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

Recommendations for strain elastography of the uterine cervix

PURPOSE

Conventional vaginal strain ultrasound elastography, not based on shear-wave elastography imaging, can assess the biomechanical properties of the uterine cervix. This assessment may inform the risks of preterm birth and failed induction of labor. However, there is considerable variation in the approaches to strain elastography, including the placement of the region of interest (ROI). Therefore, our aim was to provide recommendations for cervical elastography.

METHODS

We conducted a literature review on (1) elastography principles, and (2) the cervical anatomy. Subsequently, we performed elastography scanning using a Voluson™ E10 Expert scanner with the BT18 software of (3) polyacrylamide hydrogel simulators, and (4) pregnant women.

RESULTS

Increasing the distance between the ROI and probe led to a decrease in the obtained strain value; a 53% decrease was observed at 17.5 mm. Similarly, an increased angle between the ROI and probe-centerline resulted in a 59% decrease for 40° angle. Interposition of soft tissue (e.g., cervical canal) between the ROI and the probe induced an artifact with values from the posterior lip being 54% lower than those from the anterior lip, even after adjusting for probe-ROI distance. Equipment and the recording conductance significantly influenced the results.

CONCLUSION

Our findings inform recommendations for future studies on strain cervical elastography.

Descent of the presenting part assessed with ultrasound

Fetal head descent can be expressed as fetal station and engagement. Station is traditionally based on clinical vaginal examination of the distal part of the fetal skull and related to the level of the ischial spines. Engagement is based on a transabdominal examination of the proximal part of the fetal head above the pelvic inlet. Clinical examinations are subjective, and objective measurements of descent are warranted. Ultrasound is a feasible diagnostic tool in labor, and fetal lie, station, position, presentation, and attitude can be examined. This review presents an overview of fetal descent examined with ultrasound. Ultrasound was first introduced for examining fetal descent in 1977. The distance from the sacral tip to the fetal skull was measured with A-mode ultrasound, but more convenient transperineal methods have since been published. Of those, progression distance, angle of progression, and head-symphysis distance are examined in the sagittal plane, using the inferior part of the symphysis pubis as reference point. Head-perineum distance is measured in the frontal plane (transverse transperineal scan) as the shortest distance from perineum to the fetal skull, representing the remaining part of the birth canal for the fetus to pass. At high stations, the fetal head is directed downward, followed with a horizontal and then an upward direction when the fetus descends in the birth canal and deflexes the head. Head descent may be assessed transabdominally with ultrasound and measured as the suprapubic descent angle. Many observational studies have shown that fetal descent assessed with ultrasound can predict labor outcome before induction of labor, as an admission test, and during the first and second stage of labor. Labor progress can also be examined longitudinally. The International Society of Ultrasound in Obstetrics and Gynecology recommends using ultrasound in women with prolonged or arrested first or second stage of labor, when malpositions or malpresentations are suspected, and before an operative vaginal delivery. One single ultrasound parameter cannot tell for sure whether an instrumental delivery is going to be successful. Information about station and position is a prerequisite, but head direction, presentation, and attitude also should be considered.

Diagnostic accuracy of pre-induction cervical elastography, volume, length, and uterocervical angle for the prediction of successful induction of labor with dinoprostone

PURPOSE

The study's aim is to define among a group of ultrasonographic cervical measurements a candidate parameter predictive of successful of induction of labor in term pregnancies with unfavorable cervix.

METHODS

This prospective observational study included 141 pregnant women at term with an unfavorable cervix (Bishop score ≤ 6). All patients underwent clinical and ultrasonographic cervical evaluation before dinoprostone induction. Pre-induction cervical assessments included the Bishop score, cervical length, cervical volume, uterocervical angle, and cervical elastographic parameters. Vaginal delivery (VD) was accepted as successful dinoprostone induction. Multivariate logistic regression was conducted to identify the potential risk factors significantly associated with CS while controlling for possible confounding variables.

RESULTS

The vaginal delivery rate was 74% (n = 93) and the cesarean section (CS) rate was 26% (n = 32). Sixteen patients who had a cesarean section due to fetal distress before the active phase of labor were excluded from the study. The mean induction-to-delivery interval was 1176.1 ± 352 (540-2150) for VD and 1359.4 ± 318.4 (780-2020) for CS (p = 0.01). Bishop score was lower in women with cesarean section (p = 0.002). When both groups were compared in terms of delivery type, no difference was found between cervical elastography values, cervical volume, cervical length, and uterocervical angle measurements. Multivariable logistic regression model failed to show significant differences between cervical elastography values, cervical volume, cervical length, and uterocervical angle measurements.

CONCLUSION

Cervical length, cervical elastography, cervical volume, and uterocervical angle measurements did not provide a clinically useful prediction of outcomes following labor induction in our study group with unfavorable cervix. Cervical length measurements significantly predicted the time interval from induction to delivery.

A predictive model for successfully inducing active labor among pregnant women: Combining cervical status assessment and clinical characteristics

Objective

To develop a predictive model for successfully inducing active labor by using a combination of cervical status and maternal and fetal characteristics.

Study design

A retrospective cohort study was conducted among pregnant women who underwent labor induction between January 2015 and December 2019. Successfully inducing active labor was defined as achieving a cervical dilation > 4 cm within 10 h after adequate uterine contractions. The medical data were extracted from the hospital database; statistical analyses were performed using a logistic regression model to identify the predictors associated with the successful induction of labor. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to assess the accuracy of the model.

Results

In total, 1448 pregnant women were enrolled; 960 (66.3 %) achieved successful induction of active labor. Multivariate analysis revealed that maternal age, parity, body mass index, oligohydramnios, premature rupture of membranes, fetal sex, dilation, station, and consistency were significant factors associated with successful labor induction. The ROC curve of the logistic regression model had an AUC of 0.7736. For the validated score system to predict the probability of success, we found that a total score > 60 has a 73.0 % (95 % CI 59.0-83.5) probability of successful induction of labor into the active phase stage within 10 h.

Conclusions

The predictive model for successfully achieving active labor using the combination of cervical status and maternal and fetal characteristics had good predictive ability.

Predictive Value of Cervical Shear Wave Elastography in the Induction of Labor in Late-Term Pregnancy Nulliparous Women: Preliminary Results

The prediction of induction of labor continues to be a paradigm nowadays. Bishop Score is the traditional widely spread method but with a low reliability. Ultrasound cervical assessment has been proposed as an instrument of measurement. Shear wave elastography (SWE) should be a promising tool in the prediction of the success of labor induction in nulliparous late-term pregnancies. Ninety-two women with nulliparous late-term pregnancies who were going to be induced were included in the study. A shear wave measurement of the cervix divided into six regions (inner, middle and outer in both cervical lips), cervical length and fetal biometry was performed by blinded investigators prior to routine hand cervical assessment (Bishop Score (BS)) and induction of labor. The primary outcome was success of induction. Sixty-three women achieved labor. Nine women did not, and they underwent a cesarean section due to failure to induce labor. SWE was significantly higher in the inner part of the posterior cervix (p < 0.0001). SWE showed an area under the curve (AUC): 0.809 (0.677-0.941) in the inner posterior part. For CL, AUC was 0.816 (0.692-0.984). BS AUC was 0.467 (0.283-0.651). The ICC of inter-observer reproducibility was ≥0.83 in each region of interest (ROI). The cervix elastic gradient seems to be confirmed. The inner part of the posterior cervical lip is the most reliable region to predict induction of labor results in SWE terms. In addition, cervical length seems to be one of the most important procedures in the prediction of induction. Both methods combined could replace the Bishop Score.

Propess versus prostin for induction of labour in term primiparous women

BACKGROUND

The rate of induction of labour has increased over the decades and numerous medications are available in the market. This study compares the efficacy and safety between dinoprostone slow-release pessary (Propess) and dinoprostone tablet (Prostin) for labour induction at term in nulliparous women.

METHODS

This was a prospective single-blind randomized controlled trial conducted in a tertiary medical centre in Taiwan from September 1, 2020 to February 28, 2021. We recruited nulliparous women at term with a singleton pregnancy, fetus in cephalic presentation, an unfavourable cervix, and the cervical length had been measured by transvaginal sonography three times during labour induction. The main outcomes are duration from induction of labour to vaginal delivery, vaginal delivery rate, maternal and neonatal complication rates.

RESULTS

In both groups, Prostin and Propess, 30 pregnant women were enrolled. The Propess group had higher vaginal delivery rate but it did not meet statistically significant difference. The Prostin group had significantly higher rate of adding oxytocin for augmentation (p = 0.0002). No significant difference was observed in either labouring course, maternal or neonatal outcomes. The probability of vaginal delivery was independently related to the cervical length measured by transvaginal sonography 8 h after Prostin or Propess administration as well as neonatal birth weight.

CONCLUSION

Both Prostin and Propess can be used as cervical ripening agents with similar efficacy and without significant morbidity. Propess administration was associated with higher vaginal delivery rate and less need to add oxytocin. Intrapartum measurement of cervical length is helpful in predicting successful vaginal delivery.

