Ultrasound examination at 37 weeks' gestation in the prediction of pregnancy outcome: the value of cervical assessment

The sonopartogram

The assessment of labor progress from digital vaginal examination has remained largely unchanged for at least a century, despite the current major advances in maternal and perinatal care. Although inconsistently reproducible, the findings from digital vaginal examination are customarily plotted manually on a partogram, which is composed of a graphical representation of labor, together with maternal and fetal observations. The partogram has been developed to aid recognition of failure to labor progress and guide management-specific obstetrical intervention. In the last decade, the use of ultrasound in the delivery room has increased with the advent of more powerful, portable ultrasound machines that have become more readily available for use. Although ultrasound in intrapartum practice is predominantly used for acute management, an ultrasound-based partogram, a sonopartogram, might represent an objective tool for the graphical representation of labor. Demonstrating greater accuracy for fetal head position and more objectivity in the assessment of fetal head station, it could be considered complementary to traditional clinical assessment. The development of the sonopartogram concept would require further undertaking of serial measurements. Advocates of ultrasound will concede that its use has yet to demonstrate a difference in obstetrical and neonatal morbidity in the context of the management of labor and delivery. Taking a step beyond the descriptive graphical representation of labor progress is the question of whether a specific combination of clinical and demographic parameters might be used to inform knowledge of labor outcomes. Intrapartum cesarean deliveries and deliveries assisted by forceps and vacuum are all associated with a heightened risk of maternal and perinatal adverse outcomes. Although these outcomes cannot be precisely predicted, many known risk factors exist. Malposition and high station of the fetal head, short maternal stature, and other factors, such as caput succedaneum, are all implicated in operative delivery; however, the contribution of individual parameters based on clinical and ultrasound assessments has not been quantified. Individualized risk prediction models, including maternal characteristics and ultrasound findings, are increasingly used in women's health-for example, in preeclampsia or trisomy screening. Similarly, intrapartum cesarean delivery models have been developed with good prognostic ability in specifically selected populations. For intrapartum ultrasound to be of prognostic value, robust, externally validated prediction models for labor outcome would inform delivery management and allow shared decision-making with parents.

Prediction of labor outcome pilot study: evaluation of primiparous women at term

BACKGROUND

Emergency operative delivery is associated with high fetal and maternal morbidity and mortality. It is of high importance to find means to predict the delivery mode before the onset of labor.

OBJECTIVE

This study aimed to investigate the potential of combined sonographic and clinical determination to predict the mode of delivery at term.

STUDY DESIGN

An observational prospective cohort study was deployed in a tertiary maternity hospital (Emergency County Hospital Craiova). Unselected low-risk primiparous pregnant women were evaluated weekly at term for ultrasound determinations (estimated fetal weight, head descent parameters, occiput posterior, cervical length), Bishop score, and maternal characteristics (age, height, weight). A thorough statistical analysis determined which variables were significantly correlated with the delivery mode.

RESULTS

Data from 276 term primiparous women were analyzed. Head descent parameters were strongly and significantly correlated with each other, but only progression distance was correlated with the delivery mode (gestational weeks 37, 38, 41, and the week before delivery). In the week before delivery, measurements of head-to-perineum distance and angle of progression reached almost significant P levels of.055 and.07, respectively. The following variables were significantly correlated with the delivery mode: body mass index in all term evaluations; progression distance for weeks 37 and 38; maternal age for week 39; Bishop score, estimated fetal weight, and occiput posterior for week 40; and body mass index, estimated fetal weight, and progression distance for the week before delivery. We also provided logistic regression equations for each week with correct delivery mode prediction, except for week 38. Cutoff values were established for each significant parameter per week. The cutoff values must be read in conjunction with the area under the curve, which ranged from 0.55 to 0.73, depending on the variable.

CONCLUSION

There are strong and significant correlations among the "head descent" ultrasound measurements at term. Body mass index is predictive of labor outcomes throughout term evaluations. Progression distance and body mass index measured at 37 to 38 weeks' gestation correlate with the delivery mode and apparently can be used to forecast the delivery mode when the pregnancy reaches term. For the week before delivery, measurements of estimated fetal weight and progression distance can be used to forecast the delivery mode, perhaps as part of a policy for pregnant women with prelabor clinical signs. Larger studies with more data, particularly better-balanced data, are needed.

Prediction of spontaneous onset of labor at term (PREDICT study): Research protocol

Background

Recent studies have shown that elective induction of labor versus expectant management after 39 weeks of pregnancy result in lower incidence of perinatal complications, while the proportion of cesarean deliveries remains stable, or even decreases. Still, evidence regarding collateral consequences of the potential increase of induction of labor procedures is still lacking. Also, the results of these studies must be carefully interpreted and thoroughly counter-balanced with women’s thoughts and opinions regarding the active management of the last weeks of pregnancy. Therefore, it may be useful to develop a tool that aids in the decision-making process by differentiating women who will spontaneously go into labor from those who will require induction.

Objective

To develop a predictive model to calculate the probability of spontaneous onset of labor at term.

