reduction of PTB rate. Our experience indicates that screening can be incorporated into the second-trimester anomaly scan. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Study protocol to quantify the genetic architecture of sonographic cervical length and its relationship to spontaneous preterm birth

INTRODUCTION

A short cervix (cervical length <25 mm) in the midtrimester (18-24 weeks) of pregnancy is a powerful predictor of spontaneous preterm delivery. Although the biological mechanisms of cervical change during pregnancy have been the subject of extensive investigation, little is known about whether genes influence the length of the cervix, or the extent to which genetic factors contribute to premature cervical shortening. Defining the genetic architecture of cervical length is foundational to understanding the aetiology of a short cervix and its contribution to an increased risk of spontaneous preterm delivery.

METHODS/ANALYSIS

The proposed study is designed to characterise the genetic architecture of cervical length and its genetic relationship to gestational age at delivery in a large cohort of Black/African American women, who are at an increased risk of developing a short cervix and delivering preterm. Repeated measurements of cervical length will be modelled as a longitudinal growth curve, with parameters estimating the initial length of the cervix at the beginning of pregnancy, and its rate of change over time. Genome-wide complex trait analysis methods will be used to estimate the heritability of cervical length growth parameters and their bivariate genetic correlation with gestational age at delivery. Polygenic risk profiling will assess maternal genetic risk for developing a short cervix and subsequently delivering preterm and evaluate the role of cervical length in mediating the relationship between maternal genetic variation and gestational age at delivery.

ETHICS/DISSEMINATION

The proposed analyses will be conducted using deidentified data from participants in an IRB-approved study of longitudinal cervical length who provided blood samples and written informed consent for their use in future genetic research. These analyses are preregistered with the Center for Open Science using the AsPredicted format and the results and genomic summary statistics will be published in a peer-reviewed journal.

Guidelines on prevention of preterm birth

This guideline has been prepared by the National Maternal Fetal Medicine guidelines committee and approved by the Society of Obstetricians and Gynecologists Pakistan. These recommendations will enable the practicing clinicians to optimally manage pregnancies at risk of preterm birth.

Cervical length distribution and other sonographic ancillary findings of singleton nulliparous patients at midgestation

BACKGROUND

Short cervix at midgestation, the presence of intraamniotic debris, and cervical funneling are risk factors for preterm birth; however, cervical length measurements and cutoffs are not well documented among pregnant patients of different gestational ages and self-reported races and ethnicities.

OBJECTIVE

This study aimed to describe the distribution of cervical length and frequency of funneling and debris at midgestation in nulliparous women by gestational age and race/ethnicity.

STUDY DESIGN

This secondary analysis of screening data from a multicenter treatment trial of singleton nulliparous patients with short cervix was conducted at 14 geographically distributed, university-affiliated medical centers in the United States. Singleton nulliparous patients with no known risk factors for preterm birth were screened for trial participation and asked to undergo a transvaginal ultrasound to measure cervical length by a certified sonographer. The distribution of cervical length and the frequency of funneling and debris were assessed for each gestational age week (16-22 weeks) and stratified by self-reported race and ethnicity, which for this study were categorized as White, Black, Hispanic, and other. Patients enrolled in the randomized trial were excluded from this analysis.

RESULTS

A total of 12,407 nulliparous patients were included in this analysis. The racial or ethnic distribution of the study participants was as follows: White, 41.6%; Black, 29.6%; Hispanic, 24.2%; and others, 4.6%. The 10th percentile cervical length for the entire cohort was 31.1 mm and, when stratified by race and ethnicity, 31.9 mm for White, 30.2 mm for Black, 31.4 mm for Hispanic, and 31.2 mm for patients of other race and ethnicity (P<.001). At each gestational age, the cervical length corresponding to the tenth percentile was shorter in Black patients. The 25 mm value commonly used to define a short cervix and thought to represent the 10th percentile ranged from 1.3% to 5.4% across gestational age weeks and 1.0% to 3.8% across race and ethnicity groups. Black patients had the highest rate of funneling (2.6%), whereas Hispanic and Black patients had higher rates of intraamniotic debris than White and other patients (P<.001).

CONCLUSION

Black patients had shorter cervical length and higher rates of debris and funneling than White patients. The racial and ethnic disparities in sonographic midtrimester cervical findings may provide insight into the racial disparity in preterm birth rates in the United States.

Can sonographic changes in cervical length during pregnancy predict the need for cervical ripening in term pregnancies?

PURPOSE

To evaluate the effect of changes in sonographic cervical length (CL) measured at 14-16 and 21-24 weeks of gestation, on cervical ripening in term pregnancies.

METHODS

This retrospective, cohort study included term pregnancies with CL measured with transvaginal sonography (CL₁ at 14-16 weeks gestation and CL₂ at 21-24 weeks). History of preterm labor, multiple gestations, planned caesarean section, fetal anomalies and stillbirths were excluded. Participants were grouped based on ≥ 10% vs. < 10% CL shortening between measurements. The primary outcome was whether cervical shortening < 10% between CL₁ and CL₂ was associated with increased use of cervical ripening. Secondary outcomes were gestational age at delivery, delivery mode and birthweight.

RESULTS

Among 267 women who met the inclusion criteria, CL decreased ≥ 10% between scans in 70 (26.3%) and < 10% in 197 (73.7%). Baseline characteristics were similar between groups. Fewer women with ≥ 10% shortening between scans, underwent cervical ripening (7.1% vs. 16.8%, p < 0.05). In addition, in the ≥ 10% group, although CL₂ was in the normal range, it was shorter than in the < 10% group (34.3 ± 6.7 mm vs. 40.1 ± 6.4 mm, p < 0.01).