Quantitative sonoelastography of the uterine cervix in predicting successful outcome of induction of labour

Objectives

The aim of the study was to evaluate the stiffness of cervix and determine its significance in predicting successful outcome of induction of labour. The primary objective was to determine the differences in elastography indices of different areas of cervix between the outcome groups of successful and failed induction of labour. A secondary objective was to find out the correlation of these elastography indices with Bishop's score and cervical length.

Methods

This was a prospective, observational study conducted over a period of 6 months on pregnant women admitted in the labour room for induction of labour. Establishment of adequate regular uterine contractions - at least three contractions lasting 40-45 s in a 10-min period - was taken as end point for successful outcome of induction of labour. Even after 24 h of initiation of induction of labour, regular, adequate and painful uterine contractions were not established, then induction of labour was described as having failed. Prior to induction, cervical length measurement, Bishop's scoring and elastographic evaluation of the cervix were done by stress-strain elastography. A colour map was produced from purple to red and a five-step scale - the elastography index - was used to describe the various parts of the cervix. The differences between elastography indices of different parts of cervix were estimated using Mann-Whitney U test. Correlation of the indices with cervical length and Bishop's score was determined by Spearman's correlation coefficient.

Results

A total of 64 women were included in the study. A significant difference (p < 0.001) was found in the elastography index of internal os between the two outcome groups of success (1.76 ± 0.64) and failure (0.54 ± 0.18). However, the elastography index of central cervical canal, external os, anterior lip and posterior lips did not differ significantly across the outcome groups. A significant positive correlation was found between elastography index of internal os and cervical length (Spearman's correlation coefficient, r = 0.441, p < 0.001) and between elastography index of external os and cervical length (r = 0.347, p = 0.005), whereas a negative correlation was seen between elastography index of external os and Bishop's score (r = -0.270, p = 0.031).

Conclusion

Elastography index of internal os can be used to predict outcome of induction of labour. Cervical elastography is a promising new technique for cervical consistency assessment. Further larger studies are required to determine some cut-off point for elastography index of internal os in prediction of outcome of induction of labour and to strongly establish the usefulness of cervical elastography for pregnancy management, preventing preterm delivery and establishment of cut-off points to determine successful induction.

Association between the cervical sliding sign and successful induction of labor in women with an unfavorable cervix: A prospective observational study

OBJECTIVES

To evaluate the role of the cervical sliding sign (CSS) in the prediction of the outcome of induction of labor (IOL).

STUDY DESIGN

Two-center prospective observational cohort study involving a non-consecutive series of uncomplicated singleton term pregnancies, planned for IOL, with a fetus in cephalic presentation and unfavorable cervix as defined by a Bishop score ≤ 6. The Bishop score was evaluated by transvaginal digital examination and the cervical length and CSS by transvaginal ultrasound. The presence of CSS was defined as the sliding of the anterior cervical lip on the posterior one under gentle pressure of the transvaginal probe. The primary outcome of the study was successful vaginal delivery within 24 h. The secondary outcome was the induction-to-active-labor time. The interobserver agreement for the CSS was also evaluated.

RESULTS

Over a period of 12 months, 179 women were included. The CSS was found in 86 (48.0 %) patients and was associated with an increased likelihood of vaginal delivery within 24 h (60/86 or 69.8 % vs 27/93 or 29.0 %, P < 0.001) and a shorter induction-to-active-labor time (954 ± 618 min vs 1416 ± 660 min, P < 0.001). Multivariable regression analysis showed that the CSS was an independent predictor of vaginal delivery within 24 h (aOR 5.37, 95 % CI 2.26-12.75) and shorter induction-to-active-labor time interval (HR 1.81, 95 % CI 1.19-2.74). The interobserver variability based on intraclass correlation coefficient for the CSS was excellent (ICC = 0.90).

CONCLUSION

In women undergoing IOL with an unfavorable cervix, the CSS is associated with a higher frequency of vaginal delivery within 24 h and a shorter induction-to-active-labor time.

The correlation between levator ani co-activation and fetal head regression on maternal pushing at term

OBJECTIVE

To assess the correlation between fetal head regression and levator ani muscle (LAM) co-activation under Valsalva maneuver.

STUDY DESIGN

This study was a secondary analysis of a prospective cohort study on the association between the angle of progression (AoP) and labor outcome. We scanned a group of nulliparous women at term before the onset of labor at rest and under maximum Valsalva maneuver. In addition to the previously calculated AoP, in the present study, we measured the anteroposterior diameter of LAM hiatus (APD) on each ultrasound image. LAM co-activation was defined as APD at Valsalva less than that at rest, whereas fetal head regression was defined as AoP at Valsalva less than that at rest. We calculated the correlation between the two phenomena. Finally, we examined various labor outcomes according to the presence, absence, or co-existence of these two phenomena.

RESULTS

We included 469 women. A total of 129 (27.5%) women presented LAM co-activation while 50 (10.7%) showed head regression. Only 15 (3.2%) women showed simultaneous head regression and LAM co-activation. Women with coexisting LAM co-activation and head regression had the narrowest AoP at Valsalva in comparison with other study groups (p < .001). In addition, they had the highest risk of Cesarean delivery (40%) and longest first, second, and active second stage durations, although none of these reached statistical significance.

CONCLUSION

In nulliparous women at term before the onset of labor fetal head regression and LAM co-activation at Valsalva are two distinct phenomena that uncommonly coexist.

Nomogram Incorporating Multimodal Transvaginal Ultrasound Assessment at 20 to 24 Weeks' Gestation for Predicting Spontaneous Preterm Delivery in Low-Risk Women

Background

The majority of women who experience spontaneous preterm delivery (SPTD) have low-risk, asymptomatic pregnancies with a cervical length (CL) ≥25mm and no clear risk factors. Despite the fact that cervical elastography is a potential tool for predicting SPTD, there is currently no feasible solution to make a reliable prediction for preventing SPTD.

Objective

The aim of this study was to construct a nomogram including multimodal transvaginal ultrasound parameters during the second trimester to predict SPTD in low-risk women.

Methods

This multi-center study enrolled 1260 women with singleton pregnancies between 20 and 24 weeks’ gestation. CL and cervical elastography data were obtained when they were undergoing the second-trimester anomaly scan. Univariate and multivariate Logistic regression were utilized to screen predictors independently related to SPTD from the maternal characteristics and multimodal ultrasound data. Then construct a nomogram to determine the likelihood of SPTD in pregnant women.

Results

A total of 66 pregnancies in the training cohort (7.8%, 66/842) and 37 pregnancies (8.9%, 37/418) in the validation cohort ended in SPTD. Age, uterine curettage, CL, and strain in the anterior lip of internal os were the independent predictors of SPTD (P < 0.001, < 0.001, = 0.007, and < 0.001, respectively). These predictors constituted a nomogram to predict the probability of SPTD for a pregnant woman in her second trimester. It showed good discrimination (C-index = 0.898 and 0.839), calibration (P = 0.258 and 0.115), and yielded net benefits both in the training and validation cohorts.

Conclusion

The nomogram including data of multimodal transvaginal ultrasound at 20 to 24 weeks’ gestation is expected to identify women with SPTD in the low-risk, asymptomatic population.

Labour induction in twin pregnancies

Medically-indicated deliveries are common in twin pregnancies given the increased risk of various obstetric complications in twin compared to singleton pregnancies, mainly hypertensive disorders of pregnancy and foetal growth restriction. Due to the unique characteristics of twin pregnancies, the success rates and safety of labour induction may be different than in singleton pregnancies. However, while there are abundant data regarding induction of labour in singleton pregnancies, the efficacy and safety of labour induction in twin pregnancies have been far less studied. In the current manuscript we summarize available data on various aspects of labour induction in twin pregnancies including incidence, success rate, prognostic factors, safety and methods for labour induction in twins. This information may assist healthcare providers in counselling patients with twin pregnancies when labour induction is indicated.

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.

Fetal head progression and regression on maternal pushing at term and labor outcome

OBJECTIVES

The aim of our study was two-fold. First, to evaluate the association between the change in the angle of progression (AoP) on maternal pushing and labor outcome. Second, to assess the incidence and clinical significance of the reduction of AoP on maternal pushing.

METHODS

This was a prospective cohort study of nulliparous women with singleton pregnancy at term. AoP was measured at rest and on maximum Valsalva maneuver before the onset of labor, and the difference between AoP on maximum Valsalva and that at rest (ΔAoP) was calculated for each woman. Following delivery and data collection, we assessed the association between ΔAoP and various labor outcomes, including Cesarean section (CS), duration of the first, second and active second stages of labor, Apgar score and admission to the neonatal intensive care unit (NICU). The prevalence of women with reduction of AoP on maximum Valsalva maneuver (AoP-regression group) was calculated and its association with the mode of delivery and duration of different stages of labor was assessed.

