Transvaginal ultrasonographic evaluation of the cervix before labor: presence of cervical wedging is associated with shorter duration of induced labor

Comparative study Of TVS cervical score and Bishop score in prediction of successful labour induction

Background

In today's obstetric practice, induction of labour is a common procedure. Before the imaging era, the favourability of the cervix was assessed by manual examination scored as the Bishop Score. However, subjectivity and high inter- and intra-observer variability are limitations of this approach. This necessitates the implementation of an objective method of assessment. We used transvaginal sonography (TVS) as an objective method of assessment of cervix by TVS cervical score comprising of five different parameters; cervical length, funnelling at the internal os, distance from the presenting part to the external os, and cervix position. This study aims to evaluate the role of the pre-induction transvaginal ultrasonographic (TVS) cervical score in predicting labour outcome and comparing it to the Bishop score in patients undergoing induction of labour.

Methodology

This observational prospective study included 100 pregnant women admitted for labour induction at a single tertiary care centre. The TVS examination which consisted of five parameters was performed after the clinical Bishop scoring. The TVS scores were compared with the Bishop scores for all patients. Labour induction was done within one hour of examination and the outcome of the induction was recorded.

Results

The mean age was 25.87 years [SD = 4.35]. Labour induction was successful in 74% of patients. At cut-off Scores of ≥ 4, TVS cervical Score performed better than Bishop Score (Sensitivity 93.24 vs. 67.57%, Specificity 73.08 vs. 65.38%). ROC analysis indicated that Area Under Curve (AUC) was more for TVS Score (0.91, 95% CI 0.84–0.97), compared to Bishop Score.

Conclusion

Transvaginal ultrasonography is an objective method of cervical assessment. We conclude from our study that the use of TVS score which consists of five different parameters in cervical assessment provides a better prediction of successful labour induction than the Bishop score, and so can prevent various complications associated with induction failure.

Cervical and Lower Uterine Parameter Ultrasound and Elastographic Parameters for the Prediction of a Successful Induction of Labor

PURPOSE

 The prediction of successful induction of labor (IOL) has been the subject of a series of studies. The predictive role of cervical sonographic and elastographic parameters has been controversially discussed. Lower uterine segment (LUS) thickness and strain values have not been discussed yet in this regard.

MATERIALS AND METHODS

 A prospective cohort study was performed to examine the predictive power of Bishop score parameters, sonographic cervical length (CL), cervical funneling, cervical strain values, LUS thickness and its strain values regarding successful IOL within 24 hours and intervals to onset of labor, ROM and delivery of the fetus. A p-value of < 0.05 was considered statistically significant.

RESULTS

 135 patients were examined. A cervical length of 25 mm, the presence of cervical funneling and digital shorter cervix was significant for the prediction of successful induction of labor (IOL) within 24 hours. There was weak correlation between the functional CL and the onset of labor (r² = 0.10) and ROM (r² = 0.13). There was also a weak correlation between the cervical funnel width and the time interval to the onset of labor (r² = 0.25), ROM (r² = 0.23) and delivery of the fetus (r² = 0.22). Cervical elastography, LUS thickness and strain values were not significant for the prediction of a successful IOL.

CONCLUSION

 We were able to show that cervical structural changes at the level of the internal os, i. e., shortening through funneling, may be the determining factor for successful IOL.

Contribution of ultrasonography to the prediction of the induction-delivery interval: The ECOLDIA prospective multicenter cohort study

INTRODUCTION

To evaluate the ability of preinduction ultrasonographic cervical length to predict the interval between induction and delivery in women at term with a Bishop score of 4 to 6 at induction.

STUDY DESIGN

This multicenter prospective observational cohort recruited 334 women from April 2010 to March 2014. Inclusion criteria were women with singleton pregnancies at a gestational age ≥37 weeks, with no previous caesarean, a medical indication for induction of labor, and a Bishop score of 4, 5, or 6. All women underwent cervical assessment by both transvaginal ultrasound and digital examination (Bishop score). The induction protocol was standardized. The primary outcome measure was the induction-delivery interval. Hazard ratios (HR) and their 95% confidence intervals (95% CI) were used to assess potential predictors.

RESULTS

Mean gestational age at induction was 40.1 weeks, 60.8% of the women were nulliparous, and the cesarean rate was 13.4%. The mean induction-delivery interval was 20.8 h (± 10.6). Delivery occurred within 24 h for 56.9% (n=190) of the women. An ultrasonographic cervical length measurement less than 25 mm (HR=1.50, 95% CI 1.18-1.91, P<0.01) and parity (HR=1.41, 95% CI 1.21-1.65, P<0.01) appeared to predict induction-delivery interval. The cervical length cutoff to reduce the induction-delivery interval was 25 mm.

CONCLUSION

A cervical length cutoff of 25 mm was associated with shorter induction-delivery interval in women at term with a Bishop score of 4 to 6.

Transvaginal two-dimensional ultrasound measurement of cervical volume to predict the outcome of the induction of labour: a prospective observational study

Background

Assessing the likelihood of success of induction of labour using ultrasonically measured cervical volume is an important research question.

Method

A prospective observational study was carried out at North Colombo Teaching Hospital, Ragama, Sri Lanka. Pre-induction digital cervical assessment, transvaginal cervical length, and cervical volume measurements were performed. Inductions with singleton pregnancies at term were included. Basic demographic and clinical details, independent variables (Bishop score, cervical length and cervical volume), and dependent variables (frequency of delivery within 24 h and induction to delivery interval) were recorded. Vaginal delivery within 24 h was the primary outcome.

Results

We studied 100 pregnant women who had induction of labour. Median (IQR) Bishop score was 5 (3–6), mean (SD) cervical length was 3.6 (0.7) cm, and mean (SD) cervical volume was 27.5 (10.4) cm³. Cervical length was the best predictor for predicting the likelihood of vaginal delivery within 24 h [aOR – 12.12 (3.44, 42.71); < 0.001], and cervical volume also appeared to be a significant potential predictor [aOR-1.10 (1.01, 1.17); 0.01]. Cervical length was found to have the highest AUC (0.83) followed by the cervical volume (0.74). The best cut-off value for cervical volume in predicting the likelihood of vaginal delivery within 24 h was less than 28.5 cm³ with a sensitivity of 72% and specificity of 74%.

