Does cervical length at 13-15 weeks' gestation predict preterm delivery in an unselected population?

First-trimester and early-second-trimester transvaginal cervical length before 16 weeks among women with preterm and term birth: a systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the differences in first-trimester and early-second-trimester transvaginal cervical length between patients with spontaneous preterm birth and those with term birth.

DATA SOURCES

PubMed, MEDLINE, Embase, and the Cochrane Library were systematically searched through August 2023.

STUDY ELIGIBILITY CRITERIA

Studies had to include (1) transvaginal cervical length measurement before 16+0 weeks of gestation and (2) transvaginal cervical length measurement in a population of patients who delivered preterm and at term. Abstracts, studies with duplicated data, and those with cervical length measured by transabdominal ultrasound scan were excluded.

METHODS

K.W.C. and J.L. searched for, screened, and reviewed the articles independently. The quality of the studies was assessed using the Newcastle-Ottawa scale. Mean differences were calculated using a random-effects model and pooled through a meta-analysis.

RESULTS

A total of 5727 published articles were identified. Only 10 studies (which analyzed 22,151 pregnancies) met the inclusion criteria. All studies excluded iatrogenic preterm birth. Transvaginal cervical length was significantly shorter in women with spontaneous preterm birth than in those who delivered at term (mean difference, -0.97; 95% confidence interval, -1.65 to -0.29; P=.005; I2=69%). When a linear technique was used to measure transvaginal cervical length, a significantly shorter transvaginal cervical length was associated with spontaneous preterm birth as opposed to term birth (mean difference, -1.09; 95% confidence interval, -1.96 to -0.21; P=.02; I2=77%). A shorter transvaginal cervical length measured by other techniques was also associated with spontaneous preterm birth before 34 to 35 weeks (mean difference, -1.87; 95% confidence interval, -3.04 to -0.70; P=.002; I2=0%). When studies where interventions were given for a "short" cervix or studies with a mean transvaginal cervical length ≥40 mm were excluded, a significantly shorter transvaginal cervical length was observed among those with spontaneous preterm birth (mean difference, -1.13; 95% confidence interval, -1.89 to -0.37; P=.004; mean difference, -0.86; 95% confidence interval, -1.67 to -0.04; P=.04; respectively). The optimal transvaginal cervical length cutoff was 38 to 39 mm, yielding pooled sensitivity of 0.80, specificity of 0.45, positive likelihood ratio of 1.16, negative likelihood ratio of 0.33, diagnostic odds ratio of 5.12, and an area under the curve of 0.75.

CONCLUSION

Women with spontaneous preterm birth had significantly shorter transvaginal cervical length before 16 weeks of gestation compared with those who delivered at term. The linear method and the 2-line method are acceptable techniques for measuring transvaginal cervical length.

Machine Learning-Based Prediction Model of Preterm Birth Using Electronic Health Record

Objective

Preterm birth (PTB) was one of the leading causes of neonatal death. Predicting PTB in the first trimester and second trimester will help improve pregnancy outcomes. The aim of this study is to propose a prediction model based on machine learning algorithms for PTB.

Method

Data for this study were reviewed from 2008 to 2018, and all the participants included were selected from a hospital in China. Six algorisms, including Naive Bayesian (NBM), support vector machine (SVM), random forest tree (RF), artificial neural networks (ANN), K-means, and logistic regression, were used to predict PTB. The receiver operating characteristic curve (ROC), accuracy, sensitivity, and specificity were used to assess the performance of the model.

Results

A total of 9550 pregnant women were included in the study, of which 4775 women had PTB. A total of 4775 people were randomly selected as controls. Based on 27 weeks of gestation, the area under the curve (AUC) and the accuracy of the RF model were the highest compared with other algorithms (accuracy: 0.816; AUC = 0.885, 95% confidence interval (CI): 0.873–0.897). Meanwhile, there was positive association between the accuracy and AUC of the RF model and gestational age. Age, magnesium, fundal height, serum inorganic phosphorus, mean platelet volume, waist size, total cholesterol, triglycerides, globulins, and total bilirubin were the main influence factors of PTB.