RESULTS

Overall, 469 women were included in the analysis. Among these, 273 (58.2%) had spontaneous vaginal birth, 65 (13.9%) had instrumental delivery and 131 (27.9%) underwent CS. Women in the CS group were older, had narrower AoP at rest and on maximum Valsalva, higher rate of epidural administration and lower 1-min and 5-min Apgar scores in comparison with the vaginal-delivery group. ΔAoP was comparable between the two groups. On Pearson's correlation analysis, AoP at rest and on maximum Valsalva maneuver had a significant negative correlation with the duration of the first stage of labor. ΔAoP showed a significant negative correlation with the duration of the active second stage of labor (Pearson's r, -0.125; P = 0.02). Cox regression model analysis showed that ΔAoP was associated independently with the duration of the active second stage (hazard ratio, 1.014 (95% CI, 1.003-1.025); P = 0.012) after adjusting for maternal age and body mass index. AoP reduction on maximum Valsalva was found in 73 (15.6%) women. In comparison with women who showed no change or an increase in AoP on maximum Valsalva, the AoP-regression group did not demonstrate significant difference in maternal characteristics, mode of delivery, rate of epidural analgesia, duration of the different stages of labor or rate of NICU admission.

CONCLUSIONS

In nulliparous women at term before the onset of labor, narrower AoP at rest and on maximum Valsalva, reflecting fetal head engagement, is associated with a higher risk of Cesarean delivery. The increase in AoP from rest to Valsalva, reflecting more efficient maternal pushing, is associated with a shorter active second stage of labor. Fetal head regression on maternal pushing is present in about 16% of women and does not appear to have clinical significance. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

The usefulness of ultrasound before induction of labor

The indications for induction of labor have been consistently on the rise. These indications are mainly medical (maternal or fetal) or social or related to convenience or maternal preferences. With the increase in the prevalence of these indications, the incidence rates of induction of labor are expected to rise continuously. This poses a substantial workload and financial burden on maternity healthcare systems. Failure rates of induction of labor are relatively high, especially when considering the maternal, fetal, and neonatal risks associated with emergency cesarean deliveries in cases of failure. Therefore, it is essential for obstetricians to carefully select women who are eligible for induction of labor, particularly those with no clinical contraindication and who have a reasonable chance of ending up with a successful noncomplicated vaginal delivery. Ultrasound has an established role in the various areas of obstetrical care. It is available, accessible, easy to perform, and acceptable to the patient. In addition, the learning curve for skillful obstetrical ultrasound scanning is rather easy to fulfill. Ultrasound has always had an important role in the assessment of maternal and fetal well-being. Indeed, it has been extensively explored as a reliable, reproducible, and objective tool in the management of labor. In this review, we aimed to provide a comprehensive update on the different applications and uses of ultrasound before induction of labor for the prediction of its success and the potential improvement of its health-related maternal and fetal outcomes.

Predicting cesarean delivery for failure to progress as an outcome of labor induction in term singleton pregnancy

BACKGROUND

Induction of labor is one of the most common interventions in modern obstetrics, and its frequency is expected to continue to increase. There is inconsistency as to how failed induction of labor is defined; however, the majority of studies define success as the achievement of vaginal delivery. Induction of labor in nulliparous women poses an additional challenge with a 15% to 20% incidence of failure, ending in emergency operative deliveries. The Bishop score has been traditionally used before decisions for induction of labor. Nonetheless, it is subjective and prone to marked interobserver variation. Several studies have been conducted to find alternative predictors, yet a reliable, objective method still remains to be introduced and validated. Hence, there is still a need for the development of new predictive tools to facilitate informed decision making, optimization of resources, and minimization of potential risks of failure. Furthermore, a peripartum transperineal ultrasound scan has been proven to provide objective, noninvasive assessment of labor.

OBJECTIVE

This study aimed to assess the feasibility of developing and validating an objective and reproducible model for the prediction of cesarean delivery for failure to progress as an outcome of labor induction in term singleton pregnancies.

STUDY DESIGN

This was a prospective observational cohort study conducted in Cairo University Hospitals and University of Bologna Hospitals between November 2018 and November 2019. We recruited 382 primigravidae with singleton term pregnancies in cephalic presentation. All patients had baseline Bishop scoring together with various transabdominal and transperineal ultrasound assessments of the fetus, maternal cervix, and pelvic floor. The managing obstetricians were blinded to the ultrasound scan findings. The method and indication of induction of labor, the total duration of stages of labor, mode of birth, and neonatal outcomes were all recorded. Women who had operative delivery for fetal distress or indications other than failure to progress in labor were excluded from the final analysis, leaving a total of 344 participants who were randomly divided into 243 and 101 pregnancies that constituted the model development and cross-validation groups, respectively.

RESULTS

It was possible to perform transabdominal and transperineal scans and assess all the required parameters on all study participants. Univariate and multivariate analyses were used for selection of potential predictors and model fitting. The independent predictive variables for cesarean delivery included maternal age (odds ratio, 1.12; P=.003), cervical length (odds ratio, 1.08; P=.04), angle of progression at rest (odds ratio, 0.9; P=.001), and occiput posterior position (odds ratio, 5.7; P=.006). We tested the performance of the prediction model on our cross-validation group. The calculated areas under the curve for the ability of the model to predict cesarean delivery were 0.7969 (95% confidence interval, 0.71-0.87) and 0.88 (95% confidence interval, 0.79-0.97) for the developed and validated models, respectively.

CONCLUSION

Maternal age and sonographic fetal occiput position, angle of progression at rest, and cervical length before labor induction are very good predictors of induction outcome in nulliparous women at term.

Predictive value of cervical length by ultrasound and cervical strain elastography in labor induction at term

OBJECTIVE

This study aimed to examine whether addition of cervical elastographic parameters measured by ElastoScan for the cervix (E-cervix) improves the predictive value of cervical length (CL) in induction of labor at term by dinoprostone.

METHODS

We conducted a prospective, observational study between January 2020 and June 2020 in term primiparous women (n = 73) who were scheduled for labor induction by a 10-mg dinoprostone vaginal insert. The time intervals from the start of labor induction to regular uterine contractions and to vaginal delivery were calculated as the primary outcomes. We divided subjects into two groups using a threshold of 24 hours. Ultrasound measurements were compared between the two groups and the area under the curve (AUC) of the prediction model was calculated.

RESULTS

Women who delivered vaginally within 24 hours had a shorter CL and softer cervix than those who delivered after 24 hours. The combination of CL and elastographic parameters increased the AUC to 0.672 compared with CL alone (AUC = 0.637).

CONCLUSIONS

Measurement by E-cervix is relatively reproducible. Addition of cervical strain elastography slightly improves the predictive performance of CL in vaginal delivery within 24 hours. This technique is a promising ancillary tool for use with ultrasound.

The degree of cervical length shortening as a predictor of successful or failed labor induction

OBJECTIVE

To evaluate whether the degree of cervical length change was associated with successful cervical dilatation during labor induction.

MATERIALS AND METHODS

We conducted a secondary analysis of a prospective observational study of term singleton pregnant women who underwent labor inductions. Cases of Cesarean section due to fetal distress or maternal request during the first stage of labor were excluded. The enrolled women were categorized into two groups according to achievement of full cervical dilatation. The cervical length near induction and cervical length shortening over the last four weeks of pregnancy were compared between the two groups. A receiver operating characteristics (ROC) analysis was performed to evaluate the screening performance for failed cervical dilatation during labor induction.

RESULTS

A total of 165 women were enrolled for the final analysis; of these, 145 (87.9%) women reached the second stage of labor and 20 (12.1%) women failed to achieve full cervical dilatation. Women who failed to achieve full cervical dilatation had a significantly longer cervical length near induction and less cervical length change over previous four weeks compared with women who achieved full cervical dilatation (P = 0.018 and 0.005, respectively). Multivariate analysis showed that cervical length >29 mm (odds ratios [OR], 4.15; 95% confidence interval [CI], 1.290-13.374, P = 0.017) and cervical length shortening ≦ 6 mm (OR, 5.87; 95% CI, 1.552-22.271, P = 0.009) were significantly associated with failed cervical dilatation after adjusting for birthweight and previous history of vaginal delivery. Cervical length shortening alone provided a better prediction of failed cervical dilatation than the combination of cervical length and shortening (sensitivity, 76.9%; specificity, 63.8%).

CONCLUSION

The probability of failed cervical dilatation during labor induction was significantly increased in cases when the cervical length was greater than 29 mm near induction or when the cervical length shortening was less than 6 mm over the last four weeks.

Ultrasound assessment of the cervix in predicting successful membrane sweeping: a prospective observational study

OBJECTIVE

Membrane sweeping has been shown to potentially reduce the need for formal induction of labor. The primary aim of this study was to elucidate the role of ultrasound assessment of the cervix in predicting successful membrane sweeping in singleton pregnancies at term; the secondary aim was to build a multiparametric prediction model integrating, maternal, pregnancy and ultrasound characteristics, able to anticipate spontaneous delivery at term.

