Quantitative elastography of the cervix for predicting labor induction success

Prediction model for successful induction of labor by cervical strain elastography diagnosed at late-term pregnancy in nulliparous women: a prospective cohort study

BACKGROUND

The use of cervical strain elastography for nulliparous women during late-term pregnancy remains unclear. This study assesses the predictive value of late-term cervical strain elastography for successful induction of labor (IOL) in nulliparous women.

METHODS

This single-centered, prospective study included 86 patients undergoing IOL between January 2020 and March 2022. Univariate and multivariate analyses were conducted to identify predictive factors for successful IOL. The predictive values were assessed using the area under receiver operating characteristic (ROC) curves.

RESULTS

IOL was successful in 58 patients. The hardness ratio and cervical length were significantly associated with successful late-term IOL in nulliparous women. The predictive value of the combination of hardness ratio and cervical length was higher than that of cervical length alone.

CONCLUSIONS

The hardness ratio and cervical length assessed by cervical strain elastography during late-term pregnancy are predictors of the success of IOL in nulliparous women. The predictive value of the combination of hardness ratio and cervical length was higher than that of cervical length alone.

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.

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.

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.

Ultrasound examination of the cervix for predicting labor induction success: failed validation in a routine clinical setting of a successful previous pilot study

BACKGROUND

Induction of labor (IL) involves an overload of work in hospitals, as well as increased intervention. Traditionally, the Bishop score (BS) has been used to predict the outcome of a IL, but there is a growing interest in studying the predictive capacity of ultrasound variables.

OBJECTIVE

Validate a pilot predictive model performed by a single observer (Alvarez-Colomo C), based on clinical parameters and ultrasound parameters, that showed a significant association with the IL result, obtaining a correct prediction of vaginal delivery in 82.8%, with 15% false positive (FP). This validation was carried out under the usual conditions of clinical practice by four observers without distinction.

METHODS

A prospective, observational study was conducted between September 2010-July 2012, recruiting 231 single pregnancies (Group 2), who were to initiate the IL process, according to the methodology and inclusion criteria of the Alvarez-Colomo study (Group 1151 patients). The outcome variable was the method of delivery.

RESULTS

Only fetal head-perineal distance (FHPD), cervical length (CL) and BS showed significant association with the result of IL. After applying the logistic regression equation of the pilot study, the model developed by these four observers reached a predictive capacity of 70.74% (FP = 20%). Clinical characteristics were similar in both groups. Statistically significant differences were found between the two groups for: FHPD, posterior cervical angle (PCA) and funnel existence.

CONCLUSION

It has not been possible to validate the mathematical model of Alvarez's study in the daily conditions of clinical practice, probably due to differences in the ultrasound measurement of FHPD.

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.

The mechanical role of the cervix in pregnancy

Appropriate mechanical function of the uterine cervix is critical for maintaining a pregnancy to term so that the fetus can develop fully. At the end of pregnancy, however, the cervix must allow delivery, which requires it to markedly soften, shorten and dilate. There are multiple pathways to spontaneous preterm birth, the leading global cause of death in children less than 5 years old, but all culminate in premature cervical change, because that is the last step in the final common pathway to delivery. The mechanisms underlying premature cervical change in pregnancy are poorly understood, and therefore current clinical protocols to assess preterm birth risk are limited to surrogate markers of mechanical function, such as sonographically measured cervical length. This is what motivates us to study the cervix, for which we propose investigating clinical cervical function in parallel with a quantitative engineering evaluation of its structural function. We aspire to develop a common translational language, as well as generate a rigorous integrated clinical-engineering framework for assessing cervical mechanical function at the cellular to organ level. In this review, we embark on that challenge by describing the current landscape of clinical, biochemical, and engineering concepts associated with the mechanical function of the cervix during pregnancy. Our goal is to use this common platform to inspire novel approaches to delineate normal and abnormal cervical function in pregnancy.