CONCLUSION

Decrease in cervical length > 10% between 14-16 and 21-24-weeks' gestation is associated with lower use of cervical ripening at term.

Cervical Assessment for Predicting Preterm Birth-Cervical Length and Beyond

Preterm birth is considered one of the main etiologies of neonatal death, as well as short- and long-term disability worldwide. A number of pathophysiological processes take place in the final unifying factor of cervical modifications that leads to preterm birth. In women at high risk for preterm birth, cervical assessment is commonly used for prediction and further risk stratification. This review outlines the rationale for cervical length screening for preterm birth prediction in different clinical settings within existing and evolving new technologies to assess cervical remodeling.

Serial cervical-length measurements after first episode of threatened preterm labor improve prediction of spontaneous delivery prior to 37 weeks' gestation

OBJECTIVE

To assess whether repeat cervical-length (CL) measurement in women discharged from hospital after their first episode of threatened preterm labor can predict their risk of spontaneous preterm birth.

METHODS

This was a secondary analysis of a randomized controlled trial of maintenance tocolysis, in which CL was measured on transvaginal ultrasound at the time of hospital discharge and after 2, 4, 8 and 12 weeks, in women who remained undelivered after their first episode of threatened preterm labor. After univariate analysis, multivariate logistic regression analysis was used to assess whether CL < 10 mm at the time of hospital discharge or at any follow-up evaluation could predict spontaneous delivery prior to 37 weeks of gestation.

RESULTS

Of 226 women discharged after a diagnosis of threatened preterm labor, 57 (25.2%) delivered spontaneously prior to 37 weeks' gestation. The risk of spontaneous preterm birth was higher among women with CL < 10 mm at hospital discharge compared to those with CL ≥ 10 mm (adjusted odds ratio (aOR), 3.3; 95% CI, 1.2-9.2). Moreover, spontaneous preterm delivery was more common when CL < 10 mm was detected up to 2 weeks (aOR, 2.9; 95% CI, 1.1-7.3) or up to 4 weeks (aOR, 7.3; 95% CI, 2.3-22.8) post discharge, as compared with when CL was persistently ≥ 10 mm. The association was not significant when considering CL measurements at 8 weeks, and there was insufficient information to assess the effect of measurements obtained at 12 weeks.

CONCLUSIONS

Women who remain undelivered after their first episode of threatened preterm labor continue to be at high risk of spontaneous preterm birth if their CL is below 10 mm at the time of hospital discharge or at any follow-up visit up to 4 weeks later. CL measurement could be included in the antenatal care of these women in order to stratify their risk of preterm birth, rationalize resource utilization and help clinicians improve pregnancy outcome. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Current Preterm Birth Prevention Strategies

Preterm birth remains a major issue in obstetrics. Despite efforts to reduce the incidence of preterm delivery, rates in the United States remain high at 10.2% of all live births with an incidence of 10.8% globally. Preterm birth is the leading cause of neonatal morbidity and mortality worldwide. It is also the leading cause of death in children younger than 5 years. Research into this important health topic has allowed for the identification of risk factors for preterm birth, the most important of which is a history of prior preterm birth. Cervical length screening may allow us to identify those at greatest risk of recurrent preterm birth as well as a de novo risk in women with no prior preterm birth history.

Predicting labor induction success by cervical funneling in uncomplicated pregnancies

Aim

Predictive accuracy of cervical funneling for successful vaginal delivery prior to labor induction was compared to that of conventional methods such as Bishop score and cervical length.

Methods

Prospective observational study was conducted on nulliparous women at 38 gestational weeks or more with intact membranes who delivered vaginally following labor induction. Transvaginal ultrasound was performed prior to labor induction to evaluate the cervix, to determine the cervical length and to check for the presence of funneling. Following pelvic examinations, the Bishop score was calculated. Predictive accuracy of the three different methods, namely cervical funneling, cervical length and Bishop, were compared.

Results

A total of 235 nulliparous women with intact membranes were recruited. Of these, 194 women (82.6%) had successful vaginal deliveries following induction. Cervical funneling was observed in 105 women (44.7%). The rate of successful vaginal delivery was significantly higher in women with cervical funneling than in those without funneling (90.5% vs 76.2%, P < 0.004). Multivariable analysis showed that cervical funneling, similar to traditional measures such as the Bishop score and cervical length, was an independent predictor of successful vaginal delivery following labor induction (odds ratio = 2.95; 95% confidence interval: 1.38–6.47; P = 0.007).

Conclusions

Similar to the conventional methods of cervical evaluation, such as the Bishop score and cervical length, cervical funneling may serve as a useful and valid predictor of successful vaginal deliveries prior to labor induction.

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.

Cervical assessment by ultrasound for preventing preterm delivery

BACKGROUND

Measurement of cervical length by ultrasound is predictive of preterm birth (PTB). There are three methods of ultrasound cervical assessment: transvaginal (TVU), transabdominal (TAU), and transperineal (TPU, also called translabial). Cervical length measured by TVU is a relatively new screening test, and has been associated with better prediction of PTB than previously available tests. It is unclear if cervical length measured by ultrasound is effective for preventing PTB. This is an update of a review last published in 2013.

OBJECTIVES

To assess the effectiveness of antenatal management based on transvaginal, transabdominal, and transperineal (also called translabial) ultrasound screening of cervical length for preventing preterm birth.

