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

A machine learning model to predict spontaneous vaginal delivery failure for term nulliparous women: An observational study

OBJECTIVE

This study aims to construct and evaluate a model to predict spontaneous vaginal delivery (SVD) failure in term nulliparous women based on machine learning algorithms.

METHODS

In this retrospective observational study, data on nulliparous women without contraindications for vaginal delivery with a singleton pregnancy ≥37 weeks and before the onset of labor from September 2020 to September 2021 were divided into a training set and a temporal validation set. Transperineal ultrasound was performed to collect angle of progression, head-perineum distance, subpubic arch angle, and their levator hiatal dimensions. The cervical length was measured via transvaginal ultrasound. The delivery methods were later recorded. Through LASSO regression analysis, indicators that can affect SVD failure were selected. Seven common machine learning algorithms were selected for model training, and the optimal algorithm was selected based on the area under the curve (AUC) to evaluate the effectiveness of the validation model.

RESULTS

Four indicators related to SVD failure were identified through LASSO regression screening: angle of progression, cervical length, subpubic arch angle, and estimated fetal weight. The Gaussian NB algorithm was found to yield the highest AUC (0.82, 95% confidence interval [CI] 0.65-0.98) during model training, and hence it was chosen for verification with the temporal validation set, in which an AUC of 0.79 (95% CI 0.64-0.95) was obtained with accuracy, sensitivity, and specificity rates of 80.9%, 72.7%, and 75.0%, respectively.

CONCLUSION

The Gaussian NB model showed good predictive effect, proving its potential as a clinical reference for predicting SVD failure of term nulliparous women before actual delivery.

Plasma Kallistatin and Progranulin as Predictive Biomarkers of Intraamniotic Inflammation, Microbial Invasion of the Amniotic Cavity, and Composite Neonatal Morbidity/Mortality in Women With Preterm Premature Rupture of Membranes

PROBLEM

To explore the clinical utility of nine inflammatory immune-, adhesion-, and extracellular matrix-related mediators in the plasma for predicting intraamniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) and composite neonatal morbidity and/or mortality (CNMM) in women with preterm premature rupture of membranes (PPROM) when used alone or in combination with conventional blood-, ultrasound-, and clinical-based factors.

METHODS OF STUDY

This retrospective cohort comprised 173 singleton pregnant women with PPROM (24 + 0 - 33 + 6 weeks), who underwent amniocentesis. Amniotic fluid was cultured for microorganisms and assayed for IL-6 levels. Plasma levels of AFP, CXCL14, E-selectin, Gal-3BP, kallistatin, progranulin, P-selectin, TGFBI, and VDBP were determined by ELISA. Ultrasonographic cervical length (CL) and neutrophil-to-lymphocyte ratio (NLR) were measured.

RESULTS

Multivariate logistic regression analyses revealed significant associations between (i) decreased plasma kallistatin levels and IAI/MIAC and (ii) decreased plasma progranulin levels and increased CNMM risk after adjusting for baseline variables (e.g., gestational age at sampling [or delivery] and parity). Using stepwise regression analysis, noninvasive prediction models for IAI/MIAC and CNMM risks were developed, which included plasma progranulin levels, NLR, CL, and gestational age at sampling, and provided a good prediction of the corresponding endpoints (area under the curve: 0.79 and 0.87, respectively).

CONCLUSIONS

Kallistatin and progranulin are potentially valuable plasma biomarkers for predicting IAI/MIAC and CNMM in women with PPROM. Particularly, the combination of these plasma biomarkers with conventional blood-, ultrasound-, and clinical-based factors can significantly support the diagnosis of IAI/MIAC and CNMM.

Comparing Transvaginal Ultrasound Measurements of Cervical Length to Bishop Score in Predicting Cesarean Section Following Induction of Labor: A Prospective Observational Study

INTRODUCTION

 Bishop score (BS) has been used to see the favorability of the cervix for induction of labor (IOL), but it has limitations in today's diverse patient population. We aimed to assess the predictive value of transvaginal ultrasound (TVUS) measurements of cervical length (CL) compared to BS in determining the likelihood of cesarean section (CS) following IOL.

METHODOLOGY

A prospective observational study was conducted on 120 women requiring IOL in a tertiary care hospital in central India. The inclusion criteria of the study were antenatal women more than 18 years of age, in need of IOL, having a singleton pregnancy with a gestational age of > 37 weeks as determined from the date of the last menstrual period and confirmed by sonographic measurements in the first trimester, presenting with a cephalic presentation, and having intact fetal membranes. Women with prior uterine scars and those unwilling to IOL were excluded from the study. TVUS was done just before induction. Statistical analyses were done to compare the predictive abilities of CL and BS for CS.