METHODS

Prospective observational study including singleton pregnancies at term undergoing membrane sweeping. Cervical length (CL) and posterior cervical angle (PCA) were assessed on ultrasound immediately before the procedure. Primary outcome was successful membrane sweeping, defined as spontaneous vaginal birth without formal induction within the 24hours. A subgroup analysis was computed considering women experiencing spontaneous vaginal birth within 48 hours from the procedure. The secondary outcome was to explore the diagnostic performance of a multiparametric model including maternal, pregnancy, and ultrasound assessment of the cervix in predicting spontaneous vaginal birth following membrane sweeping. Multivariate logistic regression and area under the curve (ROC) analyses were used to compute the data.

RESULTS

One hundred fifty-nine singleton pregnancies undergoing membrane sweeping were included in the analysis. Successful membrane sweeping within 24 hours occurred in 68/159 women (36.5%). Parity (aOR = 1.87, 95% confidence interval [CI] 1.2-2.44), gestational age (aOR = 1.32, 95% CI 1.14-1.76), CL (aOR = 0.47, 95%CI 0.31-0.69) and PCA (aOR = 1.22, 95%CI 1.07-1.41) were independently associated with spontaneous vaginal birth within 24 hours from sweeping. The AUC of the constructed model was 0.796 (95% CI 0.727-0.865). Likewise, CL (aOR = 0.80, 95%CI 0.72-0.89), PCA (aOR = 1.19, 95%CI 1.10-1.28) and gestational age at the procedure (aOR = 1.65, 95%CI 1.09-1.86; p = .04) were independently associated with delivery within 48 hours with an AUC of 0.737 (95%CI 0.659-0.815).

CONCLUSIONS

Cervical ultrasound assessment of the cervix prior to membrane sweeping is associated with spontaneous vaginal birth within 24 and 48 hours from the procedure. The combination of cervical ultrasonographic parameters with parity and gestational age can predict the chances of delivery within 24 or 48 hours from membrane sweeping. The findings from this study support the use of ultrasound assessment of the cervix prior to membrane sweeping in order to more accurately predict the likelihood of spontaneous vaginal delivery.

Cervical elastography strain ratio and strain pattern for the prediction of a successful induction of labour

OBJECTIVES

The aim of this study was to introduce cervical strain elastography to objectively assess the cervical tissue transformation process during induction of labour (IOL) and to evaluate the potential of cervical elastography as a predictor of successful IOL.

METHODS

A total of 41 patients with full-term pregnancies elected for an IOL were included. Vaginal ultrasound with measurement of cervical length and elastography and assessment of the Bishop Score were performed before and 3 h after IOL. The measured parameters were correlated to the outcome of IOL and the time until delivery.

RESULTS

We observed an association between the strain pattern and the value of the strain ratio 3 h after IOL and a successful IOL (p=0.0343 and p=0.0342, respectively) which can be well demonstrated by the results after 48 h. In our study population the cervical length and the Bishop Score did not prove to be relevant parameters for the prediction of a successful IOL.

CONCLUSIONS

We demonstrated for the first time that the cervical elastography pattern after the first prostaglandine application can help predict the outcome of IOL.

Viscoelastic model characterization of human cervical tissue by torsional waves

The understanding of changes in the viscoelastic properties of cervical tissue during the gestation process is a challenging problem. In this work, we explore the importance of considering the multilayer nature (epithelial and connective layers) of human cervical tissue for characterizing the viscoelastic parameters from torsional waves. For this purpose, torsional wave propagations are simulated in three multilayer cervical tissue models (pure elastic, Kelvin-Voigt (KV) and Maxwell) using the finite difference time domain method. High-speed camera measurements have been carried out in tissue-mimicking phantoms in order to obtain the boundary conditions of the numerical simulations. Finally, a parametric modeling study through a probabilistic inverse procedure was performed to rank the most plausible rheological model and to reconstruct the viscoelastic parameters. The procedure consist in comparing the experimental signals obtained in human cervical tissues using the Torsional Wave Elastography (TWE) technique with the synthetic signals from the numerical models. It is shown that the rheological model that best describes the nature of cervical tissue is the Kelvin-Voigt model. Once the most plausible model has been selected, the stiffness and viscosity parameters have been reconstructed of the epithelial and connective layers for the measurements of the 18 pregnant women, along with the thickness of the epithelial layer.

Temperature Elevation in an Instrumented Phantom Insonated by B-Mode Imaging, Pulse Doppler and Shear Wave Elastography

Diagnostic ultrasound is the gold standard for obstetric scanning and one of the most important imaging techniques for perinatal and neonatal monitoring and diagnosis. Ultrasound provides detailed real-time anatomic information, including blood flow measurements and tissue elasticity. The latter is provided through various techniques including shear wave elastography (SWE). SWE is increasingly used in many areas of medicine, especially in detection and diagnosis of breast, thyroid and prostate cancers and liver disease. More recently, SWE has found application in gynaecology and obstetrics. This method mimics manual palpation, revealing the elastic properties of soft biological tissues. Despite its rising potential and expanding clinical interest in its use in obstetrics and gynaecology (such as for assessment of cervical ripening or organ development and structure during pregnancy), its effects on and potential risks to the developing fetus remain unknown. Risks should be evaluated by regulatory bodies before recommendations are made on the use of SWE. Because ultrasound is known to produce thermal and mechanical effects, this study measured the temperature increase caused by B-mode, pulse Doppler (PD) and SWE, using an instrumented phantom with 11 embedded thermocouples. Experiments were performed with an Aixplorer diagnostic ultrasound system (Supersonic Imagine, Aix-en-Provence, France). As expected, the greatest heating was detected by the thermocouple closest to the surface in contact with the transducer (2.9°C for SWE, 1.2°C for PD, 0.7°C for B-mode after 380-s excitation). Both conduction from the transducer face and direct heating owing to ultrasound waves contribute to temperature increase in the phantom with SWE associated with a larger temperature increase than PD and B-mode. This article offers a methodological approach and reference data for future safety studies, as well as initial recommendations about SWE safety in obstetrics and gynaecology.

A Preliminary Study on the Safety of Elastography during Pregnancy: Hypoacusia, Anthropometry, and Apgar Score in Newborns

Transient or acoustic radiation force elastography (ARFE) is becoming the most extended technology to assess cervical effacement, additionally to the Bishop test and conventional ultrasound. However, a debate on the fetal safety has been opened due to the high intensity focused beam emitted to produce shear waves. This work is aimed at providing preliminary data to assess clinical effects of fetal exposure. A follow-up study in newborns of 42 women exposed to ARFE during pregnancy was carried out to explore neonatal hypoacusia, Apgar test, and anthropometry. No hypoacusia cases attributable to ARFE were observed. The Apgar test at five minutes scored normally in all the newborns. Comparisons between anthropometric measurements showed no significant statistically differences. The results preclude to state the harmfulness nor the safety of ARFE. However, given the concern on the high level of energy and the potential risk of harmful bioeffects, larger studies are recommended.

USEFULNESS OF TRANSPERINEAL VIRTUAL TOUCH QUANTIFICATION IN THE CERVIX FOR PREDICTING OUTCOME OF LABOR INDUCTION

This study aimed to explore the feasibility of transperineal virtual touch tissue quantification (VTQ) for predicting the outcome of labor induction. A total of 80 nulliparous pregnant women were included. Before labor induction, cervical length was measured by B-mode sonography, cervical stiffness was measured by VTQ, and Bishop score was assessed by vaginal examination. Subsequently, labor was induced using standard oxytocin infusion in all patients. Delivery within 24 hours after labor induction was classified as spontaneous delivery; otherwise, cesarean delivery was performed. Out of 80 participants, 48 (60%) delivered vaginally and 32 (40%) underwent cesarean delivery. The cervical length was significantly longer and the shear wave velocity (SWV) was greater in the cesarean delivery group than in the vaginal delivery group (p = 0.004 and p < 0.000, respectively). Logistic regression analysis indicated that only the mean SWV had independent predictive value for the outcome of labor induction (p = 0.011). The best diagnostic cut-off point of the mean SWV was 1.23 m/s, with a sensitivity of 93.8% and a specificity of 89.6%. Transperineal VTQ technique could predict the outcome of labor induction using oxytocin.

Feasibility, Reliability, and Agreement of Transperineal Ultrasound Measurement: Results from a Longitudinal Cohort Study

OBJECTIVES

To evaluate the feasibility, reliability, and agreement of serial transperineal ultrasound (TPU) assessment of fetal head station (parasagittal angle of progression [psAOP], head-perineum distance [HPD], and head-symphysis distance [HSD]) and sonographic cervical dilatation (SCD), compared to fetal head station and cervical dilatation determined by vaginal examination, respectively.

METHODS

This was a prospective longitudinal study in singleton pregnancies undergoing induction of labor at term. Paired assessment of fetal head station and cervical dilatation by vaginal examination, with TPU assessment of psAOP, HPD, HSD, and SCD was made serially. Feasibility, correlation, reliability, and agreement were determined.