SEARCH METHODS

For this update, we searched the Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform (ICTRP) to 30 August 2018; reviewed the reference lists of all articles, and contacted experts in the field for additional and ongoing trials.

SELECTION CRITERIA

We included published and unpublished randomised controlled trials (RCT) including pregnant women between the gestational ages of 14 to 32 weeks, for whom the cervical length was screened for risk of PTB with TVU, TAU, or TPU. This review focused on studies based on knowledge versus no knowledge of cervical length results, or ultrasound versus no ultrasound for cervical length. We excluded studies based on interventions (e.g. progesterone, cerclage) for short cervical length.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods.

MAIN RESULTS

We included seven RCTs (N = 923): one examined asymptomatic women with twin pregnancies; four included women with singleton pregnancies and symptoms of preterm labour (PTL); one included women with singleton pregnancies and symptoms of preterm premature rupture of membranes (PPROM); and one included asymptomatic singletons. All trials used TVU for screening.We assessed the risk of bias of the included studies as mixed, and the quality of the evidence for primary outcomes as very low for all populations.For asymptomatic women with twin pregnancies, it is uncertain whether knowledge of TVU-measured cervical length compared to no knowledge reduces PTB at less than 34 weeks (risk ratio (RR) 0.62, 95% confidence intervals (CI) 0.30 to 1.25; 1 study, 125 participants) because the quality of the evidence is very low. The results were also inconclusive for preterm birth at 36, 32, or 30 weeks; gestational age at birth, and other maternal and perinatal outcomes.Four trials examined knowledge of TVU-measured cervical length of singletons with symptoms of PTL versus no knowledge. We are uncertain of the effects because of inconclusive results and very low-quality evidence for: preterm births at less than 37 weeks (average RR 0.59, 95% CI 0.26 to 1.32; 2 studies, 242 participants; I² = 66%; Tau² = 0.23). Birth occurred about four days later in the knowledge groups (mean difference (MD) 0.64 weeks, 95% CI 0.03 to 1.25; 3 trials, 290 women). The results were inconclusive for the other outcomes for which there were available data: PTB at less than 34 or 28 weeks; birthweight less than 2500 g; perinatal death; maternal hospitalisation; tocolysis; and steroids for fetal lung maturity.The trial of singletons with PPROM (N = 92) evaluated safety of using TVU to measure cervical length in this population as its primary outcome, not its effect on management. The results were inconclusive for incidence of maternal and neonatal infections between the TVU and no ultrasound groups.In the trial of asymptomatic singletons (N = 296), in which women either received TVU or not, the results were inconclusive for preterm birth at less than 37 weeks (RR 1.27, 95% CI 0.61 to 2.61; I² = 0%), gestational age at birth, and other perinatal and maternal outcomes.We downgraded evidence for limitations in study design, inconsistency between the trials, and imprecision, due to small sample size and wide confidence intervals crossing the line of no effect.No trial compared the effect of knowledge of the CL with no knowledge of CL in other populations, such as asymptomatic women with singleton pregnancies, or symptomatic women with twin pregnancies.

AUTHORS' CONCLUSIONS

There are limited data on the effects of knowing the cervical length, measured by ultrasound, for preventing preterm births, which preclude us from drawing any conclusions for women with asymptomatic twin or singleton pregnancies, singleton pregnancies with PPROM, or other populations and clinical scenarios.Limited evidence suggests that knowledge of transvaginal ultrasound-measured cervical length, used to inform the management of women with singleton pregnancies and symptoms of preterm labour, appears to prolong pregnancy by about four days over women in the no knowledge groups.Future studies could look at specific populations separately (e.g. singleton versus twins; symptoms versus no symptoms of PTL), report on all pertinent maternal and perinatal outcomes, and include cost-effectiveness analyses. Most importantly, future studies should include a clear protocol for management of women based on TVU-measured cervical length.

Evaluation of the effectiveness of foetal fibronectin as a predictor of preterm birth in symptomatic preterm labour women

BACKGROUND

The prediction of preterm birth (PTB) is important in the management of symptomatic preterm labour women. We evaluated the effectiveness of the foetal fibronectin (fFN) test for predicting PTB in symptomatic preterm labour women with consideration of physiologic changes in cervical length (CL) during pregnancy.

METHODS

This prospective study included 85 women with symptomatic preterm labour of a singleton pregnancy. Positive fFN was defined as a fFN level of > 50 ng/mL in cervicovaginal secretion, while a short CL was defined as that below 25th percentile at the corresponding gestational age. We evaluated effectiveness of the fFN test, CL, and the combination of these two tests, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), positive likelihood ratio (LR⁺), negative likelihood ratio (LR^-) to predict the PTB within 7 and 14 days of testing and PTB at < 34 and 37 weeks of gestation. We also present the odds ratios (ORs) of the test results, defining the women with both negative results as the reference group.

RESULTS

Of the 85 women, 31 (36.5%) showed a positive fFN and 44 (51.8%) had a short CL. PTB occurred within 7 and 14 days of testing and before 34 and 37 weeks of gestation in 17.6, 20.0, 23.5 and 49.4% of the women, respectively. The fFN and CL results showed low predictive effectiveness for the studied outcomes with LR⁺ (fFN, 1.5-1.9; CL, 1.0-1.5) and LR^- (fFN, 0.7; CL, 0.7-0.9). The combined use of fFN and CL could not improve these results (LR⁺, 1.4-2.3; LR^-, 0.7-0.9). However, the risk of PTB before 37 weeks was increased in women with positive fFN but not CL shortening compared to the reference group (odds ratio [OR], 3.8; 95% confidence interval [CI], 1.1-1.3). The risk of PTB before 34 weeks was increased in both positive fFN and CL compared to the reference group (OR, 8.1; 95% CI, 1.9-34.5).