Conclusions

Transvaginal sonographic measurement of cervical volume appears to be a potential novel predictor for the likelihood of vaginal delivery within 24 h of induction of labour. Cervical length is still more superior to cervical volume in predicting the likelihood of vaginal delivery. Bishop score was not a significant predictor in this context.

The Cervicovaginal Mucus Barrier

Preterm births are a global health priority that affects 15 million babies every year worldwide. There are no effective prognostic and therapeutic strategies relating to preterm delivery, but uterine infections appear to be a major cause. The vaginal epithelium is covered by the cervicovaginal mucus, which is essential to health because of its direct involvement in reproduction and functions as a selective barrier by sheltering the beneficial lactobacilli while helping to clear pathogens. During pregnancy, the cervical canal is sealed with a cervical mucus plug that prevents the vaginal flora from ascending toward the uterine compartment, which protects the fetus from pathogens. Abnormalities of the cervical mucus plug and bacterial vaginosis are associated with a higher risk of preterm delivery. This review addresses the current understanding of the cervicovaginal mucus and the cervical mucus plug and their interactions with the microbial communities in both the physiological state and bacterial vaginosis, with a focus on gel-forming mucins. We also review the current state of knowledge of gel-forming mucins contained in mouse cervicovaginal mucus and the mouse models used to study bacterial vaginosis.

The Effect of Ultrasound-Measured Preinduction Cervical Length on Delivery Outcome in a Low-Resource Setting

Background

Induction of labour is not without risk, and it calls for a method that will be sensitive enough to predict successful labour induction.

Aim

This study aims to evaluate the role of transvaginal ultrasonographic cervical length measurement at term in the prediction of successful induction of labour (IOL).

Materials and Methods

This prospective study was carried out in the Department of Obstetrics and Gynaecology of Federal Teaching Hospital Abakaliki between 1st of July and 30^th of November 2015. Preinduction Bishop score and cervical length were assessed before induction of labour. Intracervical, cervical, extraamniotic Foley catheter was used to improve the Bishop score. The data were analyzed using the IBM SPSS Statistics 20.

Results

The mean maternal age of the study group was 30.68 ± 6.38 years with a range of 19–43 years. The mean gestational age and parity were 39.57 ± 1.49 and 1.85 ± 0.63, respectively. All the women studied had successful induction of labour with mean induction delivery time of 8.1 ± 3.0 hours and mean duration of labour of 7.4 ± 2.9 hours. Preinduction cervical length is a good predictor of a short duration of labour (P = 0.001). Parturient with a preinduction cervical length of less than 3 cm was likely to have labour lasting less than 6 hours (RR = 4.20 (95% CI 1.85–9.529).

Conclusion

Transvaginal sonographic measurement of cervical length provides a useful prediction of the likelihood of duration of labour following the induction of labour. It is recommended that IOL should be considered and success anticipated in a parturient with a cervical length less than 3 cm.

Transvaginal sonographic measurement of cervical length versus Bishop score in labor induction at term for prediction of caesarean delivery

OBJECTIVE

The current study aims to compare between a transvaginal sonographic measurement of cervical length and Bishop score in the induction of labor (IOL) at term for prediction of cesarean delivery (CD).

MATERIALS AND METHODS

A prospective cohort study included 320 full-term pregnant women attending Ain Shams Maternity Hospital in the period from August 2017 to February 2018 were enrolled. Seventy-three women were delivered by CD (positive group), and 247 women were delivered vaginally (negative group). All patients had a vaginal examination for assessing the Bishop Score before IOL then a transvaginal ultrasound for assessment of cervical length. IOL was initiated by using PGE1 analog. The primary outcome measure was the accuracy of the cervical length or the bishop score for prediction of the CD.

RESULTS

In our current study, CD was achieved in 22.8% of all participants while vaginal delivery was achieved in 77.8% after IOL by misoprostol 25 micrograms within 24 h from the beginning of induction. Both the cervical length and Bishop Score had poor predictive value for CD (AUC = 0.694 and 0.623, respectively).

CONCLUSIONS

Both transvaginal sonography for cervical length and Bishop score are useful predictors of the need for CD following labor induction.

Labor Induction Techniques: Which Is the Best?

Induction of labor is a common procedure undertaken whenever the benefits of prompt delivery outweigh the risks of expectant management. Cervical assessment is essential to determine the optimal approach. Indication for induction, clinical presentation and history, safety, cost, and patient preference may factor into the selection of methods. For the unfavorable cervix, several pharmacologic and mechanical methods are available, each with associated advantages and disadvantages. In women with a favorable cervix, combined use of amniotomy and intravenous oxytocin is generally the most effective approach. The goal of labor induction is to ensure the best possible outcome for mother and newborn.

[The opening of the internal cervical os predicts cervical ripening better than Bishop's score in nulliparous women at 41 weeks gestation]

Introduction

L'objectif était d'évaluer la mesure échographique de l’ouverture de l’orifice interne du col dans la prédiction de l’issue de la maturation cervicale et la comparer au Score de Bishop.

Méthodes

Nous avons mené une étude prospective sur 10 mois, entre Juillet 2012 et avril 2013 colligeant 77 femmes nullipares admises pour déclenchement du travail à un terme de 41 SA avec un Score de Bishop < 6. La mesure de l’ouverture de l’orifice interne du col a été réalisée par échographie transvaginale et le score de Bishop a été déterminé par l'examen clinique. Toutes les patientes ont eu une maturation cervicale par des prostaglandines.

