Universal cervical length screening for singleton pregnancies with no history of preterm delivery, or the inverse of the Pareto principle

Asymptomatic short cervix and threatened preterm labor: A comparative study on perinatal outcomes

OBJECTIVE

To determine the rate of delivery within 15 days of admission among patients with an asymptomatic short cervix (ASC) compared to those admitted for threatened preterm labor (TPL).

MATERIAL AND METHODS

This retrospective study conducted in a tertiary maternity hospital, included patients with a singleton pregnancy admitted with a cervical length of less than 25 mm between 24 and 34 weeks. The population was divided into two groups, patients with ASC (i.e., with no contractions at admission) and patients with TPL. The primary outcome was the delivery rate within 15 days of admission. Secondary outcomes included gestational age at delivery, preterm delivery rate before 37°/7 weeks and before 34°/7 weeks, admission to delivery interval, 5 min Apgar score and transfer to neonatal intensive care unit rate. The characteristics of the two groups and the primary and secondary outcomes were compared between the two groups using univariate analysis. Two subgroup analysis were performed, one restricted to patients with a mildly modified CL (15 ≤ CL < 25 mm), and one excluding patients at high risk of preterm birth.

RESULTS

Among the 247 included patients, 136 (55.1 %) had TPL, and 111 (44.9 %) ASC. There were no significant differences in the rate of patient who delivered within 15 days of admission between the groups, 13.2 % in the TPL group vs 8.0 % in the ASC group (p = 0.22). Patients in the TPL group had a significantly higher frequency of delivery before 34 weeks compared to those in the ASC group (19.9 % versus 9.0 %, p = 0.02 This finding persisted in the subgroup analysis excluding patients at high risk of preterm birth (16.5 % in the TPL subgroup vs. 6.9 % in the ASC subgroup, p = 0.04). There were no significant differences in the rates of preterm delivery before 37 weeks, the admission-to-delivery interval, or neonatal outcomes between the two groups or within the subgroup analyses.

CONCLUSION

The frequency of delivery within 15 days of admission was not statistically different between patients with an asymptomatic short cervix and those with TPL. Nevertheless, these asymptomatic patients delivered significantly later and less frequently before 34 weeks, with only one in ten requiring corticosteroids.

Universal cervical length screening and risk of spontaneous preterm birth: a systematic review and meta-analysis

OBJECTIVE

To evaluate the risk of spontaneous preterm birth with or without universal transvaginal ultrasound cervical length screening at the time of midtrimester scan.

DATA SOURCES

Medline, Embase, ClinicalTrials.gov, and Web of Science were systematically searched from the inception of the databases to November 12, 2023, using combinations of the relevant medical subject heading terms, key words, and word variants that were considered suitable for the topic.

STUDY ELIGIBILITY CRITERIA

Studies including individuals with singleton gestations at 16-25 weeks of gestation screened or not screened with universal transvaginal ultrasound cervical length screening were considered eligible. Primary outcome was spontaneous preterm birth <37 weeks; secondary outcomes were spontaneous preterm birth <34 and <32 weeks.

METHODS

Random effect head-to-head analyses were used to directly compare each outcome, expressing the results as summary odds ratio and relative 95% confidence interval. The quality of the included studies was independently assessed by 2 reviewers, using the Newcastle-Ottawa scale for cohort studies and the Cochrane risk-of-bias tool for randomized controlled studies. The study was registered on the prospective register of systematic reviews database (PROSPERO) (registration number: CRD42022385325).