Conclusion

The results indicated that the prediction model based on the RF algorithm had a potential value to predict preterm birth in the early stage of pregnancy. The important analysis of the RF model suggested that intervention for main factors of PTB in the early stages of pregnancy would reduce the risk of PTB.

Prediction of spontaneous preterm birth by cervical length in the first trimester of pregnancy: Comparison of two measurement methods

INTRODUCTION

Our objectives were to compare the single-line and two-line methods of cervical length measurement in the first trimester of pregnancy and to evaluate the potential value of the first trimester cervical length measured by the two methods in predicting spontaneous preterm birth.

MATERIAL AND METHODS

This was a prospective study in singleton pregnancies at 11+0 to 13+6  weeks of gestation. Cervical length was measured by two methods: (i) a linear distance between the two ends of the glandular area around the endocervical canal (single-line method) and (ii) a sum of a linear distance from the internal os to the greatest cervical curvature and a linear distance from this point of the cervix to the external os (two-line method). The screening performance of the first trimester cervical length measured by the two different methods for the prediction of spontaneous preterm delivery was assessed by receiver-operating characteristics (ROC) curve analysis. The areas under the ROC (AUROC) were compared by De Long test.

RESULTS

A total of 1484 consecutive singleton pregnancies were included in this study. Spontaneous preterm delivery at <37 and <32 weeks occurred in 75 cases (5.1%) and 12 cases (0.8%), respectively. The median cervical length measured by the single-line method was significantly shorter than that by the two-line method (33.5 vs 36.5 mm, p < .001). Compared with the term delivery group, the median cervical length measured by the two-line method was shorter in women with spontaneous delivery at <32 weeks of gestation (36.5 vs 33.6 mm, p < .01). No significant difference in the median cervical length measured by the single-line method was detected between the spontaneous preterm delivery and term delivery groups. Receiver-operating-characteristic curves demonstrated that cervical length measured by the two-line method achieved better performance in predicting spontaneous delivery at <32 weeks compared with the single-line method (AUROC: 0.72 vs 0.61, p < .01).

CONCLUSIONS

We have demonstrated that the first trimester cervical length, measured by the two-line approach, holds promise as a potential screening tool for early spontaneous preterm delivery.

Nomogram to predict the risk of preterm birth before 37 weeks and 34 weeks in pregnant women with a short cervix

OBJECTIVES

This study investigated the potential factors that predict the risk of preterm birth (PTB) in pregnancies with a short cervix. These factors were used to create nomogram, which might be highly sensitive tools to predict the incidence of PTB.

METHODS

This retrospective cohort study enrolled pregnancies with a short cervix from 1 January 2017 to 1 January 2018. The primary outcomes were preterm birth <37 and 34 weeks. Logistic regression model was used to identify potential predictors of PTB. The identified risk factors were used to establish nomograms, which were validated using the receiver operating characteristic (ROC) curve and calibration curve.

RESULTS

In the multivariate analysis, overweight or obesity, parity ≧3 times, twin pregnancy, in vitro fertilization and embryo transfer (IVF-ET), gestational age at first observation of short cervix, cervical length (CL) at first observation of short cervix, history of PTB, and autoimmune disease were found to be predictors of PTB <37 weeks, while twin pregnancy, gestational age at first observation of short cervix, CL of short cervix, history of PTB, and prepregnancy hypertension were predictors of PTB <34 weeks. The area under the ROC curve of the nomogram predicting PTB <37 weeks and PTB <34 weeks were 0.803 and 0.771, respectively. Both models showed good discrimination.

CONCLUSIONS

Gestational age at first observation of short cervix, CL of short cervix and other factors are strong predictors of PTB in pregnancies with a short cervix. Both nomograms showed good discrimination and calibration, and hence might be effective in predicting PTB for this population.

Associations of temporal changes in cervical length and lower uterine segment length with spontaneous preterm delivery risk: a prospective study of 727 Japanese women

PURPOSE

A prospective assessment of the risk of spontaneous preterm delivery (sPTD) by evaluating temporal changes in cervical measurements.