Résultats

La maturation cervicale était réussie chez 63 patients (81%). Le Score de Bishop et l’ouverture de l’orifice interne du col se sont révélés statistiquement associés au succès ou l’échec de la maturation cervicale. Le taux de succès de la maturation était de 100% lorsque l’ouverture de l’orifice interne du col était égale ou supérieure à 5 mm (sensibilité: 54%; spécificité: 86%). Les courbes ROC ont montré que la mesure de l’orifice interne du col était plus prédictive de l’issue de la maturation cervicale que le Score de Bishop (Aire sous la courbe respectivement 0.733 et 0.704).

Conclusion

Comparée au score de Bishop, la mesure échographique de l’ouverture de l’orifice interne du col est plus prédictive du succès de la maturation cervicale chez les femmes nullipares à 41 semaines d’aménorrhée avec un col défavorable.

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.

Successful induction of labor: prediction by preinduction cervical length, angle of progression and cervical elastography

OBJECTIVE

To examine the potential value of preinduction cervical length, cervical elastography and angle of progression (AOP) in prediction of successful vaginal delivery and induction-to-delivery interval.

METHODS

This was a prospective study in 99 women with singleton pregnancy undergoing preinduction ultrasound assessment at 35-42 weeks' gestation. Cervical length, elastographic score at the internal os and AOP were determined. Regression analysis was used to assess the relationship between cervical length and both AOP and elastographic score. Logistic regression analysis was used to determine which of the maternal characteristics (cervical length, AOP, elastographic score) were significant predictors of vaginal delivery and induction-to-delivery interval.

RESULTS

Vaginal delivery occurred in 66 (66.7%) cases and Cesarean delivery was performed in 33 (33.3%) cases. There were significant correlations between cervical length and both AOP (r = - 0.319) and elastographic score (r = 0.368). Significant independent prediction of vaginal delivery and induction-to-delivery interval was provided by nulliparity and cervical length, with no additional significant contribution from electrographic score or AOP.

CONCLUSIONS

In women undergoing induction of labor, AOP and elastographic score at the internal os are unlikely to be useful in prediction of vaginal delivery and induction-to-delivery interval.

Can measurement of cervical length, fetal head position and posterior cervical angle be an alternative method to Bishop score in the prediction of successful labor induction?

AIM

The purpose of this study was to evaluate sonographic cervical length, posterior cervical angle and fetal head position in predicting successful induction of labor at term can be an alternative method to Bishop score.

METHODS

This prospective observational study recruited 223 women with singleton gestations scheduled for induction of labor at 37-42 weeks. Parity, body mass index, Bishop score, fetal head position, cervical angle measurement and cervical length was investigated to predict successful labor induction. Multiple regression analysis was performed to determine the parameters in the prediction of successful vaginal delivery within 24 hours.

RESULTS

Forty-five patients were excluded because of cesarean section performed for other reasons than arrest of dilation or fetal head descent (43 fetal distress, 2 cord prolapsus). Remaining 178 patients were divided into two groups according to duration of delivery time. 139 patients delivered within 24 hours were classified as group I, 39 patients delivered after 24 hours were classified as group II. Percentage of multiparity was statistically significantly higher in group I than in group II [59 (42.4%), 9 (23.0%) respectively, p = 0.009]. Cervical length was statistically significantly shorter in group I than in group II [23.1 ± 7.42 mm, 31.3 ± 6.83 mm respectively, p < 0.001]. Bishop score was statistically significantly higher in group I than in group II [3 (1-4), 1 (1-4) respectively, p < 0.001]. Posterior cervical angle was statistically significantly higher in group I than in group II [100.1 ± 17.2, 92.7 ± 21.4 respectively, p = 0.007]. According to the fetal head position, there was no statistically significant difference in labor duration between the groups (p = 0.787). In the multivariate regression analysis of variables, multiparity, cervical length and Bishop score were statistically significantly predictive in successful labor induction.

CONCLUSION

Multiparity status, cervical length, posterior cervical angle and Bishop score can predict successful labor induction, but fetal head position is not predictive in successful labor induction.

Sonoelastography as method for preliminary evaluation of uterine cervix to predict success of induction of labor

INTRODUCTION

Induction of labor is a useful practice to solve many obstetric situations but has a large impact on the health of women and their babies and therefore needs to be clearly justified clinically.

AIM

To determine the sensitivity of sonoelastography in the evaluation of the cervix to predict the success of induction.

MATERIALS AND METHODS

We enrolled 53 subjects preparing for induction of labor. Transvaginal evaluation of cervical length and a sonoelastogram were performed. We preliminarily classified the sonoelastograms into five elastography index (EI) categories and examined the different distribution of cesarean or spontaneous deliveries in various subgroups of EI by χ(2) test and multivariate analysis by logistic regression.

RESULTS

Statistical analysis revealed a significant difference of prevalence of spontaneous delivery (EI1-3 82.75%, EI4-5 45.8%) versus cesarean section (EI1-3 17.25%, EI4-5 54.16%) (p = 0.0072). The diagnostic validity of EI was evaluated using the receiver operating characteristic curve and cut-off of the predictive value was EI3.

DISCUSSION

The results of our study indicate that sonoelastography is an innovative technique that could allow a more objective preliminary evaluation of the cervix before inducing labor, however further studies with a larger number of subjects and a standardization of image acquisition are necessary.

Transvaginal sonographic assessment of cervical length and wedging for predicting outcome of labor induction at term: a systematic review and meta-analysis

OBJECTIVE

To perform a systematic review and meta-analysis to assess the predictive capacity of transvaginal sonographic assessment of the cervix for the outcome of induction of labor.

METHODS

We searched MEDLINE, EMBASE and the Cochrane Library, and manually searched reference lists of review articles and eligible primary articles. Studies in all languages were eligible if published in full. Two reviewers independently selected studies and extracted data on study characteristics, quality and test accuracy. We then calculated pooled sensitivities and specificities (with 95% CIs) and summary receiver-operating characteristics (sROC) curves. Outcome measures were test accuracy of sonographically measured cervical length and cervical wedging for Cesarean section, not achieving vaginal delivery within 24 h and not achieving active labor.