RESULTS

Eight studies, including 447,864 pregnancies, were included in the meta-analysis (213,064 screened with transvaginal ultrasound cervical length and 234,800 unscreened). In the overall analysis, universal transvaginal ultrasound cervical length did not significantly decrease the spontaneous preterm birth rates <37 weeks (odds ratio, 0.92 [95% confidence interval, 0.84-1.01], P=.07) and <34 weeks (odds ratio, 0.87 [95% confidence interval, 0.73-1.04], P=.12), but was significantly associated with a lower risk of spontaneous preterm birth <32 weeks (odds ratio, 0.84 [95% confidence interval, 0.76-0.94], P=.002). Individuals without a prior spontaneous preterm birth had a significantly lower risk of spontaneous preterm birth <37 weeks (odds ratio, 0.88 [95% confidence interval, 0.79-0.97], P=.01) and a lower trend of spontaneous preterm birth <32 weeks (odds ratio, 0.82 [95% confidence interval, 0.66-1.01], P=.06) when screened with transvaginal ultrasound cervical length, compared with no screening.

CONCLUSION

Universal transvaginal ultrasound cervical length screening usually <24 weeks in singletons without a prior spontaneous preterm birth, is associated with a significant reduction in spontaneous preterm birth <37 weeks, compared with no screening.

Arabin-pessary or McDonald Cerclage in Cervical Shortening?

OBJECTIVE

The aim of the present study is to compare the effectiveness of Arabin pessary and McDonald cervical cerclage on preterm delivery.

METHODS

 We conducted a retrospective analysis of data from patients who underwent either Arabin pessary or McDonald cerclage between January 1, 2019, and January 1, 2023. A total of 174 patients were included in the study, with 31 undergoing Arabin pessary and 143 receiving cervical cerclage using the McDonald technique in singleton pregnant women with cervical insufficiency, which applied between 14 and 22 gestational weeks. We included singleton pregnant women with normal morphology, and with normal combined test. The primary outcome was the impact of each method on preterm delivery (< 34 gestational weeks).

RESULTS

 The weeks of cervical cerclage or pessary application were compatible with each other (p < 0.680). The pessary group had a statistically significant longer time to delivery compared with the Cerclage group (cerclage group mean 30.8 c 7.1 standard deviation [SD] versus pessary group mean 35.1 ± 4.4 SD; p < 0.002). A statistically significant difference was found between the pessary and cerclage groups in terms of delivery at < 34 weeks (p = 0.002). In patients with cervical length between 25 and 15mm and < 15mm, no significant difference was found between the pessary and cerclage groups in terms of delivery week (p < 0.212; p < 0.149). Regardless of the technique applied, no statistically significant difference was observed between cervical length and birth < 34 weeks.

CONCLUSION

 Our study found that pessary use for cervical insufficiency is statistically more effective than cervical cerclage surgery in preventing preterm births < 34 weeks in singleton pregnancy.

Maternal and obstetrical factors associated with short cervical length at midtrimester in women with no history of preterm delivery

AIM

To evaluate associations between maternal characteristics and a short cervix in patients without history of preterm delivery, and to determine if these characteristics can predict the presence of a short cervix.

MATERIALS AND METHODS

This is a retrospective cohort study that included 18,592 women with singleton pregnancies without history of previous preterm deliveries who underwent universal transvaginal cervical length (TVCL) screening between 18 + 0 and 23 + 6 weeks/days of gestation. A short cervix was defined as a cervical length (CL) ≤25 mm, ≤20 mm, and ≤15 mm. Associations between maternal age, weight, height, body mass index (BMI), previous term deliveries, and history of previous miscarriages, with a short cervix were evaluated using logistic regression models.

RESULTS

The prevalence of a short cervix in our population was: CL ≤25 mm, 2.2% (n = 403); CL ≤20 mm, 1.2% (n = 224); and CL ≤15 mm, 0.9% (n = 161). Women with BMI >30 and/or previous abortions constituted 45.5% of the total population (8463/18,582). Significant associations with short cervix were observed for women with BMI ≥30, and for women with at least one previous abortion (p < .001). Parous women had a significantly lower association with a short cervix than nulliparous women (p < .001). Maternal age or height were not associated with a short cervix. Prediction of short cervix based on presence of any of the following: BMI ≥ 30 or previous abortions showed sensitivities of 55.8% (≤25 mm), 61.6% (≤20 mm), and 63.4% (≤15 mm) with similar specificity (50.1-54.6%) and likelihood ratio positive (1.2-1.5); and prediction based on BMI ≥ 30 and previous abortions showed sensitivities of 11.1% (≤25 mm), 14.7% (≤20 mm), and 16.7% (≤15 mm) with specificity 93%.