Methods

We designed a prospective national multicentric observational study including women enrolled at 39 weeks of gestation, carrying singleton pregnancies. After signing an informed consent form, several clinical, ultrasonographic, biophysical and biochemical variables will be collected by trained staff. If delivery has not occurred at 40 weeks of pregnancy, a second visit and evaluation will be performed. Prenatal care will be continued according to current hospital guidelines. Once recruitment is completed, the information gathered will be used to develop a logistic regression-based predictive model of spontaneous onset of labor between 39 and 41 weeks of gestation. A secondary exploration of the data collected at 40 weeks, as well as a survival analysis regarding time-to-delivery outcomes will also be performed. A total sample of 429 participants is needed for the expected number of events.

Conclusion

This study aims to develop a model which may help in the decision-making process during follow-up of the last weeks of pregnancy.

Trial registration

NCT05109247 (clinicaltrials.gov).

Machine learning to predict pregnancy outcomes: a systematic review, synthesizing framework and future research agenda

Machine Learning (ML) has been widely used in predicting the mode of childbirth and assessing the potential maternal risks during pregnancy. The primary aim of this review study is to explore current research and development perspectives that utilizes the ML techniques to predict the optimal mode of childbirth and to detect various complications during childbirth. A total of 26 articles (published between 2000 and 2020) from an initial set of 241 articles were selected and reviewed following a Systematic Literature Review (SLR) approach. As outcomes, this review study highlighted the objectives or focuses of the recent studies conducted on pregnancy outcomes using ML; explored the adopted ML algorithms along with their performances; and provided a synthesized view of features used, types of features, data sources and its characteristics. Besides, the review investigated and depicted how the objectives of the prior studies have changed with time being; and the association among the objectives of the studies, uses of algorithms, and the features. The study also delineated future research opportunities to facilitate the existing initiatives for reducing maternal complacent and mortality rates, such as: utilizing unsupervised and deep learning algorithms for prediction, revealing the unknown reasons of maternal complications, developing usable and useful ML-based clinical decision support systems to be used by the expecting mothers and health professionals, enhancing dataset and its accessibility, and exploring the potentiality of surgical robotic tools. Finally, the findings of this review study contributed to the development of a conceptual framework for advancing the ML-based maternal healthcare system. All together, this review will provide a state-of-the-art paradigm of ML-based maternal healthcare that will aid in clinical decision-making, anticipating pregnancy problems and delivery mode, and medical diagnosis and treatment.

Can ultrasound predict the delivery time of patients with previous cesarean section in the 37th gestational week? A prospective cross-sectional study

BACKGROUND

The aim was to investigate factors that predict when patients with previous cesarean section will undergo cesarean section (CS) using ultrasonography in the 37th gestational week.

MATERIAL AND METHODS

In this prospective cross-sectional study, a total of 166 patients with previous CS who presented to the hospital for routine checks at the 37^0/7th gestational week were included in the study. Uterine-related, fetus-related, and patient-related factors that affect labor time were analyzed by the same physician at admission, and the patients were then divided into two groups as those having CS at early term (37^0/7 to 38^{6/7 weeks} of gestation) and full-term (39^0/7 to 40^{6/7 weeks} of gestation). Ninety-four patients underwent CS at full-term and 72 patients underwent CS at the early term in the study.

RESULTS

There was no significant difference for age (years), parity, weight gain, previous cesarean number, cervical length, myometrial thickness, estimated fetal weight, and full lower uterine segment thickness between the groups (p>.05). In the full-term group, 58% had a history of vaginal birth, whereas, in the early-term group, 42% had a history of vaginal birth (p < .05). Vaginal birth history was found to be independently associated with reaching full-term (respectively, OR: 2.876, 95% CI: [1.227-6.738]; p = .015) in all patients. Two different regression models were created to predict different CS times after the 37th week of pregnancy. Weight gain was found to be independently associated with CS time within the first seven days after admission (OR: 1.267, 95% CI: [1.003-1.599]; p = .047). Vaginal birth history and estimated fetal weight were found to be independently associated with CS time in the 8th day and further after admission (OR: 0.244, 95% CI: [0.089-0.675]; p = .007 and OR: 1.002, 95% CI: [1.000-1.003]; p = .047).

CONCLUSION

Vaginal birth history can be useful to predict reaching full-term in patients with previous CS. Determination of such risk factors is important in terms of reducing the frequency of emergency cesarean delivery.

Mid-pregnancy cervical length as a risk factor for cesarean section in women with twin pregnancies

Objective:

It is well known that a short cervix at mid-pregnancy is a risk factor for spontaneous preterm birth in both singleton and twin gestations. Recent evidence also suggests that a long cervix at mid-pregnancy is a predictor of the risk of cesarean section (C/S) in singleton gestation. The purpose of this study was to determine whether a long cervix at mid-pregnancy was associated with an increased risk of C/S in women with twin pregnancies.

Methods:

We enrolled 746 women pregnant with twins whose cervical length was measured by trans-vaginal ultrasonography at a mean of 22 weeks of gestation and who delivered in our institution. Cases with a short cervix [cervical length (CL) <15 mm] were excluded. Cases were divided into four groups according to the quartile of CL.

Results:

The rate of C/S increased according to the quartile of CL (47% in the 1st quartile, 51% in the 2nd quartile, 56% in the 3rd quartile and 62% in the 4th quartile, P<0.005, χ2 for trend). CL was an independent risk factor for C/S even after adjustment for confounding variables. When confining analysis to women who delivered after a trial of labor (n=418), to nulliparous women (n=633) or to those who delivered at late preterm or full term (n=666), the rate of C/S also increased according to the quartile of CL, and the relationship between CL and the risk of C/S remained significant after adjustment in each group.