METHODS

We analyzed clinical variables, focusing on cervical length (CL) and lower uterine segment (LUS) length (LUSL) as measured by transvaginal ultrasonography in 727 pregnant Japanese women.

RESULTS

In women undergoing term deliveries, CL increased from gestational week (GW) 8-25. In contrast, the combination of CL and LUSL (ComL for "combined length") gradually decreased and sole LUSL became almost 0 mm by GW 25. Univariate logistic regression analysis suggested that a history of PTD was a risk factor for sPTD. CL, LUSL, and ComL were not significant predictors of sPTD.

CONCLUSION

To assess the risk of sPTD in the second trimester, it is not necessary to distinguish the cervix from the LUS.

The first-trimester of pregnancy - A window of opportunity for prediction and prevention of pregnancy complications and future life

The International Federation of Gynecology and Obstetrics (FIGO) has identified non communicable maternal diseases (NCDs) as a new focus area. NCDs and exposures as related to pregnancy complications and later impairment of maternal and offspring health will form the basis for action in the forthcoming years. This paper summarizes recent advances, centered on the use of first-trimester testing, as a window of opportunity to predict and prevent many pregnancy complications; and for potential future prevention of NCDs in mother and offspring. Recent results from a large-scale randomized control trial have provided definitive proof that effective screening for preterm preeclampsia (preterm-PE), requiring delivery before 37 weeks' gestation, can be achieved with a combined test of maternal factors and biomarkers at 11-13 weeks and that aspirin, given to high-risk women, is effective in reducing the risk of preterm-PE and the length of stay in neonatal intensive care unit. This is the first successful example to illustrate that pregnancy complications is predictable and preventable in early pregnancy. Similar prediction and prevention strategies are being developed for hyperglycemia in pregnancy and preterm birth, with the intention for longer lasting interventions leading to significant downstream impact in improving long-term health in both mothers and babies.

Reference ranges for the uterine arteries Doppler and cervical length measurement at 11-13(+6) weeks of gestation in a Brazilian population

OBJECTIVE

To establish references ranges for the uterine arteries (UtA) Doppler and cervical length (CL) measurements at 11-13(+6) weeks of gestation in a Brazilian population.

METHODS

We performed a retrospective cross-sectional study with singleton low-risk pregnant women who underwent first trimester ultrasound exams of fetuses with crown-rump length (CRL) ranging from 45 to 84 mm. The mean UtA Doppler and CL measurements were performed by transvaginal route. The mean pulsatility index (PI) of uterine arteries was obtained with color Doppler at the level of cervico-corporeal junction. The CL was obtained in a sagittal view using the cervical gland area as landmark. We determined mean ± standard deviation (SD), ranges for mean PI of UtA and CL in each gestational age. Polynomial regression was performed to establish reference values.

RESULTS

We have assessed 598 first-trimester pregnancies: the CL measurement was obtained from 497, while the mean PI UtA Doppler was available in 450 pregnant women. The mean CL ranged from 33.41 to 35.58 mm while the PI UtA Doppler ranged from 1.89 to 1.45. The best fit curves were: CL = 30.790 + 0.057 × CRL and UtA PI = 2.411-0.011 × CRL.

CONCLUSION

References ranges for the mean UtA PI Doppler and CL measurement at 11-13(+6) weeks of gestation in a Brazilian population were established.

Transvaginal sonographic evaluation of cervical length in the second trimester of asymptomatic singleton pregnancies, and the risk of preterm delivery

OBJECTIVE

To evaluate cervical length in asymptomatic women with singleton pregnancies in the second trimester by means of transvaginal ultrasonography, and to examine the relation between cervical length and spontaneous preterm delivery.

DESIGN

Observational, prospective study.

SETTING

A university hospital and a county hospital in Western Sweden.

POPULATION

A total of 2122 asymptomatic women with live singleton pregnancies without fetal anomalies.