CONCLUSIONS

Among low risk women for spontaneous preterm delivery, those with a BMI ≥30 and/or previous miscarriages had a significantly increased risk for a short cervix at 18 + 0 and 23 + 6 weeks/days of gestation. Despite these significant associations, screening by maternal risk factors in a low risk population of pregnant women should not be an alternative to mid-trimester universal CL measurement.

Cytokine quantification and association with cervical length in a prospective cohort of pregnant women

BACKGROUND

Preterm birth is a leading cause of infant morbidity and mortality; its multifactorial causes are an obstacle to understanding etiology and pathogenesis. The importance of cytokines and inflammation in its etiology and association with the short cervix is nowadays well-proven. To date, there are no reliable biological or biochemical markers to predict preterm birth; even though the length of the cervix has high specificity, its sensitivity with the cervix below 2.5 cm is low.

OBJECTIVE

We study the association of plasma cytokine levels and cervical length in search of predictors of preterm birth.

STUDY DESIGN

We evaluated a total of 1400 pregnant women carrying a single fetus between 20 and 25 weeks of gestation, and 1370 of them after childbirth in a nested case-control study of a prenatal cohort. Eligible pregnant women were interviewed and submitted to obstetric morphological and transvaginal ultrasound with cervical length measurement, gynecological examination, and blood collection. Preterm birth occurred in 133 women, 129 included in the study, and a control group randomly selected at a 2:1 ratio. A total of 41 cytokines with a higher probability of being associated with preterm birth or being of significance during labor were determined.

RESULTS

Cytokine and cervical length analysis by multivariate analysis of the conditional interference tree revealed that growth-related oncogene values of less than 2293 pg/mL were significantly associated with a cervical length of less than 2.5 cm.

CONCLUSIONS

As well as a cervical length shorter than 2.5 cm, growth-related oncogene levels of less than 2293 pg/ml may be associated with an increased risk of PB. Analysis based on the association of biomarkers and of the interaction between cytokines is a promising pathway in search of a predictor of preterm birth.

Development of risk prediction models for preterm delivery in a rural setting in Ethiopia

Background

Preterm birth complications are the leading causes of death among children under five years. However, the inability to accurately identify pregnancies at high risk of preterm delivery is a key practical challenge, especially in resource-constrained settings with limited availability of biomarkers assessment.

Methods

We evaluated whether risk of preterm delivery can be predicted using available data from a pregnancy and birth cohort in Amhara region, Ethiopia. All participants were enrolled in the cohort between December 2018 and March 2020. The study outcome was preterm delivery, defined as any delivery occurring before week 37 of gestation regardless of vital status of the foetus or neonate. A range of sociodemographic, clinical, environmental, and pregnancy-related factors were considered as potential inputs. We used Cox and accelerated failure time models, alongside decision tree ensembles to predict risk of preterm delivery. We estimated model discrimination using the area-under-the-curve (AUC) and simulated the conditional distributions of cervical length (CL) and foetal fibronectin (FFN) to ascertain whether they could improve model performance.

Results

We included 2493 pregnancies; among them, 138 women were censored due to loss-to-follow-up before delivery. Overall, predictive performance of models was poor. The AUC was highest for the tree ensemble classifier (0.60, 95% confidence interval = 0.57-0.63). When models were calibrated so that 90% of women who experienced a preterm delivery were classified as high risk, at least 75% of those classified as high risk did not experience the outcome. The simulation of CL and FFN distributions did not significantly improve models' performance.