RESULTS

The mean age and gestation period were 25.96 years and 39 weeks 3 days, respectively. The majority of the study population comprised multigravida (69, 57.5%), followed by primigravida (47, 39.2%), and grand multigravida (≥ G5) (4, 3.3%). Post-maturity (34, 28.3%), preeclampsia (21, 17.5%), and intrahepatic cholestasis of pregnancy (17, 14.2%) were common indications for induction. The overall CS rate was 35.8% (43/120). Women with CS had lower BS (3.60 vs. 4.70, P = 0.010) and higher CL (31.5 mm vs. 23.4 mm, P < 0.001). CL exhibited an area under the curve (AUC) of 0.857, outperforming BS (AUC = 0.643) in predicting CS. Using a CL cutoff of 26.5 mm yielded sensitivity (79.1%), specificity (81.8%), and overall accuracy (80.8%).

CONCLUSIONS

TVUS measurement of CL (>26.5 mm) demonstrated superior predictive ability for CS following labor induction compared to BS (≤5). This study highlights the potential of CL measurement as an objective and reliable tool for optimizing decision-making in labor induction.

Assessment of different sonographic cervical measures to predict labor induction outcomes: a systematic review and meta-analysis

Background

Induction of labor (IOL) is a common obstetric approach to start or encourage uterine contractions to achieve a vaginal birth. It is recommended when continuing the pregnancy may be more dangerous for the mother or baby. Different ultrasonographic measures, such as cervical length, have been investigated as possible predictors of the outcomes of IOL. This meta-analysis aimed to assess the accuracy of ultrasound measurements in anticipating successful IOL.

Methods

The study conducted a thorough search on three databases (PubMed, Scopus, and Web of Science) until 04 March 2023, to find clinical studies published in English that reported different sonographic cervical measures and their ability to predict IOL outcomes. The chosen studies were stratified based on the type of indicator reported, and a meta-analysis was conducted to determine the best indicator for both successful and failed induction. The risk of bias and concerns about the applicability of the included studies was evaluated using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) method.

Results

This study analyzed 57 studies with 9,338 patients. Cervical length is moderately effective in predicting successful IOL, with pooled sensitivity (SN) and specificity (SP) of 0.67 and 0.70, respectively. However, cervical length had a pooled SN and SP of 0.70 and 0.61 for predicting failed IOL. The posterior cervical angle was found to have a higher pooled SN and SP of 0.79 and 0.73 for predicting successful IOL. Fetal head-perineum distance demonstrated moderate accuracy with a pooled SN, SP, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio, and area under the curve of 0.58, 0.66, 1.95, 0.36, 5.33, and 0.9992, respectively, for predicting successful IOL.

Conclusions

Fetal head-perineum distance was the most effective predictor for successful IOL compared to cervical length, which only had a moderate predictive ability. Shortening of cervical length was not a useful indicator for successful IOL. On the other hand, the posterior cervical angle was the most reliable factor for predicting failed induction. The study's findings can aid in developing more effective management strategies for IOL.

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.

Failed induction of labor in term nulliparous women with an unfavorable cervix: Comparison of cervical ripening by two forms of vaginal prostaglandins (slow-release pessary and vaginal gel)

OBJECTIVE

To compare the rate of failed induction after cervical ripening by two forms of vaginal prostaglandins.

MATERIAL AND METHODS

This two-year retrospective study (January 1, 2016, through December 31, 2017) in two tertiary maternity units included nulliparous women with a singleton fetus in cephalic presentation and an unfavorable cervix requiring labor induction for prolonged pregnancy. The principal endpoint was the rate of failed induction, defined by the performance of a cesarean delivery before 6 cm of dilation. Cervical ripening was initiated by prostaglandins for 24 h, using a slow-release pessary (unit A) or a vaginal gel (unit B). The care protocol of the two groups after the first 24 h were similar. The women's individual characteristics were compared between the two units. The rates of failed induction were then compared between the two units, first by univariate and then by multivariable analysis adjusted for the characteristics that differed significantly between the units.

RESULTS

Among the 17,217 women delivered in the two maternity units during the study period, 178 met our inclusion criteria (125 in unit A (slow-release pessary) and 53 in unit B (vaginal gel)). The rate of failed induction was similar: 21.6% in unit A (slow-release pessary) and 17.0% in unit B (vaginal gel) (P = 0.48). The multivariate analysis did not show any difference about failed induction, time from the onset of induction to delivery, and vaginal delivery rate within 24h.

CONCLUSION

The rate of failed induction of labor did not differ between slow-release pessary and vaginal gel.

Predictive factors for vaginal delivery by induction of labor in uncomplicated pregnancies at 40-41 gestational weeks: A Japanese prospective single-center cohort study

AIM

We investigated cervical parameters predictive of vaginal delivery in elective labor induction among women at 40-41 gestational weeks.

METHODS

This Japanese prospective single-center cohort study was conducted between July 2019 and June 2020. We enrolled women with an uncomplicated singleton pregnancy who underwent labor induction at 40-41 gestational weeks. We analyzed background characteristics and cervical parameters, including Bishop score, cervical length, posterior cervical angle, and changes in cervical parameters before and after cervical dilatation. The endpoint was the rate of vaginal delivery.