Conclusion:

In women pregnant with twins, long CL at mid-pregnancy was a risk factor for C/S.

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.

Ultrasound cervical length measurement in prediction of labor induction outcome

Induction of labor is one of the most common procedures in modern obstetrics, with an incidence of approximately 20% of all deliveries. Not all of these inductions result in vaginal delivery; some lead to cesarean sections, either for emergency reasons or for failed induction. That's why, It seems necessary to outline strategies for the improvement of the success rate of induced deliveries. Traditionally, the identification of women in whom labor induction is more likely to be successful is based on the Bishop score. However, several studies have shown it to be subjective, with high variation and a poor predictor of the outcome of labor induction. Transvaginal sonography for cervical measurement can be a more objective criterion in assessing the success of labor induction. Many studies have been done recently to compare cervical measurement and Bishop Score in labor induction.This paper reviewed the literature that evaluated sonographic cervical length measurement to predict induction of labor outcome.

Use of translabial three-dimensional power Doppler ultrasound for cervical assessment before labor induction

OBJECTIVE

To compare translabial three-dimensional (3D) power Doppler ultrasound with Bishop score and transvaginal ultrasound measurements for cervical assessment before induction of labor with dinoprostone or cervical ripening balloon.

MATERIALS AND METHODS

Translabial cervical volume and length, vascularization indices and transvaginal cervical length were measured. Results were compared among women who had vaginal delivery at 24 h or less and more than 24 h after the insertion of the dinoprostone vaginal insert or cervical ripening balloon and among women who had vaginal delivery and cesarean delivery for failure to go into labor or failure to progress.

RESULTS

There was no correlation between the time to delivery after a ripening agent was applied and translabial cervical volume, translabial cervical length, vascularization index (VI), flow index (FI), vascularization flow index (VFI), transvaginal cervical length and Bishop scores. The ultrasonographic measurements were no different among women who had vaginal delivery at 24 h or less and more than 24 h and among women who had vaginal delivery and cesarean delivery for failure to go into labor or failure to progress.

CONCLUSION

In this study, we failed to demonstrate the superiority of translabial 3D ultrasonography over Bishop score and transvaginal ultrasonography for predicting the success of induction of labor.

Ultrasonographic assessment of cervical length in pregnancies scheduled for a cesarean delivery: prediction of early spontaneous onset of labor

AIM

To investigate whether the cervical length measured by transvaginal ultrasound at 35 to 36 weeks of gestation is predictive of spontaneous early onset of labor in pregnancies scheduled for elective cesarean section (CS).

STUDY DESIGN

This was a prospective observational study on 167 women scheduled for elective CS at 39 weeks of gestation. The cervical length was measured ultrasonographycally at 35 to 36 weeks of gestation and the pregnancies characteristics were recorded. The presence or absence of spontaneous onset of labor before the time scheduled for elective CS was related to cervical length and pregnancies characteristics.

RESULTS

Of the 167 pregnancies enrolled, 25 (14.97%) underwent early spontaneous onset of labor before the time scheduled for the elective CS. The cervical length was significantly shorter in these women when compared with those delivering with an elective CS (21 vs. 30 mm z=5.49 P<0.0001). The presence of ≥2 previous CS as an indicator for elective CS resulted a significant predictor of early onset of labor in univariate analysis (P=0.01). Multivariate logistic regression analysis showed that cervical length (adjusted odds ratio 1.40; 95% confidence interval (CI) 1.22-1.61; P≤0.0001) was the only predictor for the early onset of labor. The area under the receiver-operating characteristics curve for the prediction of early onset of labor was 0.844 (95% CI 0.738-0.950) for cervical length as test variable. Kaplan-Meier analysis demonstrated that a cervical length <24 mm was significantly associated with a short time interval to delivery (log rank test χ2=99,98; P≤0.0001).

CONCLUSION

Cervical length at 35-36 weeks of gestation provides information about the likelihood of spontaneous early onset of labor in pregnancies scheduled for CS and may be useful in individualizing the gestational age for elective CS.

Ultrasound examination at term for predicting the outcome of delivery in women with a previous cesarean section

OBJECTIVE

To evaluate if ultrasound variables at term are associated with the mode of delivery in women with previous cesarean section (PCS).

METHODS

This was a prospective study of singleton pregnant women who planned a trial of vaginal birth after cesarean delivery. Cervical length, posterior cervical angle, head-perineum distance, and estimated fetal weight were measured at 37-39 weeks of gestation.

RESULTS

One hundred forty-four pregnancies were examined and vaginal delivery was achieved in 98 women (73%). Logistic regression analysis identified cervical length, head-perineum distance, age, previous vaginal delivery, previous cesarean for dystocia, and Bishop score as predictors of vaginal delivery. Combining ultrasound and clinical parameters, two models for risk scoring that differ in the variable Bishop score or cervical length were constructed. The AUC of these models was 0.867 and 0.855, respectively.

CONCLUSIONS

In women with a PCS, measurement of cervical length and head-perineum distance at term is associated with the mode of delivery. A combination of clinical and sonographic parameters at term can predict the likelihood of vaginal delivery.

Transvaginal ultrasound cervical length for prediction of spontaneous labour at term: a systematic review and meta-analysis

BACKGROUND

The possibility to predict the delivery date is a question frequently raised by pregnant women. However, a clinician has currently little to predict when a woman at term will deliver.