Conclusions

Prediction of preterm delivery remains a major challenge. In resource-limited settings, predicting high-risk deliveries would not only save lives, but also inform resource allocation. It may not be possible to accurately predict risk of preterm delivery without investing in novel technologies to identify genetic factors, immunological biomarkers, or the expression of specific proteins.

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.

The introduction of a universal transvaginal cervical length screening program is associated with a reduced preterm birth rate

BACKGROUND

Midtrimester sonographic short cervix is a good predictor of preterm birth in singleton pregnancies.

OBJECTIVE

This study aimed to assess the impact of implementing a universal transvaginal cervical length screening program on preterm birth rate.

STUDY DESIGN

This study consisted of 2 parts: a before-and-after multicenter study and a study on the ECHOCOL ("echo"="ultrasound" and "col"="cervix" in French) prospective cohort. We compared the rate of preterm birth before and after the introduction of universal cervical length screening at the time of midtrimester anatomy ultrasound. The multicenter before-and-after regional study included all women with a singleton pregnancy who gave birth after 24 weeks' gestation in the South East of France from January 1, 2012 to April 30, 2018. In parallel, the ECHOCOL cohort study was prospectively conducted from May 2015 to July 2018, including 17 maternity hospitals in the South East region of France. In case of asymptomatic short cervix <25 mm, treatments offered included 200 mg of vaginal progesterone, or cerclage, or a pessary until 34 weeks' gestation.

RESULTS

We observed a significant decrease rate of preterm birth between periods A and B after multivariate analysis. (respectively, 5.8% vs 5.6%; adjusted odds ratio, 0.92; 95% confidence interval, 0.89-0.95; P<.0001). In parallel, the percentage of cervical length screening significantly increased from 28.9% in period A to 52.9% in period B (odds ratio, 2.76; 95% confidence interval, 2.71-2.80; P<.0001). Among the 3468 patients of the ECHOCOL prospective cohort, 38 (1.1%) asymptomatic short cervices were detected, and 192 patients gave birth prematurely (11 with an asymptomatic short cervix and 181 without). In the ECHOCOL cohort, a marked but statistically insignificant tendency toward a reduced rate of preterm birth before 37 weeks of gestation was observed (from 5.8% to 5.5%; adjusted odds ratio, 0.72; 95% confidence interval, 0.51-1.03; P=.068).

CONCLUSION

This study showed a significantly lower rate of preterm birth after the implementation of a universal cervical length screening and treating policy during the second trimester of pregnancy. The clinical trial was registered under NCT02598323.

Implementing a Universal Cervical Length Screening Program in a Large Hospital System, it Takes Some Time to Achieve Consistent Results

OBJECTIVE

To describe changes in the acceptance of transvaginal (TV) cervical length (CL) measurements, and in the variance of CL measurements among operators, after implementation of universal TV-CL measurements at 18+0-23+6 weeks/days of gestation.

STUDY DESIGN

Retrospective cohort study Participants/Materials, Setting, Methods This study was performed after universal TV-CL screening was implemented at the University of Texas Health Science Center in Houston, Texas, for all women undergoing an anatomy ultrasound (US) between 18 0/6 and 23 6/7 weeks of gestation. Pregnant women carrying singletons without prior history of preterm delivery who underwent anatomy ultrasound evaluation between September 2017 and March 2020 (30 months) were included. The complete study period was divided in five epochs of six months each. Changes in patient's acceptance for the TV scan, in CL distribution, in the prevalence of short cervix defined as ≤15, ≤20, or ≤25 mm, and in the performance of ultrasound operators across the five epochs were evaluated. For this analysis, success rate was defined as the percentage of TV-CL measurements obtained in relation to the number of second trimester anatomy scans.