CONCLUSION

Although, our approach could not improve the ability to predict PTB, it could identify women at risk for delivery before 34 or 37 weeks of gestation. Therefore, it could be used to manage women with symptomatic preterm labour.

Fetal fibronectin test for threatened preterm delivery 48h after admission: Cost-effectiveness study

OBJECTIVE

The aim of this work was to assess the cost-effectiveness of the fetal fibronectin (fFN) test at 48 h after admission for threatened preterm delivery to promote early discharge.

STUDY DESIGN

Before-and-after study to calculate the incremental cost-effectiveness ratio (ICER). Patients were enrolled 48 h after admission in a tertiary care centre for threatened preterm delivery between 24⁺⁰ and 34⁺⁶ weeks. fFN testing was performed. During the first period, physician was blinded to fFN test and discharge occurred after apparent reduced symptomatology at physician's discretion. During the second period, fFN test was revealed to physician and discharge was immediately proposed to negative test patients. The costs considered in this analysis were the direct medical costs from the hospital perspective: costs of hospitalisation, treatment, and imaging procedures. The efficacy criterion selected was the number of deliveries at 7 and at 14 days after admission for threatened preterm delivery.

RESULTS

The study included 178 pregnant patient, 99 during the first period (July 2008-October 2009) and 79 during the second (March 2010-February 2012). The lengths of hospital stays were shorter during the second period, with more than 50% of women discharged home between 48 and 72 h (p < 0.0001) resulting in a cost-saving of 76 051 euros. The number of deliveries at 7 and at 14 days was similar between the two periods.

CONCLUSION

The fFN test at 48 h after admission supported early discharge and was safe and cost-effective.

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.

Safety and efficacy of the cervical pessary combined with vaginal progesterone for the prevention of spontaneous preterm birth

INTRODUCTION

The aim of this study was to evaluate the safety and efficacy of the combined treatment of cervical pessary and endovaginal progesterone for the prevention of spontaneous preterm birth (SPB) in women with a short cervical length (CL) between 20 and 24 weeks of gestation.

MATERIALS AND METHODS

This is a prospective study of women with a singleton pregnancy and a sonographically detected mid-trimester CL ≤25 mm. The primary outcome measure was spontaneous delivery before 34 weeks (238 days) of gestation.

RESULTS

The study sample consisted of 90 women with a mean CL of 14.2 mm (SD=6.5 mm). Of the women, 34.4% had at least one risk factor for SPB; 7.8% delivered preterm before 34 weeks of gestation, and 25.6%, before 37 weeks. Neonatal death occurred in two (2.2%) cases due to respiratory distress syndrome. Lower body mass index values, history of preterm delivery and number of second trimester miscarriages were independently associated with delivery before 34 weeks.

CONCLUSION

The combination of vaginal progesterone and cervical pessary for the prevention of SPB in women with a short cervix is safe and well tolerated. This therapy was associated with pregnancy prolongation, reduced prematurity rate and a low rate of perinatal complications.

Accuracy of fetal fibronectin for the prediction of preterm birth in symptomatic twin pregnancies: a pilot study

Our goal was to evaluate the performance of fetal fibronectin (fFN) test alone or combined with cervical length (CL), to predict spontaneous preterm birth (PTB) in symptomatic twin pregnancies. We carry out a short pilot study including all uncomplicated diamniotic twin pregnancies with symptoms of preterm labor (PTL) and intact membranes at 24-33 weeks + 6 days of gestation. Studied outcome were spontaneous delivery within 7 and 14 days of testing and spontaneous PTB at <34 and <37 weeks of gestation. Among 40 women, fFN test was positive in 3 of them (7.5%). Regardless of the outcome studied CL did not significantly predict PTB. Performance of fFN was sensitivity (66.7%), specificity (97.2%), positive predictive value (66.7%), negative predictive value (97.2%), positive likelihood ratio (LR) (24.0), and negative LR (0.3) to predict spontaneous PTB within 7 days (p = 0.01). Thus, 66.1% of patients with a positive fFN test would deliver within 7 days versus 2.4% if negative testing; starting with a pre-test probability of 7.5%. Combining CL and fFN did not enable to increase enough positive LR or decrease significantly negative LR. In conclusion, fFN test alone might have a better ability to detect spontaneous delivery within 7 days among symptomatic twin pregnancies.

Current options for mechanical prevention of preterm birth

Cervical insufficiency can be defined by a combination of obstetric history, cervical dilation on exam, and/or short cervical length in women with prior preterm birth. Options for mechanical intervention include cerclage and pessary. There is evidence to support the benefit of a cervical cerclage in women with singleton gestations who have a diagnosis of cervical insufficiency either based on second trimester painless cervical dilatation leading to recurrent early preterm births, or a history of early spontaneous preterm birth and a second trimester transvaginal ultrasound short cervical length or cervical dilation on exam. For women with multiple gestations, the benefit of a cerclage is uncertain, and further study is warranted. The pessary has also been studied for mechanical prevention of preterm birth in various populations, however the results so far have been mixed and warrants further study prior to routine use.