RESULTS

We included 31 studies reporting on both cervical length and outcome of delivery. The quality of the included studies was mediocre. Sensitivity of cervical length in the prediction of Cesarean delivery ranged from 0.14 to 0.92 and specificity ranged from 0.35 to 1.00. The estimated sROC curve for cervical length indicated a limited predictive capacity in the prediction of Cesarean delivery. Summary estimates of sensitivity/specificity combinations of cervical length at different cut-offs for Cesarean delivery were 0.82/0.34, 0.64/0.74 and 0.13/0.95 for 20, 30 and 40 mm, respectively. For cervical wedging in the prediction of failed induction of labor summary point estimates of sensitivity/specificity were 0.37/0.80.

CONCLUSIONS

Cervical length and cervical wedging as measured sonographically at or near term have moderate capacity to predict the outcome of delivery after induction of labor.

Prediction of successful labor induction using transvaginal sonographic cervical measurements

PURPOSE

To predict the success of labor induction by sonographic cervical measurements, maternal/obstetrical factors, and the Bishop's score.

METHODS

Between February 2008 and February 2010, 190 consecutive pregnant women underwent clinical examination to assess the Bishop's score and transvaginal sonographic cervical measurements (cervical length, fetal head stage, and cervical dilatation) before labor induction. The following outcomes were analyzed: overall vaginal delivery and vaginal delivery up to 24 hours after labor induction.

RESULTS

Overall vaginal delivery occurred in 133 (70.0%) patients and vaginal delivery 24 hours after labor induction happened in 119 (62.6%) patients. The sonographic cervical measurements were significantly associated with all outcomes (p < 0.01). The areas under the ROC curve (AUC) of all ultrasound cervical parameters to predict the two events were 68.9% and 72.0% (cervical length); 71.6% and 73.6% (fetal head stage); and 72.0% and 73.4% (cervical dilatation). Mathematical equations were obtained to calculate the probability for each event considering the sonographic cervical measurements in association with clinical factors after regression analysis, which increased the AUC for both events (80.1% and 79.3%).

CONCLUSIONS

Transvaginal sonographic cervical measurements can predict the successful labor induction, especially when associated to clinical analysis (Bishop's score).

Validation of models that predict Cesarean section after induction of labor

OBJECTIVE

Models for the prediction of Cesarean delivery after induction of labor can be used to improve clinical decision-making. The objective of this study was to validate two existing models, published by Peregrine et al. and Rane et al., for the prediction of Cesarean section after induction of labor.

METHODS

We studied consecutive women in whom labor was induced. In all women, we recorded maternal age, height, body mass index, parity, gestational age and the Bishop score prior to induction. Cervical length was measured by transvaginal ultrasound immediately prior to induction of labor. The primary end-point was delivery by Cesarean section. The calibration of the two prediction models was assessed by comparison of predicted and observed Cesarean delivery rates. The discriminative capacity of the models, i.e. the ability of the models to distinguish subjects who had Cesarean section from those who did not (discrimination), was assessed by receiver-operating characteristics (ROC) analysis.

RESULTS

We included 240 women in the study, of whom 27 (11%) had Cesarean delivery. The capacity of cervical length in the prediction of Cesarean delivery was limited. In our study population, both prediction models overestimated the risk of Cesarean delivery. Calibration was better for the Peregrine et al. model than for the Rane et al. model, and the two models had areas under the ROC curve of 0.76 and 0.67, respectively.

CONCLUSION

Current models that predict the occurrence of Cesarean section after induction of labor have only a moderate predictive capacity when applied within a Dutch practice. We do not recommend the use of these prediction models in clinical practice.

Comparison between subjective and objective assessments of the cervix before induction of labour

The aim of the study was to compare the pre-induction cervical assessment by Bishop's score with the transvaginal ultrasound cervical length as predictors of the induction-delivery interval (IDI) and the success of induction. This prospective study included 104 women with singleton pregnancies who were booked for induction of labour at term over a period of 3 years. Transvaginal ultrasound measurement of the cervical length and Bishop's Score were performed by different operators. Data were collected on parity, gestational age, methods of induction, Bishop's score, ultrasound cervical length measurements, IDI and mode of delivery. A total of 87 women (83.7%) delivered vaginally and 17 (16.3%) delivered by caesarean section. Linear regression models demonstrated that ultrasound cervical length was a better indicator of IDI than Bishop's score. The adjusted R2 for the regression including ultrasound cervical length was 0.87 compared with a value of 0.67 for the model including Bishop's score. Although logistic regression analysis confirmed that cervical effacement was the best component of Bishop's score to predict the mode of delivery, ultrasound cervical length assessment provided better prediction. Receiver operating characteristic curve showed that the optimised cut-off value for prediction of vaginal delivery was < or =3.4 cm for the cervical length and >5 for the Bishop's score. At those optimised cut-off values the cervical length predicted vaginal delivery with sensitivity of 62.1% (95% CI [51%, 72.3%]) and specificity of 100% (95% CI [80.5%, 100%]) while the Bishop's score predicted vaginal delivery with a sensitivity of 23% (95% CI [14.6%, 33.2%]) and specificity of 88.2% (95% CI [63.5%, 98.5%]). Further analysis showed that ultrasound cervical length has a higher sensitivity in prediction of vaginal delivery in multiparous than nulliparous women (85.1% compared with 35%) at a cut-off value of < or =3.4 cm. On the other hand, it has a higher sensitivity in nulliparous comparable with multiparous women (85.3% compared with 30%) in prediction of IDI at a cut-off value of >3.5 cm. In conclusion, transvaginal ultrasound cervical length assessment is better than Bishop's score in predicting the IDI and the success of induction of labour.

Transvaginal ultrasound measurement of cervical length in the supine and upright positions versus Bishop score in predicting successful induction of labor at term

OBJECTIVES

To examine the predictive value of cervical length as measured by transvaginal sonography (TVS) in supine and upright maternal positions for the mode of delivery and induction-to-delivery interval after induction of labor at term, and to compare these measurements with the Bishop score and its predictive value.