RESULTS

A total of 22,207 low risk pregnant women evaluated by 36 trained sonographers were analyzed. Overall, the acceptance for TV-CL measurement was 82.3% (18,289/22,207), increasing from 76.7% in the first epoch to 82.8% (p<0.0001) in the last epoch. The mean CL did not significantly change from 38.6 mm in the first epoch to 38.5 mm in the last epoch (p=0.7); however, the standard deviation decreased from 7.9 mm in the first epoch to 7.04 mm in the last epoch (p=<0.01). The prevalence of a short cervix ≤25 mm was 2.2% (n=399/18,289), ≤20 mm was 1.2% (224/18,289), and ≤15 mm was 0.9% (162/18,289). This prevalence varied only for CL ≤25 mm from 3.02% (88/2,907) in the first epoch to 1.77% (64/3,615) in the last epoch (p=0.0009). There was a variation in CL measurements among operators (mean 3.3 mm). Sonographers with less than one year of experience had a lower success rate for completing TV-CL examinations than more experienced sonographers (80.8% vs. 85.8%; p <0.03). In general 77% (27/35) of operators had a success rate ≥80% for completing TV-SL scans.

LIMITATIONS

Characteristics of individuals who accepted versus those who declined TV-CL were not compared; CL values were not correlated with clinical outcomes.

CONCLUSIONS

During the first six months after implementation of a universal cervical length screening program, there was greater variation in CL measurements, lower acceptance for a TV ultrasound, and a higher number of women diagnosed with a CL ≤25 mm, as compared to subsequent epochs. After the first six months, these metrics improved and remained stable. Most operators improved their performance over time; however, there were a few with a low success rate for TV-CL, and others who systematically over or under estimate CL measurements.

The perceptions of obstetric care providers about cervical length screening for preterm birth prevention

BACKGROUND

Routine cervical length (CL) measurement at the mid-pregnancy ultrasound is a central recommendation of the Western Australian Preterm Birth Prevention Initiative (Initiative).

AIM

To evaluate the perceptions and changes in practice of Western Australian obstetric care providers regarding routine CL screening for preterm birth (PTB) prevention following the Initiative introduction.

METHODS

Two self-administered questionnaires were completed by providers from a range of practices. The first was during site visits with the Initiative Outreach team in 2015-2016. The questionnaire was re-issued in 2021 via online dissemination. Participant demographic data and opinions on CL screening for PTB prevention were collected.

RESULTS

Two hundred and fourteen providers participated in 2015-2016 and 109 in 2021. In both surveys, providers were more likely to discuss transvaginal CL screening with high-risk women (48.1%, 76.1%; P < 0.001) compared with low-risk (7.5%, 18.3%; P = 0.002) and the importance of CL screening (13.5%, 40.4%; P < 0.001), in 2015-2016 and 2021, respectively. Responses relating to CL screening, including what constitutes a short cervix on ultrasound were varied. A transabdominal CL <35 mm was classified as short by 46.2% and 37.6% and <25 mm on transvaginal ultrasound by 49.1% and 64.2%, in the respective surveys. Most providers ceased progesterone (68.6%, 75.2%) at >28 weeks gestation.

CONCLUSIONS

Providers focused on women with overt PTB risk factors, rather than a universal CL screening approach. Although there was improvement between the surveys, the definition of what constitutes a short cervix on ultrasound and how to treat and monitor women with a short CL remained varied.

Prediction of Preterm Using Time Series Technology Based Machine Learning: Retrospective Cohort Study (Preprint)

Background

Objective

Methods

Results

Conclusions

Effects of prophylactic vaginal progesterone administration on mild cervical shortening (TROPICAL study): a multicenter, double-blind, randomized trial