METHODS

Cervical length was measured at between 16 and 23 weeks of gestation by means of transvaginal ultrasonography. Data were analysed using logistic regression analysis.

MAIN OUTCOME MEASURES

Cervical length in relation to spontaneous preterm delivery <34 weeks (primary outcome) and <37 weeks of gestation (secondary outcome).

RESULTS

Eleven women had a cervical length of ≤25 mm (0.5%) and 73 women had a cervical length of ≤30 mm (3.4%). Spontaneous preterm delivery at <34 weeks occurred in 22/2061 women (1.1%) and at <37 weeks in 87/2061 women (4.2%). There was a significant association between cervical length and spontaneous preterm delivery at <34 weeks (odds ratio 1.78; 95% confidence interval 1.19-2.65 for a decrease of cervical length by 5 mm) but no significant association at <37 weeks.

CONCLUSIONS

The rate of short cervical length of ≤25 mm was lower than expected. The study confirmed the increased risk of spontaneous preterm delivery in women with a short cervix, although the analysis was based on only a few cases. In Sweden, a larger study is needed to evaluate the prevalence of short cervical length and the possible association with preterm delivery before universal screening can be recommended.

Prediction of spontaneous preterm delivery in singleton pregnancies: where are we and where are we going? A review of literature

Prematurity is the chief cause of neonatal morbidity and mortality. The objective of this study is to review the different methods for predicting preterm delivery in asymptomatic pregnant women and in situations of threatened preterm delivery. A search of the PubMed/Medline database was carried out for the years 1980-2012. We included studies for predicting preterm birth in asymptomatic and symptomatic patients. Models for predicting preterm delivery based on maternal factors, cervical length and obstetric history in first trimester of pregnancy is a valuable avenue of research. Nevertheless, prediction accuracy still needs to be improved. In the second and third trimesters, routine digital vaginal examination is of no value in asymptomatic women. Echography of the cervix is not useful except in patients with a history of late miscarriage or preterm delivery in order to offer them a preventive treatment. In symptomatic women, the combination of digital vaginal examination, cervical echography and fibronectin gives the best predictive results. Electromyography of the uterus and elastography of the cervix are interesting avenues for future research. Identifying patients at risk of preterm delivery should be considered differently at each stage of pregnancy.

Is there a role for cervical assessment and uterine artery Doppler in the first trimester of pregnancy as a screening test for spontaneous preterm delivery?

OBJECTIVE

To evaluate the role of cervical length (CL) and uterine artery pulsatility index (UtA-PI) at 11+0 to 13+6 weeks as predictors of spontaneous preterm delivery (sPTD) in a Chilean population.

METHODS

This was a prospective study of asymptomatic women with singleton pregnancies attending for a nuchal translucency scan at 11+0 to 13+6 weeks' gestation and who underwent a transvaginal scan for evaluation of CL and UtA-PI. Exclusion criteria were fetal and pregnancy complications (other than sPTD) and iatrogenic delivery at<34 weeks. Measurements of CL and UtA-PI were adjusted for fetal crown-rump length and maternal characteristics and expressed as multiples of the median (MoM) of the unaffected group. Prediction of sPTD using maternal and pregnancy characteristics was studied using logistic regression analysis.

RESULTS

A total of 3480 women were recruited into the study and, after application of exclusion criteria, 3310 were included in the analysis. The rate of sPTD at<34 weeks was 0.9% (n=31). A previous PTD had occurred in 7.4% of parous women. Patients with sPTD in the index pregnancy were characterized by a significantly higher prevalence of previous PTD (12.9% vs 3.7%, P<0.05). No significant difference was found in either CL or UtA-PI between pregnancies with and without subsequent sPTD. Logistic regression analysis showed that smoking and previous PTD were significantly associated with sPTD at<34 weeks. The combination of these characteristics provided a detection rate of 26% with a false-positive rate of 8%.

CONCLUSIONS

Neither UtA-PI nor CL during the first trimester was shown to be a useful predictor of early sPTD. However, a combined model that includes smoking and previous PTD predicts approximately one-quarter of those women destined to deliver at<34 weeks, with a false-positive rate of 8%.