OBJECTIVE

To evaluate the predictive accuracy of transvaginal ultrasound (TVU) cervical length (CL) for spontaneous onset of labour in singleton gestation enrolled at term by a meta-analysis.

SEARCH STRATEGY

We performed a literature search in electronic databases.

SELECTION CRITERIA

We included only studies assessing the accuracy of TVU CL in prediction of spontaneous onset of labour in singleton gestations with vertex presentation who were enrolled at term.

DATA COLLECTION AND ANALYSIS

The primary outcome was the accuracy of CL for prediction of spontaneous labour within 7 days. Pooled sensitivities and specificities were calculated.

MAIN RESULTS

Five studies including 735 singleton gestations were included. For the prediction of spontaneous labour within 7 days for CL <30 mm the pooled sensitivity was 64% and pooled specificity was 60%. The higher the CL, the better the sensitivity; the lower the CL, the better the specificity. A woman with a singleton gestation at term and a TVU CL of 30 mm has a <50% chance of delivering within 7 days, while one with a TVU CL of 10 mm has an over 85% chance of delivery within 7 days.

CONCLUSIONS

TVU CL at term has moderate value in predicting the onset of spontaneous labour. A woman with a TVU CL of 10 mm or less has a high chance of delivering within a week.

TWEETABLE ABSTRACT

Cervical length at term has moderate value in predicting the onset of spontaneous labour.

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.

Association between shortened cervical length at 34-36 weeks' gestation and term labour in Asian women

Cervical length was measured at 34-36 weeks' gestation by transvaginal ultrasound. The purpose of measurement of cervical length before term was to reveal the association with the onset of term labour. This was a retrospective study of 362 women who were delivered at term at Mizmedi hospital, between August 2006 and November 2011. There was significant linear correlation between cervical length and the scan-to-labour interval in women with labour before 41 weeks. The measurement of cervical length at 34-36 weeks' gestation might be helpful in predicting the onset of term labour before 41 weeks.

Predicting mode of delivery using mid-pregnancy ultrasonographic measurement of cervical length

BACKGROUND

It has been recognized that preterm labor is related to short cervical length and that poor progress in labor is a major indication for cesarean section at term. We therefore hypothesize that long cervix is not associated with increased risk of cesarean delivery during labor at term.

OBJECTIVES

The objective is to determine the relationship between cervical length at mid-pregnancy and mode of delivery and preterm delivery.

MATERIALS AND METHODS

Trans-vaginal ultrasonographic scan measurement of cervical length was done for 281 pregnant women at a mean gestational age of 22 weeks. These women were followed up till delivery and the mode of delivery and the cervical length were analyzed for associations.

RESULTS

Cesarean section due to poor progress in labor at term constituted 11.7%. The cesarean section for the highest quartile cervical length (40-67 mm) was 50% (P value 0.0018 for trend). Of the 33 women whose mode of delivery was cesarean section due to poor progress 18 (54.5%) had cervical length of more than 40 cm. The likelihood ratio of cesarean section due to poor progress of labor at term among women at the upper quartile cervical length is 10.28 (P value 0.0013)

CONCLUSION

Long cervical length at mid-pregnancy predicts the possibility of cesarean delivery early in pregnancy. Hence, cervical length in mid-pregnancy can be of value in predicting the mode of delivery in early pregnancy.

Cervical length at 30-32 weeks and the risk of Cesarean delivery in twin pregnancies

OBJECTIVES

To estimate the association between the cervical length (CL) measurement at 30-32 weeks and the mode of delivery in twin pregnancies.

METHODS

This was a retrospective study of a cohort, from 2005-2010, of 265 twin pregnancies with a CL measurement at 30-32 weeks. We compared the CL measurement at 30-32 weeks based on mode of delivery. We then analyzed our data across four subgroups, based on the CL measurement quartiles at 30-32 weeks. We performed this analysis in all patients, and also performed a planned subgroup analysis of 130 patients who attempted a vaginal delivery.

RESULTS

In all patients, including those who attempted a vaginal delivery, the mean CL at 30-32 weeks was significantly shorter in women who delivered vaginally compared with women who had a Cesarean section. The likelihood of Cesarean delivery increased significantly with increasing CL measurement across the groups defined by measurement quartiles. On adjusted analysis controlling for maternal age, race, in-vitro fertilization, chorionicity, induction of labor and prior vaginal delivery, the CL measurement at 30-32 weeks was independently associated with mode of delivery.

CONCLUSIONS

In twin pregnancies, the CL at 30-32 weeks is significantly associated with the likelihood of Cesarean delivery. A longer CL may represent underdevelopment of the uterus, leading to a higher risk of Cesarean delivery in labor at term.

Effect of membrane sweeping on cervical length by transvaginal ultrasonography and impact of cervical shortening on cesarean delivery

OBJECTIVES

The purpose of this study was to evaluate cervical length changes after membrane sweeping and the effect of cervical shortening on pregnancy outcomes.

METHODS

Low-risk women at 40 weeks' gestation undergoing membrane sweeping to expedite labor were recruited. Participants were scheduled for labor induction at 41 weeks' gestation. Transvaginal ultrasonography was performed immediately before and after membrane sweeping to measure the cervical length. Three presweep and postsweep cervical lengths were measured. The shortest lengths before and after the sweep were taken as the representative lengths. The effect of membrane sweeping on cervical length was analyzed. Multivariable logistic regression analysis was performed to evaluate the effect of cervical shortening on labor induction and the mode of delivery.