METHODS

TVS for cervical length measurement in the supine and upright positions and digital examination of the cervix were performed in 68 nulliparous and 34 parous women before induction of labor at term. In assessing the predictive value of the Bishop score and TVS parameters for a vaginal delivery after labor induction only nulliparous women were included in the analysis, since all the parous women delivered vaginally. Both nulliparous and parous women were included in the analysis of the induction-to-delivery interval. The method of labor induction, oxytocin or prostaglandin, was determined on the basis of the pre-induction Bishop score.

RESULTS

Logistic regression analysis showed in nulliparous women that only the cervical length measured in the upright position was a significant predictor of the need for Cesarean section (odds ratio 1.14; 95% CI, 1.02-1.27). The areas under the receiver-operating characteristics curve in predicting the need for Cesarean section because of failure to progress were higher for the cervical length, both in supine and upright positions, than for the Bishop score (0.66, 0.68 and 0.46, respectively). Only the Bishop score correlated significantly with the induction-to-delivery interval in both nulliparous and parous women. However, this may have been due to a selection bias, as no significant correlation with Bishop score was found when the oxytocin and prostaglandin induction-to-delivery intervals were analyzed separately.

CONCLUSION

Our results suggest that maternal postural change might improve the accuracy of sonographically-measured cervical length for predicting a vaginal delivery after induction of labor at term. However, our results need to be confirmed in a larger and more homogeneous population.

Beyond neuroanatomy: novel approaches to studying brain evolution

The study of the evolution of brain structure and function, although fascinating, has been contentious, largely due to the correlative nature of neuroanatomical comparisons and the often ill-defined categorizations of habitat and behavior. We outline four conceptual approaches that will help the field of brain evolution emerge from a historical focus on descriptive comparative neuroanatomy. First, reliable, efficient and unbiased behavioral assays must be developed to characterize relevant cross-species differences in addition to focused studies of neuroanatomy. Second, developmental and physiological processes underlying neuroanatomical and behavioral differences can be analyzed using the comparative approach. Third, genome-wide comparisons including genome-wide linkage mapping, transcriptional profiling, and direct sequence comparisons, can be applied to identify the genetic basis for phenotypic differences. Finally, signatures of selection in DNA sequence can provide clues about adaptive genetic changes that affect the nervous system. These four approaches, which all depend on well-resolved phylogenies, will build on detailed neuroanatomical studies to provide a richer understanding of mechanistic and selective factors underlying brain evolution.

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.

Sonographic cervical assessment to predict the success of labor induction: a systematic review with metaanalysis

OBJECTIVE

The purpose of this investigation was to review the literature that evaluates sonographic cervical assessment to predict successful induction of labor.

STUDY DESIGN

Published prospective trials that measured sonographic cervical length before labor induction was initiated were evaluated. Trials were excluded if they contained data presented in later articles or did not contain extractable data. The total analysis included 20 trials with 3101 aggregate participants.

RESULTS

Cervical length predicted successful induction (likelihood ratio of positive test, 1.66; 95% confidence interval [CI], 1.20-2.31) and failed induction (likelihood ratio of negative test, 0.51; 95% CI, 0.39-0.67). Cervical length did not predict any specific outcome (eg, mode of delivery). The assessment of cervical wedging proved to be a useful diagnostic test, with a likelihood ratio of a positive test result of 2.64 and a likelihood ratio of a negative test result of 0.64.

CONCLUSION

Sonographic cervical length was not an effective predictor of successful labor induction. Further evaluation of cervical wedging in the prediction of labor induction appears warranted.

Transvaginal ultrasonographic cervical measurement in predicting failed labor induction and cesarean delivery for failure to progress in nulliparous women

The aim of this study was to evaluate the value of transvaginal sonographic cervical measurement in predicting failed labor induction and cesarean delivery for failure to progress in nulliparous women. One hundred and sixty-one women scheduled for labor induction underwent transvaginal ultrasonography and digital cervical examinations. Logistic regression demonstrated that cervical length and gestational age at induction, but not the Bishop score, significantly and independently predicted failed labor induction. According to the receiver operating characteristic curves analysis, the best cut-off value of cervical length for predicting failed labor induction was 28 mm, with a sensitivity of 62% and a specificity of 60%. In terms of the likelihood of a cesarean delivery for failure to progress as the outcome variable, logistic regression indicated that maternal height and birth weight, but not cervical length or Bishop score, were significantly and independently associated with an increased risk of cesarean delivery for failure to progress. Transvaginal sonographic measurements of cervical length thus independently predicted failed labor induction in nulliparous women. However, the relatively poor predictive performance of this test undermines its clinical usefulness as a predictor of failed labor induction. Moreover, cervical length appears to have a poor predictive value for the likelihood of a cesarean delivery for failure to progress.

The labor induction: integrated clinical and sonographic variables that predict the outcome

OBJECTIVE

To analyze the clinical and sonographic variables that predicts the success of labor induction.

STUDY DESIGN

We studied the Bishop score, cervical length and parity in 196 pregnant women in the prediction of successful vaginal delivery within 24 h of induction. Logistic regression and segmentation analysis were performed.

RESULTS

Cervical length (odds ratio (OR) 1.089, P<0.001), Bishop score (OR 0.751, P=0.001) and parity (OR 4.7, P<0.001) predict the success of labor induction. In a global analysis of the variables studied, the best statistic sequence that predicts the labor induction was found when we introduced parity in the first place. The success of labor induction in nulliparous was 50.8 and 83.3% in multiparous women (P=0.0001).

CONCLUSIONS

Cervical length, Bishop score and parity, integrated in a flow chart, provide independent prediction of vaginal delivery within 24 h of induction.