Opening of the uterine isthmus at 11-13 weeks' gestation is not related to developmental abnormalities of the placenta

OBJECTIVES

To clarify whether openning of the uterine isthmus between 11 and 13weeks' gestation adversely affects the placental development.

METHODS

The uterine cervix and isthmus lengths were measured prospectively using transabdominal ultrasound at 11 to 13+6 weeks' gestation. Following delivery, the pregnancy and delivery course were reviewed. The associations between the conditions of the uterine isthmus during the first trimester and the perinatal complications associated with placental abnormalities were analyzed.

RESULTS

A total of 653 cases were analyzed. The isthmus had been completely opened (isthmus length = 0mm) in 15.9%, 21.6% and 24.1% of the cases at 11, 12 and 13 weeks' gestation. The frequencies of perinatal complications in the cases whose isthmus had been opened (cases) and the other cases (controls) were as follows; 1.4% and 1.0% (ns) for placenta previa, 1.4% and 1.2% (ns) for abnormal cord insertion, 3.5% and 4.3% (ns) for pre-eclampsia, 9.9% and 9.0% (ns) for small for gestational age, and 12.0% and 7.6% (ns) for preterm delivery, respectively.

CONCLUSION

Early opening of the uterine isthmus at 11 to 13 weeks' gestation does not appear to adversely affect either the placental development or the course of pregnancy.

What is predictive of preterm delivery in the first trimester: isthmus or cervical length?

OBJECTIVE

This study aims to evaluate the utility of first trimester cervical ultrasonography in predicting preterm delivery by separate analysis of measurements of cervical and isthmus length.

METHODS

This is a cohort study based on data collected prospectively on singletons between 1 July 2011 and 1 February 2013. Mean cervical, isthmus and cervico-isthmic complex length were measured for deliveries before and after 37 weeks.

RESULTS

A total of 1494 pregnancies were analysed, including 51 cases of spontaneous preterm delivery (3.4%). The cervico-isthmic complex in the first trimester was significantly shorter in patients who delivered before term (43.8 mm vs 47.5 mm, p = 0.04). This difference is related to differences in length at the isthmus (10.7 mm vs 14.1 mm, p = 0.005) rather than at the cervix proper (34.5 mm vs 35.0 mm, p = 0.56).

CONCLUSIONS

Measurement of the cervico-isthmic complex enables detection of a number of patients who will go on to deliver before term. Further studies are necessary to confirm that isthmic length and not cervical length is predictive of preterm delivery.

Transvaginal sonographic evaluation of the cervix in asymptomatic singleton pregnancy and management options in short cervix

Preterm delivery (PTD), defined as birth before 37 completed weeks of gestation, is the leading cause of perinatal morbidity and mortality. Evaluation of the cervical morphology and biometry with transvaginal ultrasonography at 16–24 weeks of gestation is a useful tool to predict the risk of preterm birth in low- and high-risk singleton pregnancies. For instance, a sonographic cervical length (CL) > 30 mm and present cervical gland area have a 96-97% negative predictive value for preterm delivery at <37 weeks. Available evidence supports the use of progesterone to women with cervical length ≤25 mm, irrespective of other risk factors. In women with prior spontaneous PTD with asymptomatic cervical shortening (CL ≤ 25 mm), prophylactic cerclage procedure must be performed and weekly to every two weeks follow-up is essential. This article reviews the evidence in support of the clinical introduction of transvaginal sonography for both the prediction and management of spontaneous preterm labour.

Prediction of preterm birth using the cervical consistency index

OBJECTIVES

To assess the diagnostic power of a new cervical consistency index (CCI) obtained using transvaginal sonography for the prediction of spontaneous preterm birth (PTB) and to establish reference ranges for this new variable.