Vaginal progesterone reduces the preterm birth frequency among high-risk women with a cervical length ≤25 mm at midtrimester. However, the strategy may promote no substantial reduction in overall preterm birth rates, because such high-risk women are only approximately 2% of all pregnant women, which restrict the number of participants. Our purpose was to determine whether prophylactic vaginal progesterone administration can preserve cervical length and reduce preterm birth rates among women with mild cervical shortening.This multicenter, parallel-arm, double-blind, randomized, placebo-controlled trial involved vaginal progesterone administration (200 mg daily from 16 to 33 weeks of gestation) among asymptomatic women with a singleton pregnancy and a sonographic cervical length of 25 to <30 mm between 16 and 23 weeks of gestation. The primary and secondary endpoints were cervical shortening rates at 34 weeks of gestation and preterm birth rates, respectively. The trial was registered at the University Hospital Medical Information Network (UMIN000013518) in Japan.Between April 2014 and March 2018, 119 women were randomly assigned to the progesterone group (n = 59) and the placebo group (n = 60). No significant differences in the frequency of women with a cervical length ≥20 mm at 34 weeks of gestation were observed between both groups. All preterm births occurred after 34 weeks of gestation, except for one patient in the placebo group. The progesterone group had a lower rate of preterm birth before 37 weeks than the placebo group (3.4% vs. 15.0%, respectively; p < .05).Despite having no effect on preserving cervical length, prophylactic vaginal progesterone administration reduced preterm birth frequency among women with mild cervical shortening. Our results are suggesting that women with mild cervical shortening are at risk for late preterm birth and the need for expanding progesterone treatment indications to include not only high-risk but also low-risk populations.

The influence of race on cervical length in pregnant women in Brazil

OBJECTIVES

Short cervical length is a predictor of preterm birth. We evaluated if there were racial differences in variables associated with cervical length in pregnant Brazilian women.

METHODS

Cervical length was determined by vaginal ultrasound in 414 women at 21 weeks gestation. All women were seen at the same clinic and analyzed by the same investigators. Women found to have a short cervix (≤25 mm) received vaginal progesterone throughout gestation. Composition of the vaginal microbiome was determined by analysis of the V1-V3 region of the gene coding for bacterial 16S ribosomal RNA. Demographic, clinical and outcome variables were determined by chart review. Subjects were 53.4% White, 37.2% mixed race and 9.4% Black.

RESULTS

Pregnancy, medical history and education level were similar in all groups. Mean cervical length was shorter in Black women (28.4 mm) than in White (32.4 mm) or mixed race (32.8 mm) women (p≤0.016) as was the percentage of women with a short cervix (23.1, 12.2, 7.8% in Black, White, mixed race respectively) (p≤0.026). Mean cervical length increased with maternal age in White (p=0.001) and mixed race (p=0.045) women but not Black women. There were no differences in bacterial dominance in the vaginal microbiota between groups. Most women with a short cervix delivered at term.

CONCLUSIONS

We conclude that Black women in Brazil have a shorter cervical length than White or mixed race women independent of maternal age, pregnancy and demographic history or composition of the vaginal microbiome.

It is about time. The advantage of transabdominal cervical length screening

PURPOSE

Sonographic cervical length (CL) measurement has become a standard practice for identifying women at increased risk for preterm birth. We aimed to assess the time needed for CL measurement during fetal anatomy scan using either transabdominal or transvaginal ultrasound, and to provide a predictive value of the transabdominal CL measurements for reassuring transvaginal CL measurements of more than 25 mm.

METHODS

In a prospective study we measured CL transabdominally, and transvaginally in all the anatomy scans performed at 18-25 weeks' gestation, from January 2017 until January 2018. CL and the duration of the examination were compared between the two approaches. Adjustments were made for, body mass index, previous cesarean sections and parity.

RESULTS

Four hundred sixty-eight patients participated in the study. The time needed for the transabdominal CL measurement was significantly lower compare with the transvaginal CL measurement (0.46 ± 0.3 min versus 6.9 ± 1.38 min, p < 0.001). The CL measured transabdominally was significantly shorter than the CL measured transvaginally (36.7 ± 6.7 mm versus 41.9 ± 7.3 mm, respectively p < 0.001). All women with transabdominal CL measurements above 36 mm (64.2% of patients) had a transvaginal CL of more than 25 mm.