Preinduction Cervical Assessment

The rate of labor induction is increasing in the United States. Methods for quantifying cervical factors have been developed to identify patients who may benefit from cervical ripening before induction. The first cervical scoring systems used digital examination. More recently, cervical ultrasound and testing for the presence of fetal fibronectin have been suggested to evaluate cervical readiness for labor induction, but neither of these methods provides a significant improvement over digital examination. The Bishop score, the most widely used digital examination scoring system, still is the most cost effective and accurate method of evaluating the cervix before labor induction.

Clinical and Ultrasound Parameters to Predict the Risk of Cesarean Delivery After Induction of Labor

OBJECTIVE

To evaluate whether factors in the maternal history and/or ultrasound parameters are useful in predicting the risk of cesarean delivery after induction of labor.

METHODS

Maternal age, height, body mass index, parity, gestational age, Bishop score, ultrasonic amniotic fluid volume, fetal head position, estimated fetal weight, and transvaginal cervical length were studied prospectively in 267 women at 36 or more weeks of gestation immediately before induction of labor. Logistic regression analysis was used to determine which factors best predicted the risk of cesarean delivery. Receiver operating characteristic curves and a resampling technique were used to evaluate the model's performance.

RESULTS

Eighty (30%) of these 267 women had cesarean delivery. Logistic regression was performed and a final model chosen, which included parity (odds ratio [OR] 20.56, 95% confidence interval [CI] 7.97-53.05, P < .001), body mass index (OR 6.17, 95% CI 2.10-18.13, P < .001), height (OR 0.94, 95% CI 0.89-0.98, P = .005), and ultrasonic transvaginal cervical length (OR 1.07, 95% CI 1.04-1.11, P < .001) as the best predictors of cesarean delivery. A risk score was calculated containing these 4 parameters, which predicted reasonably accurately the risk of cesarean delivery.

CONCLUSION

Parity, body mass index, height, and ultrasonic transvaginal cervical length are the most accurate parameters in predicting the risk of cesarean delivery after induction of labor. A predictive model using these would allow more accurate counseling and better informed consent in the decision-making process regarding induction of labor

LEVEL OF EVIDENCE

II-2.

Sonographic cervical length measurement before labor induction in term nulliparous women

OBJECTIVE

The purpose of the study was to determine if transvaginal sonographic measurement of the cervical length is a useful method to predict successful labor induction in nulliparas.

METHODS

137 women who were scheduled for medically indicated induction of labor had a transvaginal sonographic measurement of the cervical length before labor induction. Inclusion criteria were: (1) singleton pregnancy; (2) gestational age between 37-42 weeks; (3) live fetus in cephalic presentation; (4) intact membranes; (5) no vaginal bleeding; (6) no previous history of uterine surgery; (7) nulliparous women, and (8) no allergy or asthma in response to prostaglandins. Induction of labor was performed within 6 h of the ultrasonographic examination, by inserting 2 mg of dinoprostone in the posterior vaginal fornix, repeated if needed every 6 h for up to three doses. When the cervix became favorable and no regular contractions were observed, amniotomy and oxytocin augmentation, starting at 1 mIU/min and increasing 1 mIU every 30 min as necessary, was performed.

RESULTS

All women were Caucasians and the mean age was 24.3 years (range 19-37 years). The mean cervical length was 28 mm (range 11-39 mm). The Bishop score was < or =5 in 101 women and >5 in the 36 others. Vaginal delivery occurred in 92 women (67.1%), and the vast majority of them (89 women; 96.7%) gave birth within 24 h of induction. Forty-five women (32.8%) had a cesarean section. The Bishop score was not predictive of the mode of delivery. Thirty-six of 101 women (35.6%) with a Bishop score < or =5 delivered by cesarean section, compared to 9 of 36 women with a Bishop score >5 (25%) (p = NS). Women with a cervical length <27 mm were more likely to deliver vaginally. Using this cutoff value the sensitivity of a successful labor induction was 76% and the specificity was 75.5%.

CONCLUSIONS

Transvaginal sonographic measurement of cervical length is a good predictor of a successful labor induction at term in nulliparas.

Variables that predict the success of labor induction

BACKGROUND

To analyze the clinical and sonographic variables that affect the success of labor induction.

METHODS

Bishop score, cervical length, and parity were studied in 196 pregnant women in the prediction of successful vaginal delivery within 24 hr of induction. Logistic regression and segmentation analysis were performed.

RESULTS

Cervical length [odds ratio (OR) 1.089, P<0.001], Bishop score (OR 0.751, P=0.001), and parity (OR 6.85, P<0.001) predict the success of labor induction. The best cut-off points for cervical length were <16.5, 16.5--27, and >27 mm (P=0.0016). In the analysis of the Bishop score, we also obtained three discriminatory points, 0, 1--4, and >4 (P=0.0006), that best predict the labor induction. Finally, in a global analysis of the variables studied, the best statistic sequence that predicts the labor induction was found when we introduced parity in the first place. The success of labor induction in nulliparous was 50.77 and 83.33% in multiparous (P=0.0001).

CONCLUSIONS

Cervical length, Bishop score, and parity predict the success of labor induction.

Bishop score and transvaginal ultrasound for preinduction cervical assessment: a randomized clinical trial

OBJECTIVE

To compare transvaginal ultrasound with the Bishop score in assessment of cervical ripening for choice of induction agent.

METHODS

Eighty women were randomized to have preinduction cervical assessment for choice of induction agent based on either Bishop score or transvaginal ultrasound. The primary outcome measure was the percentage of women who were administered prostaglandin as a preinduction agent. The criteria for considering the cervix as unripe and thus for using prostaglandin were either a Bishop score < 6 or a cervical length > 30 mm with cervical wedging of < 30% of the total cervical length. Secondary outcome measures included interval to active phase, interval to delivery and rate of Cesarean section.

RESULTS

While 85% of women received prostaglandin in the Bishop score group, only 50% of them did in the transvaginal ultrasound group (P = 0.001). The interval to active phase, interval to delivery and rate of Cesarean section were similar in both groups.