METHODS

Included in this prospective cross-sectional study were 1115 singleton pregnancies at 5-36 weeks of gestation. Anteroposterior cervical diameter was measured before (AP) and after (AP') application of pressure on the cervix using the transvaginal probe. The index was calculated using the formula: CCI=((AP'/AP) × 100). Cervical length was also measured. The outcomes evaluated were spontaneous PTB before 32, 34 and 37 weeks. Logistic regression and analysis of receiver-operating characteristics (ROC) curves were performed to evaluate the diagnostic power of CCI and cervical length (adjusted for gestational age). Intraclass correlation coefficients (ICCs) and Bland-Altman analysis were used to evaluate intra- and interobserver variability.

RESULTS

In the 1031 women with follow-up, the rate of spontaneous PTB before 32 weeks was 0.87%, before 34 weeks was 2.13% and before 37 weeks was 7.76% (n=80). There were 31 (3.01%) iatrogenic PTBs before 37 weeks. An inverse linear correlation between gestational age and CCI was observed, with regression equation: CCI (in %)=89.8 - 1.35 × (GA in weeks); r(2)=0.66, P<0.001. Cervical length showed an inverse quadratic, though non-significant, relationship with gestational age: CL (in mm)=31.084 - 0.0278× (GA in weeks)(2) + 1.0772× (GA in weeks); r(2)=0.076, P<0.14. The intra- and interobserver ICCs for CCI were 0.99 (95% CI, 0.988-0.994) and 0.98 (95% CI, 0.973-0.987), respectively. The area under the ROC curve for CCI in the prediction of spontaneous PTB before 32 weeks was 0.947, for spontaneous PTB before 34 weeks it was 0.943 and for spontaneous PTB before 37 weeks it was 0.907. For a 5% screen-positive rate, CCI had a sensitivity of 67%, 64% and 45% for prediction of spontaneous PTB before 32, 34 and 37 weeks, respectively, with equivalent values of 11%, 9% and 11% for cervical length.

CONCLUSIONS

CCI shows a clear inverse linear relationship with GA. Assessment of CCI is reproducible and is effective in the prediction of spontaneous PTB. This new variable appears to provide better prediction of spontaneous PTB than does cervical length.

Cervical length changes from the first to second trimester of pregnancy, and prediction of preterm birth by first-trimester sonographic cervical measurement

OBJECTIVES

The purpose of this study was to examine the evolution of cervical length from the first to second trimester of pregnancy and the value of first-trimester cervical measurement in the prediction of preterm delivery.

METHODS

We conducted a longitudinal prospective study. Cervical length was measured by transvaginal sonography at 11 to 14 weeks (Cx1), 16 to 19 weeks (Cx2), and 20 to 24 weeks (Cx3).

RESULTS

Eight hundred singleton pregnancies were studied. The median cervical lengths were 33 mm for Cx1 and 31 mm for Cx2 and Cx3. Significant independent predictors for cervical length were maternal weight, height, and history of cervical surgery for Cx1, maternal height, history of cervical surgery, and history of preterm delivery for Cx2, and history of cervical surgery, history of first-trimester miscarriage, and history of spontaneous preterm delivery for Cx3. Mean cervical length shortening was 2.36 mm between Cx1 and Cx3. In the subgroups of women with previous cervical surgery and history of previous preterm birth, cervical shortening was significantly more prominent. The median Cx1 was significantly shorter in the women who subsequently delivered preterm; Cx1 predicted preterm delivery before 34 weeks (odds ratio, 0.746; 95% confidence interval, 0.649-0.869) and preterm delivery before 32 weeks (odds ratio, 0.734; 95% confidence interval, 0.637-0.912).

CONCLUSIONS

Cervical length in the first trimester depends on maternal characteristics and a history of cervical surgery. The cervix exhibits minimal changes from 11 to 24 weeks for most women, although the shortening is more prominent in women with a history of cervical surgery or preterm delivery. First-trimester cervical length measurement can predict preterm delivery.

Prediction of spontaneous preterm delivery from endocervical length at 11 to 13 weeks

OBJECTIVE

To define the potential value of endocervical length at 11 to 13 weeks' gestation in the prediction of spontaneous early delivery.