CONCLUSION

Transvaginal measurement of CL is a time-consuming procedure that prolong fetal anomaly scan by 25%. Transabdominal CL measurement of 36 mm is reassuring CL above 25 mm. Transabdominal ultrasound should be used as an initial tool for CL screening. Transvaginal measurements of CL should be reserved for high-risk women, for women with difficulties in demonstrating the cervix abdominally, and for women with transabdominal measurements of less than 36 mm.

Controversies in the prevention of spontaneous preterm birth in asymptomatic women: an evidence summary and expert opinion

Preterm birth prevention is multifaceted and produces many nuanced questions. This review addresses six important clinical questions about preterm birth prevention as voted for by members of the UK Preterm Clinical Network. The questions cover the following areas: preterm birth prevention in 'low-risk' populations; screening for asymptomatic genital tract infection in women at high risk of preterm birth; cervical length screening with cerclage or vaginal pessary in situ; cervical shortening whilst using progesterone; use of vaginal progesterone in combination with cervical cerclage; and optimal advice about intercourse for women at high risk of preterm birth.

The Impact of Previous Obstetric History on the Risk of Spontaneous Preterm Birth in Women with a Sonographic Short Cervix

OBJECTIVE

The natural history of women with a short cervix and a low-risk obstetric history remains poorly defined. In our study, we sought to better characterize the impact of previous obstetric history on the delivery outcomes in women diagnosed with a mid-trimester sonographic short cervix.

STUDY DESIGN

We performed a retrospective cohort study of women with singleton gestations who underwent transvaginal cervical length screening between 16 and 24 weeks at two urban hospitals in Philadelphia between January 2013 and March 2018 and were found to have a short cervix (defined as ≤2 cm). Women were excluded from the cohort if there were major fetal anomalies noted or if delivery outcome information was not available. The cohort was then divided into three groups based on obstetric history: nulliparous, history of full-term birth only, or history of spontaneous preterm birth (sPTB). The primary outcome was sPTB <37 weeks, while the secondary outcome was sPTB <34 weeks.

RESULTS

Our cohort included a total of 384 singleton pregnancies that were diagnosed with a sonographic short cervix: 165 women were nulliparous, 119 women had a history of full-term birth, and 100 women with a history of sPTB. We found that women with a short sonographic cervix had a sPTB rate of 39.6% with no differences found between the three groups. Only two-thirds of nulliparous women and women with a history of full-term birth received the recommended preventative treatment, compared with almost 100% of women with a history of sPTB.

CONCLUSION

Women with and without a history of sPTB are at comparable risk of sPTB in the presence of a sonographically short cervix. Preventative therapies should be recommended to both nulliparous women and women with a history of full-term birth since uptake in this population are not as high.

Progesterone and preterm birth

Progestogens (vaginal progesterone and intramuscular 17-hydroxyprogesterone acetate) are widely recommended for women at high risk of preterm birth. Typical regimens include 17-hydroxyprogesterone caproate (250 mg intramuscularly weekly), starting at 16-20 gestational weeks until 36 weeks or delivery for women with a singleton gestation and a history of spontaneous preterm birth, or vaginal progesterone (90-mg vaginal gel or 200-mg micronized vaginal soft capsules) for women with a short cervix (typically ≤25 mm). Although some randomized trials support this approach, neither of the largest trials (PROLONG for 17-hydroxyprogesterone acetate or OPPTIMUM for vaginal progesterone) demonstrated efficacy. There are almost no data on long-term effects, and none that shows benefit beyond the neonatal period. Although some analyses suggest the cost-effectiveness of the approach, a cervical length screening program followed by progesterone for those with a short cervix will reduce preterm birth rates by less than 0.5%. The present review assesses evidence on the efficacy, likely impact, and long-term effects of implementing the recommendations for progestogens in full. Clinicians and pregnant women can look forward to resolution of the conflicting views on efficacy once the Patient-Centered Outcomes Research Initiative (PCORI)-funded individual patient data meta-analysis is published.