Building a Prediction Model for Vacuum-Assisted Operative Vaginal Delivery Risk

AIM

The objective of this study was to evaluate the risk factors for operative vaginal delivery and to propose a new nomogram for predicting the risk.

METHODS

We retrospectively analyzed the data of 1,955 pregnancies that occurred in our clinic between the years 2007 and 2008. Included were singleton pregnancies with labor diagnosis after the 36th gestational week in which spontaneous or operative vaginal deliveries occurred. In this study, the operative delivery was carried out exclusively by vacuum extraction.

RESULTS

After univariate analysis and multivariate logistic regression stepwise model selection, maternal age, nulliparity, medically assisted procreation, gestational age at birth, male fetus, epidural analgesia and medical induction of labor were found to be the most predictive variables for operative vaginal delivery. Considering these factors we propose a new nomogram for an objectified determination of the risk of operative vaginal delivery.

CONCLUSIONS

The new nomogram we propose could be an important tool for an objectified determination of the risk of operative vaginal delivery by vacuum extraction in individualized patient counseling.

Innovative methods of cervical assessment and potential for novel treatment

A multitude of pathophysiologic pathways culminate in the final common denominator of cervical softening, shortening, and dilation that lead to preterm birth. At present, a variety of emerging technology aims to objectively quantify critical cervical parameters such as microstructural organization and softening of the cervix. If the nature and timing of cervical changes can be precisely identified, it should be possible to identify the causative upstream molecular processes and resultant biomechanical events associated with each unique pathway. This would promote molecular studies, ultimately leading to novel approaches to preterm birth prediction, novel treatments, and prevention.

Quantitative elastography of the uterine cervix as a predictor of preterm delivery

OBJECTIVE

To evaluate the correlation between preterm delivery before 37 weeks of gestation and ultrasound elastography strain measurement of cervical stiffness.

STUDY DESIGN

In this prospective study, 182 pregnant women were examined vaginally by ultrasound elastography from a mid-sagittal plane. Cervical length was measured and strain was calculated in four regions of interest on the anterior cervical lip. First, the software was validated by intraobserver variability. Second, strain and strain ratios were calculated with adjusted software presets and correlated to the outcome of spontaneous preterm delivery (sPTD).

RESULT

A total of 8928 regions of interest (ROIs) and 6696 ratios were evaluated. The median gestational age at examination was 26 ± 6.1 weeks. A median maternal age of 33 ± 5.6 and a medial parity of 1 ± 0.9 were observed. Intra-Class-Correlation values in validation phase ranged from 0.893 to 0.967. The prevalence of sPTD was 11.9%. Strain ratio Rselective was identified as the best predictor of preterm delivery. Rselective values >0.89 were associated with preterm delivery with a sensitivity of 0.59 and a specificity of 0.86 (odds ratio=1.474 for an increase of 0.1 in Rselective; P=0.002).

CONCLUSION

Ultrasound elastography strain measurement of cervical stiffness is correlated with the predictability of preterm delivery.

Quantitative elastography for cervical stiffness assessment during pregnancy

AIM

Feasibility and reliability of tissue Doppler imaging-(TDI-) based elastography for cervical quantitative stiffness assessment during all three trimesters of pregnancy were evaluated.

MATERIALS AND METHODS

Prospective case-control study including seventy-four patients collected between the 12th and 42nd weeks of gestation. The tissue strain (TS) was measured by two independent operators as natural strain. Intra- and interoperator intraclass correlation coefficient (ICC) agreements were evaluated.

RESULTS

TS measurement was always feasible and exhibited a high performance in terms of reliability (intraoperator ICC-agreement=0.93; interoperator ICC agreement=0.89 and 0.93 for a single measurement and for the average of two measurements, resp.). Cervical TS showed also a significant correlation with gestational age, cervical length, and parity.

CONCLUSIONS

TS measurement during pregnancy demonstrated high feasibility and reliability. Furthermore, TS significantly correlated with gestational age, cervical length, and parity.