RESULTS

For the 160 participants, the mean presweep cervical length ± SD was 21.0 ± 10.0 mm; the postsweep length was 23.8 ± 10.9 mm, an average increase of 2.8 ± 0.6 mm (P < .001). Cervical shortening after membrane sweeping was noted in 53 of 160 cases (33%). Cervical shortening was associated with a reduction in all-cause cesarean delivery but not labor induction on bivariate analysis. After adjustment for maternal age, parity, presweep Bishop score, postsweep cervical length, oxytocin augmentation, epidural analgesia, and meconium-stained fluid, cervical shortening after membrane sweeping was independently predictive of a reduction in cesarean deliveries (adjusted odds ratio, 0.24; 95% confidence interval, 0.06-0.90; P = .034).

CONCLUSIONS

Membrane sweeping was associated with lengthening of the cervix. A shortened cervix after sweeping was independently predictive of vaginal delivery.

Biochemical and biophysical predictors of the response to the induction of labor in nulliparous postterm pregnancy

OBJECTIVE

The objective of the study was to evaluate the clinical, sonographic, and hormonal variables that influence the success of labor induction in nulliparous postterm pregnancies.

STUDY DESIGN

Fifty nulliparous women with a single postterm pregnancy receiving a slow-release prostaglandin estradiol pessary were prospectively enrolled, and clinical characteristics were analyzed in relation to success of induction of labor. Clinical, sonographic, and hormonal variables were analyzed by univariate statistical analysis and multivariate logistic regression for the prediction of successful induction.

RESULTS

The group of patients delivering within 24 hours differed significantly from the remaining patients by higher Bishop scores, body mass indices, estradiol serum concentrations, estriol to estradiol ratios, and shorter cervices. The combination of cervical length and estriol to estradiol ratio achieved a sensitivity of 100% (95% confidence interval, 71.3-100%) and a specificity of 94.1% (95% confidence interval, 80.3-99.1%).

CONCLUSION

Cervical length and the estriol to estradiol ratio represent good predictive indicators of the response to the induction of labor in postterm pregnancies.

The molecular basis for sonographic cervical shortening at term: identification of differentially expressed genes and the epithelial-mesenchymal transition as a function of cervical length

OBJECTIVE

The purpose of this study was to determine whether cervical shortening of a ripe cervix at term is associated with changes in the cervical transcriptome.

STUDY DESIGN

Sonographically measured cervical lengths and biopsy specimens were obtained from 19 women at term who were not in labor with a ripe cervix. Affymetrix HG-U133 Plus 2.0 arrays (Affymetrix Inc, Santa Clara, CA) were used. Gene expression was analyzed as a function of cervical length. Gene Ontology, pathway analyses, quantitative real-time reverse transcription-polymerase chain reaction, and immunohistochemistry were performed.

RESULTS

Cervical length shortening was associated with differential expression of 687 genes. Fifty-four biologic processes, 22 molecular functions, and 9 pathways were enriched. Quantitative real-time reverse transcription-polymerase chain reaction analysis confirmed differential expression of 13 genes. Bone morphogenetic protein-7, claudin-1, integrin beta-6, and endometrial progesterone-induced protein messenger RNA, and protein expressions were down-regulated with cervical shortening.

CONCLUSION

Sonographic cervical shortening in patients at term who are not in labor with a ripe cervix is associated with changes in the uterine cervix transcriptome. The epithelial-mesenchymal transition may participate in the mechanism of cervical shortening at term.

Clinical and sonographic parameters at 37 weeks' gestation for predicting the risk of primary Cesarean delivery in nulliparous women

OBJECTIVES

To identify the clinical and sonographic parameters at 37 weeks' gestation that predict the risk of Cesarean delivery in labor for nulliparas.

METHODS

This prospective observational study recruited nulliparas with singleton pregnancies at 37 weeks' gestation. Determination of the Bishop score, ultrasound measurement of the cervical length, and fetal biometry were performed. The clinical parameters studied were maternal age, height and weight and Bishop score. The sonographic parameters included fetal biparietal diameter, femur length, abdominal circumference (AC), estimated fetal weight (EFW), amniotic fluid index and cervical length.

RESULTS

Four hundred and fifty-three women were examined; 57 women (12.6%) underwent an emergency Cesarean delivery in labor. Logistic regression analysis identified maternal age and height and fetal AC and EFW, but not cervical length or Bishop score, as the best predictors of Cesarean delivery. Of these predictors, maternal age and height and fetal AC at 37 weeks were included in a final model for risk scoring. The model was shown to have an adequate goodness of fit (P = 0.473), and the area under the receiver-operating characteristics curve was 0.758, indicating reasonably good discrimination.

CONCLUSIONS

Maternal age and height and fetal AC and EFW at 37 weeks' gestation are the most important parameters in predicting the risk of Cesarean delivery in nulliparas; sonographic measurement of the cervical length and the Bishop score were not predictive of Cesarean delivery. A predictive model using these parameters at 37 weeks provides useful information in the decision-making process regarding the mode of delivery.

Sonographic longitudinal cervical length measurements in nulliparous women at term: prediction of spontaneous onset of labor

OBJECTIVE

The aim of this study was to predict spontaneous onset of labor by serial transvaginal ultrasound measurement of cervical length (CL) in a homogeneous population of nulliparous women at term.