METHOD

The lengths of the endocervix and cervico-isthmic complex were measured by transvaginal ultrasound at 11 to 13 weeks in singleton pregnancies, including 1492 that subsequently delivered after 34 weeks and 16 (1.1%) who had spontaneous delivery before 34 weeks. In 1320 of the cases, the measurements were repeated at 20 to 24 weeks.

RESULTS

There were significant associations in the length of the endocervix and cervico-isthmic complex between 11 to 13 and 20 to 24 weeks (r = 0.548, p < 0.0001 and r = 0.194, p < 0.0001), and the respective median lengths were 32.4 and 32.2 mm for the endocervix and 45.3 and 40.4 mm for the cervico-isthmic complex. At 11 to 13 weeks in the early delivery group, compared to unaffected pregnancies, the median endocervical length was shorter (27.5 vs 32.5 mm, p < 0.0001), but there was no significant difference in the length of the cervico-isthmic complex (41.4 vs 45.4 mm, p = 0.054).

CONCLUSION

In the measurement of cervical length, the endocervix should be distinguished from the isthmus. The endocervical length at 11 to 13 weeks is shorter in pregnancies resulting in spontaneous delivery before 34 weeks than in those delivering after 34 weeks.

The role of cervical length measurement at 11-14 weeks for the prediction of preterm delivery

OBJECTIVE

To determine whether cervical length (CL) measurement at 11?14 weeks is predictive of preterm delivery (PTD).

METHODS

This was a prospective study of a low-risk population of 1113 women, who underwent CL measurement at 11-14 weeks. Mean CL was calculated for deliveries at >37, <37 and <34 weeks. Cut-off limits of 27 mm and 30 mm were used to examine the predictive value of CL.

RESULTS

Mean +/- SD CL for the entire study population was 40.6 +/- 5.5 mm. CL was analyzed for term and PTD (<37 weeks) and further analyzed for deliveries at 34-37 and <34 weeks. Mean CL was 38.9 +/- 5.5 mm for PTD and 40.8 +/- 5.5 mm for deliveries >37 weeks (p=0.001). Receiver operating characteristic analysis showed small predictive value of CL for PTD <37 weeks (sensitivity = 63.3% and specificity = 51.1%, area under the curve (AUC)=0.60, 95% CI: 0.54-0.66) (p=0.001) and did not show any predictive value for PTD <35 weeks (AUC=0.55, 95% CI: 0.43-0.67, p=0.355) or PTD <32 weeks (AUC=0.51, 95% CI: 0.30-0.74, p=0.851).

CONCLUSION

CL at 11-14 weeks does not appear to be predictive of PTD. Statistical analysis of CL did not show any predictive value for PTD <35 weeks, or <32 weeks and although it showed a predictive value for PTD at <37 weeks, the sensitivity was very low.

Ultrasonographic cervical length measurement at 10–14 and 20–24 weeks gestation and the risk of preterm delivery

OBJECTIVE

To compare cervical length measurements at 10-14 and 20-24 weeks gestation in asymptomatic women with singleton pregnancies and to assess the measurements as a predictor of preterm delivery.

STUDY DESIGN

In this prospective study, cervical length was measured in 152 asymptomatic women with singleton pregnancies using transvaginal ultrasonography at 10-14 and 20-24 weeks gestation. The primary outcome measure was spontaneous preterm delivery before 35 weeks of gestation. The mean cervical length was calculated at both stages, and lengths were compared between the term and preterm groups.

RESULTS

The rate of spontaneous preterm deliveries was 10.5%. The mean cervical length at 10-14 and 20-24 weeks was 40.5 and 37.1mm, respectively. The cervical length at 10-14 weeks was not significantly different between those who delivered at term (40.9 mm) and those who delivered preterm (38.6 mm). By contrast, the cervical length at 20-24 weeks was significantly shorter in the group that had preterm deliveries (28.4 mm) than in those who had term deliveries (37.8 mm) (P < 0.001). The cervical shortening was more apparent in the group that delivered prematurely (from 38.6 to 28.4 mm) than in that which delivered at term (from 40.9 to 37.8 mm).