CONCLUSIONS

With the suggested cut-off values of a Bishop score < 6 or a cervical length > 30 mm and wedging < 30%, the use of transvaginal ultrasound instead of Bishop score for preinduction cervical assessment to choose induction agent significantly reduces the need for intracervical prostaglandin treatment without adversely affecting the success of induction.

Comparison of digital and ultrasonographic examination of the cervix in predicting time interval from induction to delivery in women with a low Bishop score

OBJECTIVE

To compare pre-induction ultrasonographic cervical length and Bishop score in predicting time to delivery after labour induction with prostaglandins.

DESIGN

Prognostic cohort study.

SETTING

Tertiary referral maternity unit in a teaching hospital.

POPULATION

Two hundred and sixty-six women with singleton pregnancies at between 34(+0) and 41(+3) weeks of gestation requiring induction of labour with prostaglandins for medical indications.

METHODS

A secondary analysis of a trial comparing two prostaglandins. Assessment of the Bishop score and measurement of the cervical length by transvaginal sonography were performed by two operators, blinded to each other's results. We estimated the predictive effects on the outcomes of ultrasonographic cervical length and Bishop score.

MAIN OUTCOME MEASURE

Time intervals from induction to delivery and to vaginal delivery.

RESULTS

Cervical length and Bishop score were associated with the time interval from induction to delivery, based on univariable analyses. When considered jointly in a multivariable model, only the Bishop score was significantly related to the outcome: The higher the Bishop score, the higher the hazard to delivery [hazard ratio (HR): 1.2, 95% confidence interval (CI): 1.1-1.3], illustrating that once the Bishop score is taken into account, further knowledge of cervical ultrasound length (HR: 0.99, 95% CI: 0.98-1.0) did not add any predictive information. Also, Bishop score was predictive of time interval between induction and vaginal delivery (HR: 1.2, 95% CI: 1.1-1.4) while cervical length had no additional predictive value (HR: 0.99, 95% CI: 0.98-1.0) when both cervical length and Bishop score were introduced in the model.

CONCLUSIONS

The Bishop score appears to be a better predictor of the time interval from induction to delivery and to vaginal delivery than cervical length after induction of labour for medical reasons.

Comparaison du score de Bishop et de la mesure échographique de la longueur du col dans la prédiction du risque de césarienne avant maturation du col par prostaglandines

OBJECTIVE

To compare pre-induction ultrasonographic cervical length and Bishop score in predicting risk of caesarean section after labor induction with prostaglandins.

PATIENTS AND METHODS

Assessment of the Bishop score and measurement of the cervical length by transvaginal sonography were performed by two operators, blinded to each other's results among women with singleton pregnancies at between 34(+0) - 41(+3) weeks of gestation requiring induction of labor with prostaglandins for medical indications. Fisher's exact test and regression logistic models were used for statistics analysis. In order to measure the strength of the association between ultrasonographic cervical length or Bishop score on one hand, and the caesarean sections rate (global or for failed induction or failure to progress) on the other hand, we computed odds ratios with 95% confidence interval.

RESULTS

Among the 266 patients included in the study, multivariate analysis has shown that only Bishop score was predictive for the global caesarean section risk (OR [95% CI] 0.63 [0.45-0.87] ; P =0.005). However, neither Bishop score (OR [95% CI] 0.68 [0.42-1.09] ; P =0.11), nor ultrasonographic cervical length (OR [95% CI] 1.01 [0.95-1.08] ; P =0.59) was predictive for failed induction or failure to progress caesarean section risk.

DISCUSSION AND CONCLUSION

The Bishop score appears to be a better predictor of the global caesarean section risk than ultrasonographic cervical length after induction of labor for medical reasons.

The role of ultrasound and fetal fibronectin in predicting the length of induced labor when the cervix is unfavorable

OBJECTIVE

To compare cervical clinical data, ultrasound parameters and fetal fibronectin assessment in the prediction of the duration of induced labor when the cervix is unfavorable.

METHODS

This was a prospective study of 90 pregnant women with a Bishop score </= 5 undergoing labor induction. The Bishop score and its components, parity, cervical ultrasound parameters and fetal fibronectin level were analyzed using Cox's model in order to determine the most predictive factors for the duration of the latent and active phases of labor as well as its total duration.

RESULTS

There was a significant correlation between duration of the latent phase and the whole of labor, and digitally assessed cervical dilatation (P = 0.003 and P < 0.001, respectively), parity (P = 0.006 and P < 0.001), the Bishop score (P = 0.019 and P = 0.003) and ultrasound-determined cervical length (P = 0.035 and P = 0.003). The length of the active phase of labor did not correlate with the cervical status. Funneling did not appear to be predictive of the duration of labor and it had a poor correlation with digital cervical dilatation. The length of the latent phase and that of the whole of labor was significantly longer when cervical dilatation was </= 2 cm (P < 0.001 in each case), when women were nulliparous (P = 0.002 and P < 0.001) and when ultrasound cervical length was >/= 27 mm (P = 0.002 and P = 0.005).

CONCLUSION

Cervical dilatation as assessed by digital examination is the best predictor of the duration of the latent phase and of that of the whole of labor. Ultrasound measurement of cervical length is not more accurate at predicting the duration of labor than are clinical data.

Does ultrasound examination when the cervix is unfavorable improve the prediction of failed labor induction?

OBJECTIVE

To compare the Bishop score, ultrasound cervical parameters and fetal fibronectin assessment for predicting failed labor induction when the cervix is unfavorable.

METHOD

A prospective observational study was performed in 106 consecutive pregnant women with a Bishop score < or =5 undergoing labor induction. Assessment of fetal fibronectin and ultrasound measurement of cervical length, cervical wedging and cervical lip areas were performed. The relationship between these parameters and failure of labor induction was determined.