METHODS

162 nulliparous women with singleton fetuses in cephalic presentation were examined at weekly intervals from 36 weeks' gestation to delivery. CL was measured by transvaginal ultrasound in the supine and upright positions.

RESULTS

There was a significant decrease in CL in the last 12 days prior to delivery. However, this decrease was small with substantial variation between individuals. Women with spontaneous onset of labor could be divided into three different groups: those with unchanged CL before delivery; those with a fall in CL in the last 2 weeks prior to delivery; and those with a gradual change in CL starting before the last 2 weeks prior to delivery. A single CL measurement below 30 mm between 37 and 38 weeks of gestation predicted spontaneous onset of labor before 41 weeks' gestation with a sensitivity of 46%, specificity of 78%, positive predictive value (PPV) of 82%, negative predictive value (NPV) of 40% in the supine position; and sensitivity of 53%, specificity of 72%, PPV of 81%, NPV of 40% in the upright position.

CONCLUSION

Between 37 and 38 weeks' gestation, spontaneous onset of labor before 41 weeks can be predicted by a CL measurement, but with low sensitivity and NPV. Inter-individual variations in CL and in CL changes are large, which hampers the value of single and repeated CL measurements for the prediction of spontaneous onset of labor at term.

Cervical length and maternal factors in expectantly managed prolonged pregnancy: prediction of onset of labor and mode of delivery

OBJECTIVE

To examine the value of combining cervical length and maternal characteristics in a prolonged-pregnancy clinic in the prediction of the probability of firstly, spontaneous onset of labor within the subsequent 10 days and secondly, the need for Cesarean section.

METHODS

This was a prospective study of women with singleton pregnancies attending an ultrasound-based prolonged-pregnancy clinic at 40 + 4 to 41 + 6 weeks of gestation. The policy was to delay induction of labor by 7-10 days unless there was evidence of a specific medical or obstetric indication or the mother wanted earlier delivery. The measurement of cervical length was not given to the obstetrician, midwife or patient. Regression analysis was used to determine which of the following factors had a significant contribution in predicting induction of labor: maternal age, body mass index (BMI), ethnic origin, parity and cervical length. Regression analysis was also used to determine which of the factors amongst the maternal characteristics, onset of labor and cervical length provided significant prediction of Cesarean section.

RESULTS

We examined 2316 pregnancies but we excluded from further analysis 452 (19.5%) cases because iatrogenic delivery was carried out within the subsequent 6 days, including 427 cases of induction of labor (340 at the request of the mother and 87 for medical indications) and 25 cases of Cesarean section. In the remaining 1864 cases there was spontaneous onset of labor and delivery within 10 days in 1536 (82.4%) and induction of labor in 7-10 days in 328 (17.6%). The rate of Cesarean section was 15.2% (233 of 1536) in those with spontaneous onset of labor and 36.0% (118 of 328) in those whose labor was induced. Regression analysis demonstrated that in the prediction of induction of labor there were significant contributions from cervical length, BMI, parity and gestational age, and in the prediction of Cesarean section there were significant contributions from onset of labor, cervical length, BMI, parity and ethnicity.

CONCLUSION

Ultrasonographic measurement of cervical length at 41 weeks together with maternal factors can define the patient-specific probability of spontaneous onset of labor in the subsequent week and the risk of Cesarean section.

Cervical length at mid-pregnancy and the risk of primary cesarean delivery

BACKGROUND

Physiological and biochemical studies suggest that normal parturition at term is dependent on programmed development of the uterus in early pregnancy. It is recognized that a short cervix in mid-pregnancy is associated with an increased risk of spontaneous preterm birth. We hypothesized that a long cervix in mid-pregnancy would be associated with an increased risk of cesarean delivery during labor at term.

METHODS

We studied 27,472 primiparous women who had a cervical length of 16 mm or more at a median of 23 weeks of gestation and who ultimately delivered a live infant in labor at term.

RESULTS

The rate of cesarean delivery at term was lowest (16.0%) among women with a mid-pregnancy cervical length in the lowest quartile (16 to 30 mm) and was significantly greater in the second quartile (18.4%, 31 to 35 mm), third quartile (21.7%, 36 to 39 mm), and fourth quartile (25.7%, 40 to 67 mm) (P<0.001 for trend). The odds ratio for cesarean delivery among women in the fourth quartile, as compared with the first quartile, was 1.81 (95% confidence interval [CI], 1.66 to 1.97), and the odds ratio adjusted for maternal age, body-mass index, smoking status, race or ethnic group, gestational age at birth, spontaneous or induced labor, birth-weight percentile, and hospital of delivery was 1.68 (95% CI, 1.53 to 1.84; P<0.001). The increased risk of cesarean delivery was attributable to procedures performed for poor progress in labor.

CONCLUSIONS

The cervical length at mid-pregnancy is an independent predictor of the risk of cesarean delivery at term in primiparous women.

Ultrasound assessment of cervical length in prolonged pregnancy: prediction of spontaneous onset of labor and successful vaginal delivery

OBJECTIVES

To evaluate the usefulness of sonographic assessment of cervical length in the prediction of spontaneous onset of labor and of vaginal delivery.