RESULTS

1,139 paired measurements among 326 women were included. psAOP and HPD were achievable in all assessments. HSD was not achievable in 3.4% (11/326) due to high fetal head station. Fetal head station by vaginal examination was positively correlated with psAOP (rho = 0.70) but negatively correlated with HPD (rho = -0.57) and HSD (rho = -0.52). The feasibility to measure SCD reduced as cervical dilatation increased. Cervical dilatation and SCD were positively correlated (rho = 0.96) with strong agreement (concordant correlation coefficient = 0.925).

CONCLUSIONS

Measurements of psAOP and HPD are feasible and correlate significantly with fetal head station by vaginal examination. Measurement of HSD is not feasible when fetal head station is high. Measurement of SCD is feasible, but it is more difficult in the advanced stage of labor. The correlation, reliability, and agreement between SCD and cervical dilatation by vaginal examination are high.

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.

ACR Appropriateness Criteria® Assessment of Gravid Cervix

Preterm birth remains the leading cause of perinatal morbidity and mortality. Although the greatest risk factor for preterm birth is a history of prior preterm birth, a short cervical length (≤25 mm) before 24 weeks' gestational age is also associated with increased risk of spontaneous preterm delivery. As such, cervical length assessment has become of particular interest in predicting those patients at risk for preterm birth. Other clinical scenarios (eg, preterm labor, induction of labor, and active labor) may arise, in which assessment of the cervix may be of interest. Ultrasound is the mainstay imaging modality for assessing the gravid cervix, with transvaginal ultrasound recommended in patients at high risk for preterm birth or suspected preterm labor. Transperineal ultrasound is an alternate approach in those cases where transvaginal ultrasound in contraindicated. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Evaluation of Cervical Elastography for Prediction of Spontaneous Preterm Birth in Low-Risk Women: A Prospective Study

OBJECTIVES

The aim of this study was to determine whether cervical elastographic parameters in addition to cervical length (CL) during the 3 trimesters of pregnancy would be predictive of spontaneous preterm birth (sPTB) among low-risk women.

METHODS

This work was a prospective nested case-control study evaluating cervical elastographic parameters and CL in low-risk women during the 3 trimesters of pregnancy. A binary logistic regression analysis was used to calculate significant covariates for prediction of sPTB. The area under the curve of the prediction model was calculated by using a receiver operating characteristic curve.

RESULTS

There were 286 women (26 cases and 260 controls) included in the analysis. The parameters of cervical elasticity became softened and heterogeneous during the 3 trimesters of pregnancy in both women with and without sPTB. The differences in the mean strain value at the internal os of the cervix (IOS), ratio (strain ratio of the internal os to the external os) during the second trimester and the IOS during the third trimester between the groups had statistical significance (P < .01; P = .01; P < .01, respectively). The CL had no association with sPTB during the 3 trimesters. The IOS during the second trimester was a better predictor of sPTB, with an area under the curve of 0.730, and sensitivity was 72.73%.

CONCLUSIONS

We observed multiple elastographic parameters and demonstrated the physiologic changes in the cervix during the 3 trimesters of pregnancy. Furthermore, we found that the IOS during the second trimester can be helpful in predicting sPTB. However, the CL had no association with sPTB during the 3 trimesters of pregnancy.

Quantitative elastography of cervical stiffness during the three trimesters of pregnancy with a semiautomatic measurement program: A longitudinal prospective pilot study

AIM

To assess the reproducibility of a semiautomatic quantification tool for cervical stiffness and evaluate the normal changes in cervical elasticity during the three trimesters of pregnancy.

METHODS

This longitudinal prospective pilot study evaluated cervical elasticity during the three trimesters of pregnancy (11-14, 20-24 and 28-32 weeks) in women with singleton pregnancies. Women with a history of conization, cerclage, cervical Naboth cysts (diameter > 10 mm), cervical tumors, or uterine malformation were excluded. A semiautomatic tool was used to evaluate the stiffness of the whole cervix and the internal and external cervical os with multiple quantitative elasticity parameters and the cervical length (CL) on the sagittal view via transvaginal elastography. Intraclass correlation coefficients (ICC) and Bland-Altman analysis were used to assess intra- and interobserver variability. E-Cervix parameters during the three trimesters were compared using the Friedman test.

RESULTS

In total, 217 women with 651 strain examinations during the three trimesters were included. The intra- and interobserver ICC for the E-Cervix parameters ranged from 0.947 to 0.991 and 0.855 to 0.989, respectively. There were significant differences in all parameters among the three trimesters. Cervical elasticity showed significant softening and became heterogeneous during the three trimesters. The median CL was significantly shorter in the first trimester than in the second and third trimesters (P = 0.004, P < 0.001).

CONCLUSION

E-Cervix provides a graphical tool for operators to easily define regions of interest and obtain multiple repeatable measures of elasticity. The normal references for E-Cervix parameters during the three trimesters reflect the physiological cervical changes during pregnancy.

The predictive value of cervical shear wave elastography in the outcome of labor induction

Introduction

Bishop score, the traditional method to assess cervical condition, is not a promising predictive tool of the outcome of labor induction. As an objective assessment tool, many cervical ultrasound measurements have been proposed to represent the individual components of the Bishop score, but none of them can measure the cervical stiffness. Cervical shear wave elastography is a novel tool to assess the cervical stiffness quantitatively.

Material and methods

A total of 475 women who required labor induction were studied prospectively. Prior to routine digital assessment of the Bishop score, transvaginal sonographic measurement of cervical length, posterior cervical angle, angle of progression and shear wave elastography was performed. Shear wave elastography measurement was made at the inner, middle and outer regions of the cervix to assess homogeneity. Association of labor induction outcomes including the overall cesarean section and subgroups of cesarean section for failure to enter active phase, with cervical sonographic parameters and the Bishop score, were assessed using multivariate regression analyses. The predictive accuracy of the outcomes using models based on ultrasound measurement and the Bishop score was compared using the area under the receiver‐operating characteristics curves.

Results

Among 475 women, 82 (17.3%) required cesarean section. Shear wave elasticity was significantly higher in the inner cervical region than in other regions, indicating a greater stiffness (P < 0.001). Both inner cervical shear wave elasticity and cervical length were independent predictors of overall cesarean section (respective adjusted odds ratio [95% CI] 1.338 [1.001‐1.598] and 1.717 [1.077‐1.663]) and cesarean section for failure to enter active phase (respective adjusted odds ratio [95% CI] 1.689 [1.234‐2.311] and 2.556 [1.462‐4.467]), after adjusting for other covariates. Outcome prediction models using inner cervical shear wave elasticity and cervical length, had increased area under curve compared with models using the Bishop score (0.888 vs 0.819, P = 0.009).

Conclusions

The cervix is not a homogenous structure, with the inner cervix having the highest stiffness, which is an independent predictor of overall cesarean section, and specifically for those indicated because of failure to enter active phase. Models based on shear wave elastography and cervical length had higher predictive accuracy than models based on the Bishop score.

Recent advances in the induction of labor

The rate of labor induction is steadily increasing and, in industrialized countries, approximately one out of four pregnant women has their labor induced. Induction of labor should be considered when the benefits of prompt vaginal delivery outweigh the maternal and/or fetal risks of waiting for the spontaneous onset of labor. However, this procedure is not free of risks, which include an increase in operative vaginal or caesarean delivery and excessive uterine activity with risk of fetal heart rate abnormalities. A search for "Induction of Labor" retrieves more than 18,000 citations from 1844 to the present day. The aim of this review is to summarize the controversies concerning the indications, the methods, and the tools for evaluating the success of the procedure, with an emphasis on the scientific evidence behind each.

Labor progress determined by ultrasound is different in women requiring cesarean delivery from those who experience a vaginal delivery following induction of labor

BACKGROUND

The diagnosis of labor dystocia generally is determined by the deviation of labor progress, which is assessed by the use of a partogram. Recently, intrapartum transperineal ultrasound for the assessment of fetal head descent has been introduced to assess labor progress in the first stage of labor in a more objective and noninvasive way.

OBJECTIVE

The objective of the study was to determine the differences in labor progress by the use of serial transperineal ultrasound assessment of fetal head descent between women having vaginal and cesarean delivery.

STUDY DESIGN

This was a prospective longitudinal study performed in 315 women with singleton pregnancy who were undergoing labor induction at term between December 2016 and December 2017. Paired assessment of cervical dilation and fetal head station by vaginal examination and transperineal ultrasonographic assessment of parasagittal angle of progression and head-perineum distance were made serially after the commencement of labor induction. According to the hospital protocol, assessment was performed every 24 hours and 4 hours, respectively, during latent and active phases of labor. The researchers and the clinical team were blinded to each other's findings. The repeated measures data were analyzed by mixed effect models. To determine the effect of mode of delivery on the association between parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation, the significance of the interaction term between each mode of delivery and fetal head station or cervical dilation was determined, which accounted for parity and obesity. Area under receiver-operating characteristic curve was used to evaluate the performance of serial intrapartum sonography in predicting women with cesarean delivery because of failure to progress.