CONCLUSION

Cervical length measurement used to predict preterm delivery was found to be more predictive at 20-24 weeks. Cervical length measurement at 10-14 weeks was not reliable for predicting preterm delivery. The mean cervical length tapered gradually from the first to the second scan, and the more rapid cervical shortening was found to be associated with increased risk for preterm delivery.

[Previous obstetric history and cervical length in pregnancy]

INTRODUCTION

The cervical length is a predictor of premature delivery or abortion. In order to detect the risks of such complications, it is necessary to establish the factors affecting the length of the cervix.

MATERIAL AND METHODS

A transversal prospective study was carried out in a sample of 579 pregnant women with low risk, singleton pregnancies of various gestational ages. Cervical length was measured by transvaginal ultrasound as part of routine pregnancy monitoring. At the same time, data on previous first-trimester or mid-trimester abortions, as well as on premature deliveries and term deliveries, were collected and taken into consideration.

RESULTS

The cervical length in primiparous women was not statistically significantly longer than in women with a previous pregnancy, except during the second trimester, (primiparous women: 33.8 mm, women with a previous pregnancy: 35.8 mm). Bearing in mind the empirical facts that the cervix in primiparous women, since intact, is significantly longer, the above mentioned findings cannot be easily explained. The cervix in women with a previous vaginal delivery was statistically significantly longer (35.6 mm) than in women with no vaginal delivery (34.09) (p = 0.011). In women with previous abortions of any kind, the cervical length was 34.2 mm. The cervical length in women without previous abortions was 34.7 mm, and there were no significant differences. Moreover, no statistically significant differences were established in women with or without previous abortions, regardless of the type.

CONCLUSION

Taking into consideration the data from previous obstetric histories, the results of our study indicate that cervices of women.

Controversies regarding cervical incompetence, short cervix, and the need for cerclage

Cervical incompetence (CI) is not an all or nothing phenomenon but a continuous variable. CI and preterm labor are not distinct entities but rather part of a spectrum leading to preterm delivery. Cervical length (CL) is an independent variable in the prediction of preterm delivery, to which it is inversely related. Application of a primary transvaginal cervical cerclage appears to be an unnecessary intervention in about 50% of women presenting with a history suggesting cervical incompetence. A better alternative for women with a history of or risk factors for CI is transvaginal ultrasonographic follow-up of CL. To facilitate the comparison of studies of CI, the authors suggest a nomenclature reflecting the different stages of prevention: primary, secondary, and tertiary transvaginal cervical cerclage.

Role of ultrasound in screening patients at risk for preterm delivery

The ultrasound assessment of the cervix has contributed to the understanding of the pathways to preterm birth. Transvaginal ultrasound measurement of the cervix provides an objective and noninvasive tool for the evaluation of cervical status. Despite widespread use of this procedure, standardization of measurement indications, technique, and interval between examinations has not been achieved. The American College of Radiology has recently recommended that the cervix and lower uterine segment be imaged as part of every obstetric ultra-sound examination in the second trimester. These guidelines specifically suggest a search for a short cervix (less than 30 mm) or funneling. The expert panel on women's imaging further recommended evaluating the cervix sonographically on both the initial examination and all follow-up examinations for twin gestations. The American Institute of Ultrasound in Medicine guidelines indicate that evaluation of the uterus, including cervix, should be performed, but does not indicate specifically that the cervix should be measured. In contrast, the American College of Obstetricians and Gynecologists, although recognizing that cervical length assessment may be helpful in predicting the risk of preterm delivery (particularly from a negative predictive value), does not recommend routine use of cervical length measurement because of the lack of proved treatment or intervention methods. A review of the literature suggests that at the time of this writing the role of routine screening of low-risk women with cervical length assessment by ultrasound is not supported. In contrast, in women at risk for preterm delivery(eg, women with a prior history of preterm birth or women with multiple gestations) cervical length assessment may be useful for its negative predictive value. At present, however, there is no therapeutic intervention that has been proved to decrease the risk of preterm delivery in women with a documented cervix on ultrasound.