METHODS

Two hundred and six women who attended a dedicated postdates clinic at 41 + 3 weeks of pregnancy and agreed to the assessment of cervical length using transvaginal ultrasound imaging were included in the study. Those who had not delivered at 42 weeks were offered induction of labor. The labor details were recorded prospectively, and the onset of spontaneous labor and mode of delivery were correlated with cervical length data.

RESULTS

Women who underwent spontaneous onset of labor (n = 112) had a significantly shorter cervical length (mean (SD) 25.0 (8.3) mm) than had women whose labor was induced (n = 67; mean (SD) 29.7 (8.5) mm). Logistic regression analysis showed that cervical length was an independent predictor of the likelihood of spontaneous labor in nulliparous women, and of vaginal delivery in both nulliparous and parous women. Parity had no independent effect on the onset of spontaneous labor, but was an independent predictor of the likelihood of vaginal delivery.

CONCLUSIONS

Sonographic assessment of cervical length is a significant independent predictor of the likelihood of the onset of spontaneous labor in nulliparous women, and of successful vaginal delivery in both nulliparous and parous women with prolonged pregnancy.

Cervical length and the risk of spontaneous labor at term

OBJECTIVE

To investigate the relationship between cervical length (CL) at 37 to 40 weeks and delivery within 7 days and delivery by 41 weeks.

STUDY DESIGN

We performed transvaginal ultrasound to measure CL in women with singleton gestations at 37 to 40 weeks. We then used a receiver operating characteristic curve (ROC) to assess the relationship between CL and delivery within 7 days and delivery by 41 weeks.

RESULT

For the 120 women included in the analysis, the mean CL (+/-s.d.) was 25.3+/-9.8 mm. The logistic regression model to predict each of the outcomes includes gestational age at ultrasound (GA-US) and CL. Neither birthweight, nor parity seems to affect the probability of delivery within 7 days. The ROC curve was used to assess the probability of spontaneous labor within 7 days at each CL measurement. The likelihood ratio of delivery within 7 days when CL is < or = 10 mm is 12.

CONCLUSION

CL measurement at 37-40 weeks is an independent predictor of delivery within 7 days and delivery by 41 weeks regardless of GA-US. This information can be utilized when counseling patients regarding the management of term pregnancies.

Prediction of prolonged pregnancy in nulliparous women by transvaginal ultrasonographic measurement of cervical length at 20-24 weeks and 37 weeks

This study was done to evaluate transvaginal ultrasonographic measurement of cervical length at 20 to 24 weeks and 37 weeks as a predictor of prolonged pregnancy (defined as a pregnancy that extended beyond 41+2 weeks of gestation [289 days]) in nulliparous women. This prospective observational study enrolled 149 consecutive nulliparous women with singleton gestation at 37 weeks. Cervical length was measured by transvaginal ultrasonography at 20 to 24 weeks and 37 weeks. Cervical length at 37 weeks, but not at 20 to 24 weeks, was significantly longer in women delivered at >41+2 weeks than in those delivered at <or=41+2 weeks (p<0.005). There was a significant correlation between cervical length at 37 weeks and gestational age at delivery (Pearson correlation coefficient, r=0.387, p<0.0001). In the receiver operating curve, the best cut-off value of cervical length at 37 weeks for the prediction of prolonged pregnancy was 30 mm, with a sensitivity of 78% and a specificity of 62%. Cervical length assessed by transvaginal ultrasonography at 37 weeks can predict the likelihood of prolonged pregnancy in nulliparous women. However, there is no association between cervical length at 20 to 24 weeks and the occurrence of prolonged pregnancy.

Bishop score and ultrasound assessment of the cervix for prediction of time to onset of labor and time to delivery in prolonged pregnancy

OBJECTIVES

To determine the ability of Bishop score and sonographic cervical length to predict time to spontaneous onset of labor and time to delivery in prolonged pregnancy.

METHODS

Ninety-seven women underwent transvaginal ultrasound examination and palpation of the cervix at 291-296 days' gestation according to ultrasound fetometry at 12-20 weeks' gestation. Sonographic cervical length and Bishop score were recorded. Multivariate logistic regression analysis was used to determine which variables were independent predictors of the onset of labor/delivery < or = 24 h, < or = 48 h, and < or = 96 h. Receiver-operating characteristics (ROC) curves were drawn to assess diagnostic performance.

RESULTS

In nulliparous women (n = 45), both Bishop score and sonographic cervical length predicted the onset of labor/delivery < or = 24 h and < or = 48 h (area under ROC curve for the onset of labor < or = 24 h 0.79 vs. 0.80, P = 0.94; for delivery < or = 24 h 0.81 vs. 0.85, P = 0.64; for the onset of labor < or = 48 h 0.73 vs. 0.74, P = 0.90; for delivery < or = 48 h 0.77 vs. 0.71, P = 0.50). Only Bishop score discriminated between nulliparous women who went into labor/delivered < or = 96 h or > 96 h. A logistic regression model including Bishop score and cervical length was superior to Bishop score alone in predicting delivery < or = 24 h (area under ROC curve 0.93 vs. 0.81, P = 0.03) and superior to Bishop score alone and cervical length alone in predicting the onset of labor < or = 24 h (area under ROC curve 0.90 vs. 0.79, P = 0.06; and 0.90 vs. 0.80, P = 0.06). In parous women (n = 52), Bishop score and sonographic cervical length predicted the onset of labor/delivery < or = 24 h (area under ROC curve for the onset of labor 0.75 vs. 0.69, P = 0.49; for delivery 0.74 vs. 0.70, P = 0.62), but only Bishop score discriminated between women who went into labor/delivered < or = 48 h and > 48 h. Three parous women had not gone into labor and six had not given birth at 96 h. In parous women logistic regression models including both Bishop score and cervical length did not substantially improve prediction of the time to onset of labor/delivery.