RESULTS

The total number of paired vaginal examination and ultrasound assessments was 1198, with a median of 3 per woman. The median assessment-to-assessment interval was 4.6 hours (interquartile range, 4.3-5.1 hours). Women who achieved vaginal delivery (n=261) had steeper slopes of parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation than those who achieved cesarean delivery (n=54). Objectively, an additional decrease of 5.11 and 1.37 degrees in parasagittal angle of progression was observed for an unit increase in fetal head station and cervical dilation, respectively, in women who required cesarean delivery (P<.01; P=.01), compared with women who achieved vaginal delivery, after taking account of repeated measures from individuals and confounding factors. The respective additional increases in head-perineum distance for a unit increase in fetal head station and cervical dilation were 0.27 cm (P<.01) and 0.12 cm (P<.01). A combination of maternal characteristics with the temporal changes of parasagittal angle of progression for an unit increase in fetal head station achieved an area under receiver-operating characteristic curve of 0.85 (95% confidence interval, 0.76-0.94), with sensitivity of 79% and specificity of 80%, for the prediction of women who required cesarean delivery because of failure to progress.

CONCLUSION

The differences in labor progress between vaginal and cesarean delivery have been illustrated objectively by serial intrapartum transperineal ultrasonographic assessment of fetal head descent. This tool is potentially predictive of women who will require cesarean delivery because of failure to progress.

Dynamic changes of fetal head descent at term before the onset of labor correlate with labor outcome and can be improved by ultrasound visual feedback

OBJECTIVE

The aim of the study was to evaluate the dynamic changes of angle of progression (AoP) before the onset of labor and their correlation with labor outcome and to investigate the effect of visual feedback using transperineal ultrasound on maternal pushing.

METHODS

We recruited a group of low-risk nulliparous women with singleton pregnancy at term. We measured AoP at rest, during pelvic floor contraction and Valsalva maneuver (before and after visual feedback). We compared AoP between women who delivered vaginally (VD) and those who underwent a cesarean section (CS). We also assessed the correlation between AoP and labor durations.

RESULTS

Overall, 222 women were included in the study; 129 (58.1%) had spontaneous VD, 35 (15.8%) had instrumental delivery, and 58 (26.1%) underwent CS. In comparison with rest, AoP decreased at PFMC (p < .001) and increased at first Valsalva (p < .001). AoP increased further significantly at Valsalva after visual feedback (p < .001). Women with VD had wider AoP at rest (p = .020), during Valsalva maneuver before (p = .024), and after visual feedback (p = .037). At cox regression analysis, wider AoP was associated with shorter first, second, and active second stages.

CONCLUSION

Wider AoP at rest and under Valsalva is associated with vaginal delivery, the shorter interval to delivery, and shorter labor duration in nulliparous women at term. The accuracy of AoP in the prediction of cesarean delivery is modest and is unlikely to be clinically applicable in isolation for the prediction of the mode of delivery.

In Vivo Measurement of Cervical Elasticity on Pregnant Women by Torsional Wave Technique: A Preliminary Study

A torsional wave (TW) sensor prototype was employed to quantify stiffness of the cervix in pregnant women. A cross-sectional study in a total of 18 women between 16 weeks and 35 weeks + 5 days of gestation was performed. The potential of TW technique to assess cervical ripening was evaluated by the measurement of stiffness related to gestational age and cervical length. Statistically significant correlations were found between cervical stiffness and gestational age (R2=0.370, p=0.0074, using 1 kHz waves and R2=0.445, p=0.0250, using 1.5 kHz waves). A uniform decrease in stiffness of the cervical tissue was confirmed to happen during the complete gestation. There was no significant correlation between stiffness and cervical length. A stronger association between gestational age and cervical stiffness was found compared to gestational age and cervical length correlation. As a conclusion, TW technique is a feasible approach to objectively quantify the decrease of cervical stiffness related to gestational age. Further research is required to evaluate the application of TW technique in obstetric evaluations, such as prediction of preterm delivery and labor induction failure.

Diagnostic accuracy of cervical elastography in predicting preterm delivery: A systematic review and meta-analysis

BACKGROUND

The aim of the study was to evaluate the diagnostic accuracy of cervical elastography in predicting preterm delivery (PTD).

METHODS

We searched the PubMed, EMBASE, and Cochrane databases to identify relevant studies that applied ultrasound (US) elastography to assess cervical stiffness and predict PTD. All the studies were published before December 11, 2018, and only studies published in English were collected. The cervical length (CL) was considered a comparator, and the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool was applied to assess the quality of the included studies. Summary receiver operating characteristic (SROC) modeling was performed to evaluate the diagnostic performance of cervical elastography in predicting PTD. Subgroup analyses were also performed.

RESULTS

Seven studies, including 1488 pregnant women, were included in this meta-analysis. Cervical elastography showed a summary sensitivity of 0.84 [95% confidence interval (CI): 0.68, 0.93], a specificity of 0.82 (95% CI: 0.63, 0.93), a diagnostic odds ratio of 25 (95% CI: 7, 93), and an area under the curve (AUC) of SROC of 0.90 (95% CI: 0.87-0.93). CL measurement showed that the AUC of SROC was 0.60 (95% CI: 0.56-0.64). The results of subgroup analysis showed that the summary sensitivity and specificity were different in the QUADAS-2 score subgroups.

CONCLUSION

Cervical elastography is a promising and reliable method to predict PTD. Cervical elastography showed better diagnostic performance to predict PTD than CL measurement.

Factors that affect ultrasound-determined labor progress in women undergoing induction of labor

BACKGROUND

The traditional approach to the assessment of labor progress is by digital vaginal examination; however, it is subjective and imprecise. Recent studies have investigated the role of transperineal ultrasonographic assessment of fetal head descent by measuring the angle of progression and head-perineum distance.

OBJECTIVE

The objective of this study was to evaluate factors that affected labor progress, which were defined by the transperineal ultrasonographic parameters, in women who achieved vaginal delivery.

STUDY DESIGN

This was a prospective longitudinal study performed in 315 women with singleton pregnancy who underwent labor induction at term between December 2016 and December 2017. Paired assessment of cervical dilation and fetal head station by vaginal examination and transperineal ultrasonographic assessment of fetal head descent (parasagittal angle of progression and head-perineum distance) were made serially after the commencement of labor induction until full cervical dilation. The researchers were blinded to the findings of the clinical team's vaginal examination and vice versa. The repeated measure data were analyzed by mixed effect models to identify the significant factors (age ≥35 years, obesity, parity, methods of labor induction, and epidural anesthesia) that affected the relationship between parasagittal angle of progression and head-perineum distance against fetal head station and cervical dilation.

RESULTS

The total number of paired vaginal examination and transperineal ultrasonographic assessments among the 261 women (82.9%) with vaginal delivery was 945, with a median of 3 per woman. The median assessment-to-assessment interval was 4.6 hours (interquartile range, 4.3-5.2). Multiparity and mechanical methods of labor induction were associated with a faster rate of fetal head descent, which was determined by head-perineum distance against fetal head station, than nulliparity and the use of a slow-release vaginal pessary, respectively. An additional increase of 0.10 cm in head-perineum distance was observed, for an unit increase in fetal head station in nulliparous women (P=.03) and women who had a slow-release vaginal pessary (P=.02), compared with multiparous women and those who had mechanical methods for labor induction. The use of epidural anesthesia was associated with a slower rate of fetal head descent, which was determined by both parasagittal angle of progression and head-perineum distance, against fetal head station. An additional decrease of 3.66 degrees in parasagittal angle of progression (P=.04) and an additional increase in 0.33 cm in head-perineum distance (P≤.001) were observed for a unit increase in fetal head station in women with the use of epidural anesthesia, compared with those without. Obese women had higher head-perineum distance overall, compared with normal weight women; at different cross-sections of time periods, obesity appeared to be associated with a slower rate of change between head-perineum distance and cervical dilation. Advanced maternal age did not affect transperineal ultrasound-determined labor progress (P>.05).

CONCLUSION

Parity, methods of labor induction, the use of epidural anesthesia, and obesity affect labor progress, which has been illustrated objectively by serial transperineal ultrasonographic assessment of fetal head descent.

Cervical consistency index and risk of Cesarean delivery after induction of labor at term

OBJECTIVE

To evaluate the association between the cervical consistency index (CCI) and the risk of Cesarean delivery after planned induction of labor (IOL) at term.

METHODS

This was a prospective observational study of women with a term singleton pregnancy admitted for IOL due to maternal or fetal indication. Ultrasonographic images were obtained before IOL and CCI was calculated offline once recruitment was completed. The main outcome was defined as Cesarean delivery due to failed IOL or arrest of labor. Cesarean deliveries indicated due to maternal or fetal compromise (Van Dillen's grade 1 or 2) were excluded from analysis. Univariate statistical analysis was performed using Fisher's exact test and Student's t-test for categorical and continuous variables, respectively. Multivariate analysis was performed using logistic regression, including CCI and other variables related to the main outcome. Intraclass correlation coefficients were used to estimate intra- and interobserver agreement.