Prevention of preterm birth: Novel interventions for the cervix

Preterm birth is the leading cause of neonatal mortality and morbidity worldwide. Spontaneous preterm birth is a complex, multifactorial condition in which cervical dysfunction plays an important role in some women. Current treatment options for cervical dysfunction include cerclage and supplemental progesterone. In addition, cervical pessary is being studied in research protocols. However, cerclage, supplemental progesterone and cervical pessary have well known limitations and there is a strong need for alternate treatment options. In this review, we discuss two novel interventions to treat cervical dysfunction: (1) injectable, silk protein-based biomaterials for cervical tissue augmentation (injectable cerclage) and (2) a patient-specific pessary. Three-dimensional computer simulation of the cervix is performed to provide a biomechanical rationale for the interventions. Further development of these novel interventions could lead to new treatment options for women with cervical dysfunction.

Sonographic Measurement of Cervical Volume in Pregnant Women at High Risk of Preterm Birth Using a Geometric Formula for a Frustum Versus 3-Dimensional Automated Virtual Organ Computer-Aided Analysis

OBJECTIVES

To compare cervical volume measurements by 3-dimensional (3D) sonography using Virtual Organ computer-aided analysis (VOCAL; GE Healthcare, Milwaukee, WI) versus a manual method using a geometric formula for a frustum.

METHODS

We included 142 asymptomatic pregnant women at 16 to 24 weeks gestation at high risk for preterm birth. With a Voluson 730 Expert system (GE Healthcare), they underwent 2-dimensional (2D) transvaginal sonographic cervical length measurements and 3D cervical volume acquisition. The stored volumes were processed by VOCAL on a surface tablet. Cervical volume was manually calculated from the 2D images by using the formula V = 1/3 × π × h × (r1²  + r2²  + r1 × r2), where V represents cervical volume; π was approximated as 3.14159; h, cervical length; r1, radius at the internal os; and r2, radius at the external os.

RESULTS

Cervical volume was lower when obtained manually than by VOCAL, with a coefficient of variation of 30%, a mean difference of 10.1 ± 14.9 cm³ (P < .0001), and a poor interclass correlation coefficient of 0.62 (95% confidence interval [CI], 0.31 to 0.78). Both methods had good reproducibility; however, VOCAL had wider limits of agreement. A positive correlation was found between both methods (r = 0.63; P < .0001). No correlation was found between cervical length by 2D transvaginal ultrasound and cervical volume by the VOCAL technique (r = 0.06; 95% CI, -0.10 to 0.22) or cervical volume by the manual method (r = 0.2; 95% CI, 0.08 to 0.39).

CONCLUSIONS

The cervix represents a frustum (truncated cone, r1 is not equal to r2) in shape rather than a cylinder. Both methods are reproducible; VOCAL is less reliable but provides higher values of cervical volume.

Performance of cervical phIGFBP-1 test alone or combined with short cervical length to predict spontaneous preterm birth in symptomatic women

We aimed to assess the accuracy of cervical phosphorylated insulin-like growth factor binding protein-1 (phIGFBP-1) test alone or in combination with cervical length (CL), to predict preterm birth (PTB) in symptomatic women. We performed a prospective cohort study from 2012 to 2015 including singleton pregnancies with symptoms of preterm labor, intact membranes and CL < 25 mm at 24-34 weeks of gestation. Studied outcome were spontaneous delivery within 7 and 14 days of testing and spontaneous PTB at <34 and <37 weeks of gestation. Among 180 women, 21 (11.7%) had a positive phIGFBP-1 test. Spontaneous PTB occurred within 7 days, 14 days of testing and before 34 weeks and 37 weeks in 7.8%, 10.6%, 12.9% and 28.8%, respectively. The phIGFBP-1 test had a low predictive performance for all studied outcomes varying for positive likelihood ratios (2.8 to 3.4) and negative likelihood ratios (0.8). Combining phIGFBP-1 and CL did not increase its predictive ability. After adjustment, positive phIGFBP-1 test was no more independently associated with a delivery within 7 days (p = 0.55), unlike CL < 15 mm (p = 0.04). In conclusion, phIGFBP-1 test alone or in combination with CL has a low predictive accuracy to predict PTB in symptomatic women.

Progestogens for Maintenance Tocolysis in Women With a Short Cervix: A Randomized Controlled Trial

OBJECTIVE

To assess the efficacy of progestogens for maintenance tocolysis in women undelivered after their first preterm labor episode.

METHODS

Women with singleton pregnancies between 22 0/7 and 31 6/7 weeks of gestation with arrested preterm labor and a cervical length 25 mm or less at hospital discharge were eligible. Patients with a previous preterm birth were excluded. In a randomized controlled trial conducted in five university hospitals, women were randomized to receive vaginal progesterone (200 mg per day) or intramuscular 17α-hydroxyprogesterone caproate (341 mg per week) or to an observation groups (control group). The primary outcome was the proportion of women with preterm birth at less than 37 weeks of gestation. A sample size of 160 per group (n=480) was planned to compare vaginal progesterone and 17α-hydroxyprogesterone caproate groups with those in the control group. The sample size estimation was based on the hypothesis that the risk of experiencing preterm birth in the control group would be 30% and that 17α-hydroxyprogesterone caproate or progesterone would decrease this risk to 15%. A P value of <.025 was defined as statistically significant. At planned interim analysis (n=254), the trial was stopped for futility.

RESULTS

Between July 2010 and June 2015, 257 women were eligible and 254 were subsequently randomly assigned to vaginal progesterone (n=86), 17α-hydroxyprogesterone caproate (n=87), or observation (n=81). Nineteen (8%) were excluded from the analysis because they either dropped out or information was missing, leaving 235 women available for analysis. Demographic characteristics were similar across groups. The preterm birth rate did not differ significantly between groups: 23% in the 17α-hydroxyprogesterone caproate group, 39% in the vaginal progesterone group, and 22% in the women in the control group (P=.949 for 17α-hydroxyprogesterone caproate compared with the women in the control group and P=.027 for vaginal progesterone compared with women in the control group).