CONCLUSIONS

In prolonged pregnancy Bishop score and sonographic cervical length have a similar ability to predict the time to the onset of labor and delivery. In nulliparous women the use of logistic regression models including Bishop score and cervical length is likely to offer better prediction of the onset of labor/delivery < or = 24 h than the use of the Bishop score alone.

Three-dimensional ultrasound assessment of the cervix for predicting time to spontaneous onset of labor and time to delivery in prolonged pregnancy

OBJECTIVES

To determine whether three-dimensional (3D) ultrasound including power Doppler examination of the cervix is useful for predicting time to spontaneous onset of labor or time to delivery in prolonged pregnancy.

METHODS

A prospective study was conducted in 60 women who went into spontaneous labor. All underwent transvaginal 3D power Doppler ultrasound examination of the cervix immediately before a prolonged-pregnancy check-up at > or = 41 + 5 gestational weeks. Univariate and multivariate logistic regression analysis was used to determine which of the following variables predicted spontaneous onset of labor > 24 h and > 48 h and vaginal delivery > 48 h and > 60 h: length, anteroposterior (AP) diameter and width of the cervix and of any cervical funneling; cervical volume (cm3); vascularization index (VI); flow index (FI); vascularization flow index (VFI); parity; and Bishop score. Multivariate logistic regression analysis was carried out both with and without Bishop score as a predictive variable. Receiver-operating characteristics (ROC) curves were used to describe the diagnostic performance of the tests.

RESULTS

The areas under the ROC curves for Bishop score, cervical length, and logistic regression models did not differ significantly (areas ranging from 0.72 to 0.82). If Bishop score was not included in the logistic regression model, cervical length, VI and FI independently predicted delivery > 48 h, the likelihood increasing with increasing cervical length, decreasing VI and increasing FI.

CONCLUSIONS

In prolonged pregnancy cervical vascularization as estimated by 3D power Doppler ultrasound is related to time to delivery > 48 h, but the likelihood of delivery > 48 h can be predicted equally well using Bishop score alone or sonographic cervical length alone.

Reference data representative of normal findings at two-dimensional and three-dimensional gray-scale ultrasound examination of the cervix from 17 to 41 weeks' gestation

OBJECTIVES

To create reference values representative of normal findings on two-dimensional (2D) and three-dimensional (3D) transvaginal ultrasound (TVS) examination of the cervix from 17 to 41 weeks' gestation and to determine the agreement between cervical measurements taken by 2D and 3D TVS.

METHODS

Cross-sectional study covering 17 to 41 weeks in 419 nulliparous and 360 parous women who delivered at term and who underwent 2D and 3D TVS examination of the uterine cervix. We examined approximately 25 women in each gestational week. The length, anteroposterior (AP) diameter and width of the cervix (and of any cervical funnel) and AP diameter of the cervical canal were measured. Results were plotted against gestational age. The agreement between 2D and 3D ultrasound results was expressed as the mean (+/- 2 SDs) difference between the results of the two methods and as the interclass correlation coefficient (inter-CC).

RESULTS

There was excellent agreement between measurements taken by 2D and 3D ultrasound (inter-CC values, 0.80-0.98) but measurements of cervical length taken using 3D ultrasound were greater than measurements taken by 2D ultrasound (mean difference, -0.04 +/- 0.36 cm). Cervical length did not change substantially between 17 and 32 gestational weeks but decreased progressively thereafter. Cervical length was similar in nulliparous and parous women at 17-32 weeks, but from 33 weeks the cervix tended to be longer in parous women. In nulliparae, cervical length decreased from a median of 3.8 (range, 0.7-6.1) cm at 17-32 weeks to 2.3 (range, 0.4-6.0) cm at 33-40 weeks and to 0.7 (range, 0.2-1.5) cm at 41 weeks. In parous women, the corresponding figures were 3.9 (range, 1.0-6.1) cm, 3.0 (range, 0.4-5.7) cm and 0.8 (range, 0.4-3.4) cm (results obtained by 3D ultrasound). Cervical AP diameter and width did not differ between nulliparous and parous women. Median AP diameter increased from 3.0 (range, 2.0-4.6) cm at 17-30 weeks to 3.5 (range, 1.8-5.5) cm at 31-40 weeks and to 4.0 (range, 2.8-5.9) cm at 41 weeks. Cervical width was 3.7 (range, 2.3-6.0) cm at 17-30 weeks and 4.5 (range, 2.3-6.1) cm at 31-41 weeks. The percentage of women with funneling increased from 4% (3/84) at 17-18 weeks to 63% (12/19) at 41 weeks and the percentage of women with an open cervical canal increased from 19% (15/84) to 72% (13/19). Funneling and opening of the cervical canal were equally common in nulliparous and parous women.

CONCLUSIONS

Reference data provide the basis for studies of pathological conditions. Common reference values for nulliparous and parous women can be used for cervical AP diameter and width from 17 to 41 weeks and for cervical length from 17 to 32 weeks. Separate reference values for cervical length for nulliparous and parous women should be used from 33 to 41 weeks.