RESULTS

Of 510 women admitted for IOL during the study period and for whom image quality was adequate, 46 were excluded due to emergency Cesarean delivery leaving 464 pregnancies for analysis. Cesarean section due to failed IOL or arrest of labor was performed in 100/464 (21.6%) pregnancies. The mean CCI of women who underwent Cesarean delivery was not significantly different from that in those who had vaginal delivery after IOL (70.1 ± 12.3% vs 70.0 ± 13.1%; P = 0.94). Multivariate analysis also showed absence of statistical association between CCI and Cesarean delivery for failed IOL or arrest of labor. Intraclass correlation coefficients for intra- and interobserver agreement were 0.81 (95% CI, 0.66-0.89) and 0.86 (95% CI, 0.75-0.92), respectively.

CONCLUSION

CCI does not seem to be associated with the risk of Cesarean delivery after IOL. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Gestational age-related changes in shear wave speed of the uterine cervix in normal pregnancy at 12-35 weeks' gestation

Background This study aimed to analyze age-related changes in shear wave speed (SWS) of the normal uterine cervix. Methods We studied 362 women with a normal singleton pregnancy at 12-35 weeks' gestation. The SWS of the cervix was measured using transvaginal ultrasonography at the internal os region of the anterior cervix (IOA), posterior cervix (IOP) and cervical canal (IOC), and at the external os region of the anterior cervix (EOA), posterior cervix (EOP) and cervical canal (EOC). The following parameters were analyzed: (1) time trend of SWS of the individual sampling points, (2) comparison of SWS in the internal cervical region and SWS in the external cervical region, and (3) comparison of SWS between the internal and external cervical regions. Statistical analyses were performed using mixed-effects models. Results The SWS of IOP decreased in bilinear regression, with a critical change in the rate at 22 weeks, whereas the SWS of the remaining points decreased linearly. The estimated values of SWS of IOP at 84, 154 and 251 days were higher than those of IOA and IOC (P<0.001). The estimated values of SWS of IOP at 84 and 154 days were higher than those of EOP (P<0.001). Significant differences between IOP and EOP were shown until 244 days (P<0.05). The estimated value of SWS of IOC at 84 days was higher than that of EOC (P<0.001). Significant differences between IOC and EOC were shown until 210 days (P<0.05). Conclusion The SWS of the uterine cervix in pregnancy decreases with advancing gestation. The SWS of IOP had the highest value among the sampling points with unique characteristics.

How reliable is fetal occiput and spine position assessment prior to induction of labor?

OBJECTIVES

To assess the reliability of fetal occiput and spine position determination in nulliparous women prior to induction of labor (IOL), and to evaluate identification of fetal occiput and spine positions prior to IOL in the prediction of labor outcome.

METHODS

A series of 136 nulliparous women were recruited prospectively, immediately after the decision to perform IOL was made. Transabdominal ultrasound was performed to determine fetal head and spine positions. After at least 1 h, and prior to IOL, fetal occiput and spine positions were reassessed. Fetal occiput and spine positions were then compared between women who underwent vaginal delivery and those who delivered by Cesarean section.

RESULTS

On the first and second assessments, respectively, fetal occiput position was anterior in 55 (40.4%) and 62 (45.6%) women, transverse in 52 (38.2%) and 49 (36.0%) women, and posterior in 29 (21.3%) and 25 (18.4%) women, while fetal spine position was anterior in 58 (42.6%) and 52 (38.2%) women, transverse in 42 (30.9%) and 50 (36.8%) women, and posterior in 36 (26.5%) and 34 (25.0%) women. Discordance between the first and second assessments of fetal occiput position was identified in 34 (25.0%) women, whereas discordance of fetal spine position was observed in 40 (29.4%) women. The incidence of fetal occiput posterior position in women undergoing Cesarean section was comparable to that in the vaginal-delivery group (19 (18.8%) vs 6 (17.1%); P = 0.826), which was similarly the case for fetal posterior spine position (27 (26.7%) vs 7 (20%); P = 0.428). Women with fetal occiput posterior position had a longer induction-to-delivery interval in comparison to those with non-occiput posterior fetal position (1786 ± 805 vs 1347 ± 784 min; P = 0.013).

CONCLUSIONS

Fetal occiput and spine positions are dynamic in a considerable proportion of women undergoing IOL, and their assessment does not seem to correlate with mode of delivery. Occiput and spine position assessment in women prior to IOL is unlikely to be clinically useful. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Addition of Cervical Elastography May Increase Preterm Delivery Prediction Performance in Pregnant Women with Short Cervix: a Prospective Study

BACKGROUND

We investigated whether there is a difference in elastographic parameters between pregnancies with and without spontaneous preterm delivery (sPTD) in women with a short cervix (≤ 25 mm), and examined the ability of elastographic parameters to predict sPTD in those women.

METHODS

E-Cervix^TM (WS80A; Samsung Medison, Seoul, Korea) elastography was used to examine the cervical strain. Elastographic parameters were compared between pregnancies with and without sPTD. Diagnostic performance of elastographic parameters to predict sPTD ≤ 37 weeks, both alone and in combination with other parameters, was compared with that of cervical length (CL) using area under receiver operating characteristic curve (AUC) analysis.

RESULTS

A total of 130 women were included. Median gestational age (GA) at examination was 24.4 weeks (interquartile range, 21.4-28.9), and the prevalence of sPTD was 20.0% (26/130). Both the elastographic parameters and CL did not show statistical difference between those with and without sPTD. However, when only patients with CL ≥ 1.5 cm (n = 110) were included in the analysis, there was a significant difference between two groups in elasticity contrast index (ECI) within 0.5/1.0/1.5 cm from the cervical canal (P < 0.05) which is one of elastographic parameters generated by E-Cervix. When AUC analysis was performed in women with CL ≥ 1.5 cm, the combination of parameters (CL + pre-pregnancy body mass index + GA at exam + ECI within 0.5/1.0/1.5 cm) showed a significantly higher AUC than CL alone (P < 0.05).

CONCLUSION

An addition of cervical elastography may improve the ability to predict sPTD in women with a short CL between 1.5 and 2.5 cm.

Contraction of the levator ani muscle during Valsalva maneuver (coactivation) is associated with a longer active second stage of labor in nulliparous women undergoing induction of labor

BACKGROUND

The Valsalva maneuver is normally accompanied by relaxation of the levator ani muscle, which stretches around the presenting part, but in some women the maneuver is accompanied by levator ani muscle contraction, which is referred to as levator ani muscle coactivation. The effect of such coactivation on labor outcome in women undergoing induction of labor has not been previously assessed.

OBJECTIVE

The aim of the study was to assess the effect of levator ani muscle coactivation on labor outcome, in particular on the duration of the second and active second stage of labor, in nulliparous women undergoing induction of labor.

STUDY DESIGN

Transperineal ultrasound was used to measure the anteroposterior diameter of the levator hiatus, both at rest and at maximum Valsalva maneuver, in a group of nulliparous women undergoing induction of labor in 2 tertiary-level university hospitals. The correlation between anteroposterior diameter of the levator hiatus values and levator ani muscle coactivation with the mode of delivery and various labor durations was assessed.

RESULTS

In total, 138 women were included in the analysis. Larger anteroposterior diameter of the levator hiatus at Valsalva was associated with a shorter second stage (r = -0.230, P = .021) and active second stage (r = -0.338, P = .001) of labor. Women with levator ani muscle coactivation had a significantly longer active second stage duration (60 ± 56 vs 28 ± 16 minutes, P < .001). Cox regression analysis, adjusted for maternal age and epidural analgesia, demonstrated an independent significant correlation between levator ani muscle coactivation and a longer active second stage of labor (hazard ratio, 2.085; 95% confidence interval, 1.158-3.752; P = .014). There was no significant difference between women who underwent operative delivery (n = 46) when compared with the spontaneous vaginal delivery group (n = 92) as regards anteroposterior diameter of the levator hiatus at rest and at Valsalva maneuver, nor in the prevalence of levator ani muscle coactivation (10/46 vs 15/92; P = .49).

CONCLUSION

Levator ani coactivation is associated with a longer active second stage of labor.

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.

Effects of exercise during pregnancy in women with short cervix: Secondary analysis from the Italian Pessary Trial in singletons

OBJECTIVE

To evaluate effects of exercise during pregnancy in asymptomatic singleton pregnancies without prior spontaneous preterm birth (SPTB) but with short transvaginal ultrasound cervical length (TVU CL).