CONCLUSION

The use of progestogens for maintenance tocolysis in women with a short cervix did not reduce the rate of preterm birth.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT01178788.

Frequency and clinical significance of short cervix in patients with preterm premature rupture of membranes

Objective

Cervical length measurement has been uggested as a useful tool for predicting intra-amniotic infection/inflammation in preterm labor, but little information is available in the setting of preterm premature rupture of membranes (pPROM). We aimed to determine whether a short cervical length is independently associated with an increased risk of intra-amniotic infection or inflammation and impending preterm delivery in women with pPROM.

Methods

This was a retrospective cohort study involving 171 consecutive singleton pregnant women with pPROM (21+0–33+6 weeks’ gestation), who underwent amniocentesis. Amniotic fluid (AF) was cultured, and assayed for interleukin (IL)-6 and IL-8. Cervical length was measured at the time of amniocentesis by transvaginal ultrasonography with an aseptic technique. Short cervical length was defined as a cervical length of ≤15 mm. Intra-amniotic infection was defined as a positive AF culture for microorganisms and intra-amniotic inflammation was defined as elevated AF concentrations of IL-6 or IL-8 (IL-6 ≥1.5 ng/mL and/or IL-8 ≥1.3 ng/mL).

Results

Fifty (29.2%) women had a sonographic cervical length of ≤15mm. On univariate analysis, short cervical length was associated with an increased risk for intra-amniotic infection and/or inflammation; no other parameters studied showed a significant association. Multivariable analyses indicated that short cervical length was significantly associated with a higher risk of impending preterm delivery (within 2 days of measurement, within 7 days of measurement, and before 34 weeks), and remained significant after adjustment for potential confounders.

Conclusion

In women with pPROM, short cervical length is associated with an increased risk for intra-amniotic infection/inflammation and associated with impending preterm delivery, independent of the presence of intra-amniotic infection/inflammation.

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.

The interaction between vaginal microbiota, cervical length, and vaginal progesterone treatment for preterm birth risk

BACKGROUND

Preterm birth is the primary cause of infant death worldwide. A short cervix in the second trimester of pregnancy is a risk factor for preterm birth. In specific patient cohorts, vaginal progesterone reduces this risk. Using 16S rRNA gene sequencing, we undertook a prospective study in women at risk of preterm birth (n = 161) to assess (1) the relationship between vaginal microbiota and cervical length in the second trimester and preterm birth risk and (2) the impact of vaginal progesterone on vaginal bacterial communities in women with a short cervix.

RESULTS

Lactobacillus iners dominance at 16 weeks of gestation was significantly associated with both a short cervix <25 mm (n = 15, P < 0.05) and preterm birth <34⁺⁰ weeks (n = 18; P < 0.01; 69% PPV). In contrast, Lactobacillus crispatus dominance was highly predictive of term birth (n = 127, 98% PPV). Cervical shortening and preterm birth were not associated with vaginal dysbiosis. A longitudinal characterization of vaginal microbiota (<18, 22, 28, and 34 weeks) was then undertaken in women receiving vaginal progesterone (400 mg/OD, n = 25) versus controls (n = 42). Progesterone did not alter vaginal bacterial community structure nor reduce L. iners-associated preterm birth (<34 weeks).

CONCLUSIONS

L. iners dominance of the vaginal microbiota at 16 weeks of gestation is a risk factor for preterm birth, whereas L. crispatus dominance is protective against preterm birth. Vaginal progesterone does not appear to impact the pregnancy vaginal microbiota. Patients and clinicians who may be concerned about "infection risk" associated with the use of a vaginal pessary during high-risk pregnancy can be reassured.

Review: Eicosanoids in preterm labor and delivery: Potential roles of exosomes in eicosanoid functions

Preterm delivery is a major obstetric health problem contributing to poor neonatal outcome including low birth weight, respiratory distress syndrome, gastrointestinal, immunologic, central nervous system, hearing, and vision problems. Worldwide, approximately 15 million babies are born prematurely each year. The critical question which remains is how to identify women destined to deliver preterm from those who will achieve a term delivery. Prostaglandins, in all mammals, are important in the parturient process. Increased intrauterine prostaglandin production is associated with labor and in fact prostaglandin E₂ (PGE₂) or analogs are widely used clinically for cervical ripening and labor induction. Measurements of circulating eicosanoids have been problematic because of the rapid and major clearance by the lungs and then kidneys resulting in very low concentrations in plasma. Moreover, since eicosanoids are produced by all mammalian tissues, the sources of the measured eicosanoids are unknown. Our understanding of how cells communicate has undergone a paradigm shift with the recognition of the role of exosomes in intercellular signaling. Recent publications have identified enzymes and products of arachidonic acid metabolism (eicosanoids) within exosomes. This review will explore the potential roles of exosomes in eicosanoid functions that are critical in preterm labor and delivery.

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.

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).

Changes in Cervical Nitric Oxide Concentration Correlate With Bishop Score and Cervical Length Modifications in Prostaglandin E2-Mediated Induction of Labor

OBJECTIVE

Nitric oxide (NO) plays a fundamental role in cervical ripening and it is synthesized in the human cervix. We studied the effect of the dinoprostone on cervical NO release in pregnant women, and we investigated the relationship between cervical NO metabolites, cervical length, and Bishop score.