RESULTS

Failure of labor induction was defined as failure to reach a cervical dilatation of > or =5 cm, and it occurred in 16 patients (15.1%). Induction failure was associated with low Bishop scores before (P = 0.004) and 6 h after the start of induction (P = 0.007), increased clinical cervical length (P = 0.02) and increased ultrasound anterior cervical lip area (P = 0.04). The logistic regression model identified the Bishop score before induction (odds ratio = 2.25; 95% CI, 1.30-3.91; P = 0.003) and the clinical cervical length (odds ratio = 3.95; 95% CI, 1.3-11.7; P = 0.01) as being independent predictors of failed induction. To predict an induction failure, the best Bishop score cut-off value was 4, with a sensitivity of 87.5%, a specificity of 45.6%, a likelihood ratio of 1.58, a positive predictive value of 22.2% and a negative predictive value of 95.4%.

CONCLUSION

Compared with the Bishop score, cervical length by ultrasound is not a better predictor for the outcome of labor induction in an unfavorable cervix. Nevertheless, the Bishop score appears to be of poor predictive value for failed induction of labor.

Transvaginal ultrasonography for cervical assessment before induction of labor

OBJECTIVE

To evaluate the value of ultrasonographic cervical assessment in predicting the outcome of labor induction and to compare its performance against the Bishop score.

METHODS

The Bishop score was determined by digital examination, and transvaginal ultrasonography was performed in 105 women at 37 to 42 weeks' gestation scheduled for labor induction. Ultrasonographic parameters evaluated were cervical length, the presence of funneling, funnel width, and funnel length and were blinded to managing physicians. The primary outcome was the occurrence of active labor within 2 days (successful labor induction). The interval from the onset of induction to active labor (duration of induction) was the secondary outcome. Statistical analysis was performed by the chi2 test, Wilcoxon rank sum test, Pearson correlation, receiver operating characteristic curves, logistic regression, Cox proportional hazards model, and generalized Wilcoxon test for survival data.

RESULTS

Induction of labor was successful in 93 women (89%). The area under the receiver operating characteristic curve for cervical length was greater than that of the Bishop score in predicting a successful labor induction (z = 2.18; P < .05). A cervical length of 3.0 cm or less had sensitivity of 75% (70 of 93) and specificity of 83% (10 of 12). Multiple logistic regression analysis showed a significant relationship between successful labor induction and cervical length but not the Bishop score (odds ratio = 0.24; 95% confidence interval, 0.096-0.59; P = .002). Only parity and cervical length had a significantly independent relationship with the duration of induction.

CONCLUSIONS

Cervical length measured by transvaginal ultrasonography is a useful and independent predictor of successful labor induction and the duration of induction and provides better predictability of successful labor induction than the Bishop score does.

Prediction of successful induction of labor at term: role of clinical history, digital examination, ultrasound assessment of the cervix, and fetal fibronectin assay

OBJECTIVE

The purpose of this study was to evaluate whether biochemical (fetal fibronectin assay) or biophysical (cervical assessment by transvaginal ultrasound) tests may have more value than digital examination in predicting successful induction of labor at term.

STUDY DESIGN

The study enrolled prospectively 134 women undergoing labor induction at term caused by several obstetric conditions. All participants submitted to digital examination, fetal fibronectin assay, and transvaginal ultrasound for measurement of the cervical length and detection of funneling. The performance of each test in predicting delivery within 24 hours of labor induction was evaluated. Cox multiple regression analysis was performed to identify, among clinical and laboratory tests, which variables were independently associated with the duration of the latent phase and with the total duration of induced labor.

RESULTS

The likelihood ratios for positive results (predicting that delivery would occur within 24 hours) were 6.61 (95% CI, 1.7-25.8) for a positive obstetric history (previous vaginal delivery), 2.61 (95% CI, 1.6-4.3) for a "favorable" digital examination, 1.41 (95% CI, 0.9-2.2) for a positive fetal fibronectin test, 1.61 (95% CI, 0.9-3.0) for cervical length, and 2.20 (95% CI, 1.1-4.4) for the presence of funneling at transvaginal ultrasound. The likelihood ratios for negative results were 1.81 (1.3-2.5) for obstetric history, 4.34 (2.5-7.7) for digital examination, 1.41 (0.9-2.1) for fetal fibronectin, 1.29 (1.0-1.7) for cervical length, and 1.48 (1.1-2.0) for funneling. On multiple regression, the only variables independently associated with the duration of the latent phase and with the total duration of induced labor were obstetric history and digital examination.

CONCLUSION

Only obstetric history and digital examination predicted accurately vaginal delivery within 24 hours and were independently associated with labor duration. Fetal fibronectin and ultrasound measurements failed to predict accurately the outcome of induced labor.

Pre-induction sonographic measurement of cervical length in prolonged pregnancy: the effect of parity in the prediction of induction-to-delivery interval

OBJECTIVE

To examine the effect of parity on the relationship between pre-induction cervical length and the induction-to-delivery interval and rate of vaginal delivery within 24 h in women undergoing induction of labor for prolonged pregnancy.

METHODS

In 382 singleton pregnancies, induction of labor was carried out at 41 + 3 to 42 + 1 weeks of gestation. The cervical length was measured by transvaginal sonography before induction. Univariate analyses were performed by constructing Kaplan-Meier survival curves for the induction-to-delivery interval for various subgroups, and comparing these using log rank tests. Multivariate analyses were performed using the Cox proportional hazards model and multiple linear regression.

RESULTS

Successful vaginal delivery within 24 h of induction occurred in 67% of the women and the pre-induction cervical length was significantly associated with the induction-to-delivery interval and the rate of vaginal delivery within 24 h. Sonographically measured cervical length was better than the Bishop score or cervical length by vaginal examination in predicting the outcome of induction. Parity provided a significant independent contribution, in addition to pre-induction cervical length, in the prediction of the outcome of labor. Thus, in multiparae the incidence of successful vaginal delivery within 24 h of induction was about 30% higher than in nulliparae. For the same cervical length, the induction-to-delivery interval in multiparae was 37% lower than in nulliparae.

CONCLUSION

In women undergoing induction of labor for prolonged pregnancy, cervical length and parity provide independent prediction of induction-to-delivery interval and the likelihood of vaginal delivery within 24 h of induction.