Predictive Value of Midtrimester Universal Cervical Length Screening Based on Parity

OBJECTIVES

To evaluate the effect of parity on performance characteristics of midtrimester cervical length (CL) in predicting spontaneous preterm birth (sPTB) before 37 weeks.

METHODS

This was a retrospective cohort study of 13,508 women with no history of sPTB undergoing universal transvaginal CL screening at 17 to 23 weeks' gestation from 2011 to 2016. Patients who declined screening or with unknown delivery outcomes were excluded. Areas under the receiver operator characteristic curves were used to assess and compare the predictive ability of CL screening for sPTB. The sensitivity, specificity, and positive and negative predictive values were estimated for specific CL cutoffs for prediction of sPTB.

RESULTS

There were 20,100 patients, of whom 2087 (10%) declined screening and 4505 (22%) did not meet inclusion criteria. Of the remaining 13,508 patients, 43% were nulliparous. The incidence rates of sPTB were 6.5% in nulliparas and 4.9% in multiparas (P < .001). The mean CLs were 39.9 mm in nulliparas and 41.8 mm in multiparas (P < .001), and those of the first percentiles were 19.0 mm in nulliparas and 24.0 mm in multiparas. Cervical length was significantly more predictive of sPTB in nulliparas (area under the curve, 0.67; 95% confidence interval, 0.63-0.70; versus 0.61, 95% confidence interval, 0.57-0.63; P = .008). At CL cutoffs of 10, 15, 20, and 25 mm or less, the sensitivity was lower in multiparas, and the specificity was comparable between the groups.

CONCLUSIONS

Midtrimester CL is less predictive of sPTB in multiparas compared to nulliparas. The poor predictive ability, especially in multiparas, calls into question the value of universal CL screening in this population.

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.

Use of progesterone supplement therapy for prevention of preterm birth: review of literatures

Preterm birth (PTB) is one of the most common complications during pregnancy and it primarily accounts for neonatal mortality and numerous morbidities including long-term sequelae including cerebral palsy and developmental disability. The most effective treatment of PTB is prediction and prevention of its risks. Risk factors of PTB include history of PTB, short cervical length (CL), multiple pregnancies, ethnicity, smoking, uterine anomaly and history of curettage or cervical conization. Among these risk factors, history of PTB, and short CL are the most important predictive factors. Progesterone supplement therapy is one of the few proven effective methods to prevent PTB in women with history of spontaneous PTB and in women with short CL. There are 2 types of progesterone therapy currently used for prevention of PTB: weekly intramuscular injection of 17-alpha hydroxyprogesterone caproate and daily administration of natural micronized progesterone vaginal gel, vaginal suppository, or oral capsule. However, the efficacy of progesterone therapy to prevent PTB may vary depending on the administration route, form, dose of progesterone and indications for the treatment. This review aims to summarize the efficacy and safety of progesterone supplement therapy on prevention of PTB according to different indication, type, route, and dose of progesterone, based on the results of recent randomized trials and meta-analysis.

Recent advances in the prevention of preterm birth

Preterm birth (PTB) remains a major obstetric healthcare problem and a significant contributor to perinatal morbidity, mortality, and long-term disability. Over the past few decades, the perinatal outcomes of preterm neonates have improved markedly through research and advances in neonatal care, whereas rates of spontaneous PTB have essentially remained static. However, research into causal pathways and new diagnostic and treatment modalities is now bearing fruit and translational initiatives are beginning to impact upon PTB rates. Successful PTB prevention requires a multifaceted approach, combining public health and educational programs, lifestyle modification, access to/optimisation of obstetric healthcare, effective prediction and diagnostic modalities, and the application of effective, targeted interventions. Progress has been made in some of these areas, although there remain areas of controversy and uncertainty. Attention is now being directed to areas where greater gains can be achieved. In this mini-review, we will briefly and selectively review a range of PTB prevention strategies and initiatives where progress has been made and where exciting opportunities await exploitation, evaluation, and implementation.