STUDY DESIGN

This is a secondary analysis of the Italian Pessary Trial for the Italian Preterm Birth Prevention (IPP) Working Group. In the original prospective randomized controlled trial asymptomatic singleton pregnancies without prior SPTB but with TVU CL ≤ 25 mm at 18 0/6-23 6/7 weeks were randomized into 1:1 ratio to either cervical pessary or no pessary. During their follow-up visits, women were asked about their activity. For the purpose of this secondary analysis, women were classified in the following groups, using the information obtained in the follow-up visit one month after randomization: 1) Exercise group, defined as women performing exercise ≥2 days a week for ≥20 min each day. 2) No exercise group, defined as women performing exercise <2 days a week for ≥20 min each day. The primary outcome of this secondary analysis was PTB < 37 weeks.

RESULTS

300 women were included in this analysis. 99 (33.0%) were included in the exercise group. 201 (67.0%) were included in the no exercise group. Of the 201 women in the no exercise group, 90 (44.8%) affirmed that they had reduced their activity after the diagnosis of short cervix despite the research staff recommendations, while the other 111 (55.2%) women performed a sedentary life style even before the diagnosis of short cervix. PTB < 37 weeks occurred in 22 women (22.2%) in the exercise group, and 66 women (32.8%) in the no exercise group (aOR 0.65, 95% CI 0.33-1.03).

CONCLUSION

In asymptomatic singleton pregnancies with short cervix, performing exercise ≥2 days a week for ≥20 min each day does not increase the risk of PTB but is indeed associated with a non-significant reduction in PTB < 37 weeks by 32%.

Midtrimester transvaginal ultrasound cervical length screening for spontaneous preterm birth in diamniotic twin pregnancies according to chorionicity

OBJECTIVE

To compare the mean transvaginal ultrasound (TVU) cervical length (CL) at midtrimester screening for spontaneous preterm birth in asymptomatic monochorionic diamniotic versus dichorionic diamniotic twin pregnancies STUDY DESIGN: This was a multicenter retrospective cohort study. Study subjects were identified at the time of a routine second trimester fetal ultrasound exam at 18 0/7-23 6/7 weeks gestation. We excluded women that received progesterone, pessary, or cerclage. Distribution of CL was determined and normality was examined. Mean of TVU CL were compared between monochorionic diamniotic and dichorionic diamniotic pregnancies. The relationship of TVU CL with gestational age (GA) at delivery and incidence of spontaneous preterm birth (SPTB) at different TVU CL cut offs were assessed. Incidence of short TVU CL, defined as TVU CL ≤30 mm, was also calculated in the two groups.

RESULTS

580 women with diamniotic twin pregnancies underwent TVU CL screening between 18 0/6 and 23 6/7 weeks. 175 (30.2%) were monochorionic diamniotic pregnancies, and 405 (69.8%) were dichorionic pregnancies. The demographic characteristics were similar on both groups. The mean GA at TVU CL was about 20 week in both groups. The mean TVU CL was significantly lower in the monochorionic diamniotic (32.8 ± 10.1) compared to the dichorionic (34.9 ± 8.6) group (MD -2.10 mm, 95% CI -3.91 to -0.29). TVU CL ≤30 mm was 16.6% (29/175) in the monochorionic group, and 11.9% (48/405) in the dichorionic group (aOR 1.48, 95% CI 1.03-2.43). Twins with a monochorionic diamniotic pregnancy had a significantly higher incidence of SPTB (53.1% vs 44.9%; aOR 1.22, 95% CI 1.22-1.79). For any given CL measured between 18 0-7 and 23 6/7 weeks, gestational age at delivery for monochorionic diamniotic pregnancies was about 2 weeks earlier compared to dichorionic pregnancies (MD -2.1 weeks; ANCOVA P < 0.001).

CONCLUSION

Monochorionic diamniotic twin pregnancies had a higher rate of spontaneous preterm birth than dichorionic diamniotic pregnancies. The higher rate of spontaneous preterm delivery in monochorionic pregnancies is associated with lower midtrimester TVU CL when compared to dichorionic pregnancies.

New techniques in evaluation of the cervix

The process of parturition is poorly understood, but the cervix clearly plays a key role. Because of this, recent research efforts have been directed at objective quantification of cervical remodeling. Investigation has focused on two basic areas: (1) quantification of tissue deformability and (2) presence, orientation, and/or concentration of microstructural components (e.g. collagen). Methods to quantify tissue deformability include strain elastography and shear wave elasticity imaging (SWEI). Methods to describe tissue microstructure include attenuation and backscatter. A single parameter is unlikely to describe the complexities of cervical remodeling, but combining related parameters should improve accuracy of cervical evaluation. This chapter reviews options for cervical tissue characterization.

Risk of spontaneous preterm birth in IVF-conceived twin pregnancies

OBJECTIVE

To compare the mean transvaginal ultrasound (TVU) cervical length (CL) at midtrimester in screening for preterm birth in in vitro (IVF)-conceived twin pregnancies versus spontaneously-conceived twin pregnancies.

METHODS

This was a retrospective cohort study. Potential study subjects were identified at the time of a routine second trimester fetal ultrasound exam at 18 0/7 to 23 6/7-week gestation. All women with twin diamniotic pregnancies screened with a single TVU CL for this trial were included. Mean TVU CLs were compared between IVF-conceived twin pregnancies and spontaneously-conceived twin pregnancies. The relationship of TVU CL with gestational age at delivery was assessed. Incidence of short TVU CL, defined as TVU CL ≤30 mm, was also calculated in the two groups. The primary outcome was the mean of TVU CL. Distribution of CL was determined and normality was examined in both groups Results: A total of 668 women with diamniotic twin pregnancies who underwent TVU CL screening between 18 0/6 and 23 6/7 weeks were included. 158 (23.7%) were IVF-conceived pregnancies, and 510 (76.3%) were spontaneously-conceived pregnancies. No women received progesterone, pessary, or cerclage for preterm birth prevention during pregnancy. The mean TVU CL was significantly lower in the IVF-conceived group (32.2 ± 10.5 mm) compared to the spontaneously-conceived group (34.1 ± 9.1 mm) (mean difference (MD) - 1.90 mm, 95%CI -3.72 to -0.08). The incidence of TVU CL ≤30 mm was 30.4% in the IVF-conceived group and 21.6% in the spontaneously-conceived group (adjusted odds ratio (aOR) 1.59, 95%CI 1.06-2.37). IVF-conceived twins had a significantly higher risk of spontaneous preterm birth <34 weeks (32.9 versus 21.2%; aOR 1.83, 95% confidence interval (CI) 1.23-2.71) and higher rate of delivery due to spontaneous onset of labor (64.5 versus 54.9%; aOR 1.50, 95%CI 1.03-2.17). For any given TVU CL measured between 18 0-7 and 23 6/7 weeks, gestational age at delivery for IVF-conceived twins was earlier by about 1 week on average compared with spontaneously-conceived twins.

CONCLUSIONS

The higher rate of spontaneous preterm birth in IVF-conceived twin pregnancies is predicted by lower midtrimester TVU CL, as well as by the lower gestational age at birth per any given CL in the IVF-conceived compared to the spontaneously-conceived twin pregnancies.

Cervical Evaluation: From Ancient Medicine to Precision Medicine

Since ancient times, cervical assessment for predicting timing of delivery has relied primarily on digital (subjective) assessment of dilatation, softening, and length. To date, transvaginal ultrasound cervical length is the only one of these parameters that meets criteria for a biomarker; no objective, quantitative measure of cervical dilatation or softening has gained clinical acceptance. This review discusses how the cervix has been assessed from ancient times to the present day and how a precision medicine approach could improve understanding of not only the cervix, but also parturition in general.

Cervical elastography during pregnancy: clinical perspectives

Uterine cervix is a part of the uterus responsible for maintaining pregnancy till term. As long as the cervix remains long and firm and its internal orifice (os) is closed, it can withstand enlargement of the uterine contents and resultant growing pressure. Mechanical properties of the cervix change during pregnancy; the cervix ripens prior to delivery, then effaces and dilates with contractions of the uterus. Ripening of the cervix can be assessed using the Bishop score and ultrasonographically determined length of the cervical canal and internal os. Consistency is one of the cervical properties that change during the course of the maturation process. Until recently, cervical consistency has been assessed only manually, but in 2007, the first report on elastographic imaging of the cervix during pregnancy has been published. Elastography presents the ability of a tissue to deform under pressure. The softer the tissue, the easier it changes its shape. Different methods of elastography are used - static, when tissue displacement in response to manual compression or physiological movements of vessels is measured, or dynamic, when the speed of shear wave propagation is determined. Irrespective of the method, elastography provides information on the internal os stiffness; this parameter, impossible for manual assessment, was shown to correlate with pregnancy outcome and is a strong predictor of preterm delivery or successful labor induction. Although elastography seems to be a highly promising diagnostic option, still no consensus has been reached regarding an optimal method for uterine cervix assessment, and virtually all previous studies of various elastographic methods produced highly satisfactory results. Future studies need to identify the most promising and objective elastographic method which may serve as a novel tool for pregnancy management, preventing adverse events, such as preterm delivery and unsuccessful labor induction.