METHODS

Seventy-seven women underwent induction of labor at > or = 37 weeks of gestation, due to post-term pregnancy (23.8%), oligohydramnios (36.3) or preeclampsia (29.9%). Cervical fluid samples for NO metabolites (NOx), Bishop score, and cervical length were assessed immediately before (time 0 [T0]) and 6 hours after (T6) the local application of dinoprostone, a commercially available prostaglandin E2 (PGE2) analog.

RESULTS

The mean patients' age was 34 +/- 3.2 years, mean gestational age at enrollment was 284 +/- 9.2 days, and nulliparous represented 31.2% of the study population. At time 0, Bishop score was less than 4 in 74% (57/77) of the subjects, mean cervical length was 28.6 +/- 5.8 mm, mean NOx concentration was 208.6 +/- 103.8 microM/mL; 6 hours later, at T6, the mean cervical length decreased to 19.5 +/- 8.8 mm, and the mean NOx concentration increased up to 316.7 +/- 240.9 microM/mL. Data were unaffected by parity or by regular uterine contraction patterns. A statistically significant positive correlation was found between changes in cervical NOx levels and Bishop score modification (P < .01; r = .494), as well as between the modification of NO metabolites concentration and cervical shortening (P < .01; r = .307).

CONCLUSIONS

Prostaglandin (PG)-induced cervical ripening is associated with local NO release. NO plays an active role in cervical remodeling since it positively correlates with both cervical shortening and Bishop score increase. NO oxide and PG are the two pathways that, cross activating each other, trigger the cascade of events responsible of cervical ripening.

[Are ultrasound measurements of the cervical length and fetal head-perineum distance predictive of delivery outcome in post-term pregnancies?]

OBJECTIVE

Post-term pregnancy is frequently associated with higher fetal and maternal morbidity and mortality. Its management essentially depends on clinical cervical characteristics as evaluated by the Bishop score (BS). However, BS is poorly predictive of the delivery outcome. We sought to demonstrate that ultrasound measurement of cervical length and evaluation of fetal height could predict the outcome in post-term pregnancies.

METHODS

A prospective single center study was undertaken between the 21st of January and the 1st of June 2013. Fetal height was measured using a transperineal technique and cervical length was evaluated by a vaginal ultrasound on patients consulting and their term date. C-section rates were considered to be the primary judgment criteria.

RESULTS

A total of 136 patients were included. C-section rates in this population was 19%. Fetal height and cervical length were not different between the C-section group and the vaginal delivery group.

CONCLUSION

Our study demonstrates that ultrasound measurement of cervical length and fetal height do not show better results than BS in predicting the outcome of post-term pregnancy. Combining these ultrasound measurements has already been suggested in other studies and promising results have been shown. More studies are necessary to further these results.

Risk assessment and management to prevent preterm birth

Preterm birth is the most important cause of neonatal mortality and morbidity worldwide. In this review, we review potential risk factors associated with preterm birth and the subsequent management to prevent preterm birth in low and high risk women with a singleton or multiple pregnancy. A history of preterm birth is considered the most important risk factor for preterm birth in subsequent pregnancy. General risk factors with a much lower impact include ethnicity, low socio-economic status, maternal weight, smoking, and periodontal status. Pregnancy-related characteristics, including bacterial vaginosis and asymptomatic bacteriuria, appear to be of limited value in the prediction of preterm birth. By contrast, a mid-pregnancy cervical length measurement is independently associated with preterm birth and could be used to identify women at risk of a premature delivery. A fetal fibronectin test may be of additional value in the prediction of preterm birth. The most effective methods to prevent preterm birth depend on the obstetric history, which makes the identification of women at risk of preterm birth an important task for clinical care providers.

Factors associated with spontaneous preterm birth risk assessed by transvaginal ultrasound following cervical cerclage

OBJECTIVE

To determine the predictive value of various cervical length measurements postcerclage for the outcome of preterm birth following both elective and rescue cerclage.

MATERIALS AND METHODS

Over a five-year period, we identified 59 women who had a transvaginal cerclage inserted followed by serial cervical length measurement. Of these, 18 were elective cerclages placed at 14 weeks of gestation on the basis of a history of cervical insufficiency and 41 were rescue cerclages performed at gestations ranging from 17 to 23 weeks following a diagnosis of shortened cervix on ultrasound. The women were asymptomatic throughout.

RESULTS

There was a strong correlation between cervical length postcerclage and gestation at delivery. For both groups, preterm birth could be predicted by the total cervical length. In the rescue cerclage group, the change in cervical length was predictive, with positive changes associated with later gestation at delivery. The presence of funnelling was predictive of preterm birth in the elective cerclage group only.

CONCLUSION

Transvaginal cervical length measurement is useful in the prediction of preterm birth postcerclage placement. Serial cervical length measurement postcerclage may assist with timely addition of interventions such, progesterone and antenatal cortico steroids for fetal lung maturation.

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.

Sonographically accessed funneling of the uterine cervix as a predictor of successful labor induction

OBJECTIVE

The Bishop score and length of the uterine cervix are good predictors of successful labor induction. However, little is known about the association between the funneling of the uterine cervix and successful labor induction. The study aimed to evaluate cervical funneling as a predictor of successful labor induction.

METHODS

This study was designed as a prospective observational study. Subjects who delivered a baby by labor induction were enrolled in the study from July 2011 to August 2013. Cervical funneling and length were examined with transvaginal ultrasonography. The Bishop score was rated by digital pelvic examination.

RESULTS

A total of 163 primigravida women were recruited for the study. Of these, 137 participants (84.0%) delivered vaginally by labor induction. Cervical funneling was observed in 93 women (57.1%). Successful labor induction was significantly higher in patients with cervical funneling than those without it (91.4% vs. 74.3%, P<0.01), and was significantly associated with cervical funneling, as well as the Bishop score and cervical length. In a multivariate analysis, cervical funneling was an independent predictor for successful vaginal delivery by labor induction ( odd ratio, 2.70; 95% confidence interval, 1.02 to 7.10; P=0.04). However, the Bishop score and cervical length had no association with successful vaginal delivery.

CONCLUSION

This study showed that cervical funneling could be a predictive marker for vaginal delivery during labor induction.

The role of sonographic cervical length in labor induction at term

The purpose of this study is to review the literature examining the role of ultrasound in the induction of labor. Databases including Ovid, PubMed, Web of Science, Google Scholar, and UpToDate were searched and current guidelines from the SOGC, the ACOG, the RCOG, and the RANZCOG were reviewed. Although studies have not demonstrated the superiority of cervical sonography to the Bishop score, the evidence indicates that sonography could be useful in planning induction of labor, significantly reducing the need for cervical ripening agents. A more comprehensive method integrating both sonography and digital exam may be more appropriate.

The role of cervical length in women with threatened preterm labor: is it a valid predictor at any gestational age?

OBJECTIVE

To determine whether the predictive accuracy of sonographic cervical length (CL) for preterm delivery (PTD) in women with threatened preterm labor (PTL) is related to gestational age (GA) at presentation.

STUDY DESIGN

A retrospective cohort study of all women with singleton pregnancies who presented with PTL at less than 34 + 0 weeks and underwent sonographic measurement of CL in a tertiary medical center between 2007 and 2012. The predictive accuracy of CL for PTD was stratified by GA at presentation.

RESULTS

Overall, 1077 women who presented with PTL have had sonographic measurement of CL and met the study inclusion criteria. Of those, 223 (20.7%) presented at 24 + 0-26 + 6 weeks (group 1), 274 (25.4%) at 27 + 0-29 + 6 weeks (group 2), 283 (26.3%) at 30 + 0-31 + 6 weeks (group 3), and 297 (27.6%) at 32 + 0-33 + 6 weeks (group 4). The overall performance CL as a predictive test for PTD was similar in the 4 GA groups, as reflected by the similar degree of correlation between CL with the examination to delivery interval (r = 0.27, r = 0.26, r = 0.28, and r = 0.29, respectively, P = .8), the similar area under the receiver-operator characteristic curve (0.641-0.690, 0.631-0.698, 0.643-0.654, and 0.678-0.698, respectively, P = .7), and a similar decrease in the risk of PTD of 5-10% for each additional millimeter of CL. The optimal cutoff of CL, however, was affected by GA at presentation, so that a higher cutoff of CL was needed to achieve a target negative predictive value for delivery within 14 days from presentation for women who presented later in pregnancy. The optimal thresholds to maximize the negative predictive value for delivery within 14 days were 36 mm, 32.5 mm, 24 mm and 20.5 mm for women who presented at 32 + 0 to 33 + 6 weeks, 30 + 0 to 31 + 6 weeks, 27 + 0 to 29 + 6 weeks and 24 + 0 to 26 + 6, respectively.

CONCLUSION

CL has modest predictive accuracy in women with threatened PTL, regardless of GA at presentation. However, the optimal cutoff of CL for the purpose of clinical decision making in women with PTL needs to be adjusted based on GA at presentation.

Role of 3-dimensional power Doppler sonography in differentiating pregnant women with threatened preterm labor from those with an asymptomatic short cervix

OBJECTIVES

To compare cervical volumes and vascularization indices using 3-dimensional power Doppler sonography among singleton pregnancies with threatened preterm labor and an asymptomatic short cervix.

METHODS

Three hundred asymptomatic healthy pregnant women between 24 and 34.6 gestational weeks were prospectively scanned for cervical length. If cervical length was short, defined as below the 10th percentile for gestational age, the cervical volume and vascularization indices (vascularization index [VI], vascularization-flow index [VFI], and flow index [FI]) were measured. Women receiving any treatment for preterm delivery prevention were excluded. During this period, the same sonographic parameters were measured among patients with threatened preterm labor admitted to our institution during the first 24 hours after admission. Multiple pregnancies and fetal or maternal pathologic conditions, were exclusion criteria. Data on body mass index, maternal age, smoking, parity, family history of preterm birth, mother who was born preterm, and previous preterm birth among the pregnant women were recorded. Sonographic and medical history parameters were compared between the two groups.

RESULTS

Twenty-nine asymptomatic healthy women (9.6%) had a short cervix. Additionally, 71 pregnancies with threatened preterm labor were scanned. There were no statistically significant differences between the groups in medical history parameters or cervical length. The cervical volume was smaller in threatened preterm cases (12.90 versus 17.168 cm(3); P = .005). The VI and VFI were lower in women with an asymptomatic short cervix (VI, 4.369% versus 15.939%; P < .001; VFI, 1.514 versus 4.878; P < .001). The FI was higher in the short cervix group (33.581 versus 30.311; P = .006).

CONCLUSIONS

Three-dimensional transvaginal sonography reveals differences in cervical volume and vascularization indices between pregnancies with an asymptomatic short cervix and cases with threatened preterm labor, although cervical length is similar in both groups.