RESULTS

Of 142 eligible participants, all 24 multiparous women underwent vaginal delivery. Among the nulliparous women (n = 118), the following categories showed significantly higher rates of vaginal delivery: Bishop scores of ≥6 before and after dilatation, compared with Bishop score <6 (adjusted prevalence ratio (aPR) [95% confidence interval (CI)]; 1.58 [1.17-2.13] and 1.56 [1.13-2.14], respectively) and cervical length of <10 and 10-20 mm before dilation, compared with cervical length of >30 mm (aPR [95% CI]; 1.47 [1.00-2.15] and 2.13 [1.42-3.18], respectively). The posterior cervical angle and other background characteristics showed no significant associations. Furthermore, women with cervical lengths of ≥20 mm before and <20 mm after dilatation showed a higher rate of vaginal delivery, compared to cervical length of ≥20 mm even after dilatation (aPR [95% CI]; 1.95 [1.19-3.20]).

CONCLUSIONS

High Bishop score, short cervical length, and changes in cervical length with dilatation are potential independent predictors of vaginal delivery following elective labor induction in nulliparous women at 40-41 gestational weeks.

Factors Predicting Successful Vaginal Delivery Following Induction of Labor in Term Pregnancy

PURPOSE

This study was proposed to evaluate factors predicting a successful vaginal delivery following labor induction and develop induction prediction model in term pregnancy among Thai pregnant women.

PATIENTS AND METHODS

We conducted a retrospective cohort study using electronic medical records of 23,833 deliveries from April 2010 to July 2021 at tertiary care university hospital in Bangkok, Thailand. Univariate regression was performed to identify the association of individual parameters to successful vaginal delivery. Multiple logistic regression analysis of all possible variables from univariate analysis was performed to develop a prediction model with statistically significant of p value <0.05.

RESULTS

Of the total 809 labor-induced pregnancies, the vaginal delivery rate was 56.6%. Among predicting variables, history of previous vaginal delivery (aOR 5.75, 95% CI 3.701-8.961), maternal delivery BMI <25 kg/m² (aOR 2.010, 95% CI 1.303-3.286), estimated fetal weight <3500 g (aOR 2.193, 95% CI 1.246-3.860), and gestational age ≤39 weeks (aOR 1.501, 95% CI 1.038-2.173) significantly increased the probability of a successful vaginal delivery following labor induction. The final prediction model has been internally validated. Model calibration and discrimination were satisfactory with Hosmer-Lemeshow test P = 0.21 and with AUC of 0.756 (95% CI 0.695-0.816).

CONCLUSION

This study determined the pragmatic predictors for successful vaginal delivery following labor induction comprised history of previous vaginal delivery, maternal delivery BMI <25 kg/m², estimated fetal weight <3500 g, and gestational age ≤39 weeks. The final induction prediction model was well-performing internally validated prediction model to estimate individual probability when undergoing induction of labor. Despite restricted population, the predicting factors and model could be useful for further prospective study and clinical practice to improve induction outcomes.

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

Background

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

Method

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

Results

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

Conclusions

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

The Uterocervical Angle Combined with Bishop Score as a Predictor for Successful Induction of Labor in Term Vaginal Delivery

The objective of this study was to determine the value of uterocervical angle (UCA) in predicting successful induction of labor (IOL) in singleton pregnant women compared to the Bishop score and cervical length (CL). A total of 205 normal term, singleton labor-induction cases were analyzed. Successful IOL was defined as the onset of active labor of induction. A comparative analysis was performed to evaluate the effectiveness of UCA, Bishop score, and CL in predicting IOL. Compared to the non-successful IOL group, the women in the successful IOL group had significantly wider UCA (p = 0.012) and higher Bishop score (p = 0.001); however, the CL was not significantly different (p = 0.130). UCA alone did not perform better than the Bishop score when predicting successful IOL. However, UCA combined with the Bishop score showed higher performance in predicting IOL (combined UCA > 108.4° and favorable Bishop score as sensitivity of 44.6%, specificity of 96.0%, PPV of 96.2%, and NPV of 43.6; combined UCA > 108.4° or favorable Bishop score as sensitivity of 85.7%, specificity of 50.0%, PPV of 78.7%, and NPV of 61.9). In conclusion, UCA combined with Bishop score may be an effective sonographic method for predicting successful IOL.

Development and Validation of a Risk Prediction Model for Cesarean Delivery After Labor Induction

Objective: The goal of the study was to develop and validate a prediction model for cesarean delivery after labor induction that included factors known before the start of induction, unlike prior studies that focused on characteristics at the time of induction. Materials and Methods: Using 17,370 term labor inductions without documented medical indications occurring at 14 U.S. hospitals, 2007-2012, we created and evaluated a model predicting cesarean delivery. We assessed model calibration and discrimination, and we used bootstrapping for internal validation. We externally validated the model by using 2122 labor inductions from a hospital not included in the development cohort. Results: The model contained eight variables-gestational age, maternal race, parity, maternal age, obesity, fibroids, excessive fetal growth, and history of herpes-and was well calibrated with good risk stratification at the extremes of predicted probability. The model had an area under the curve (AUC) for the receiver operating characteristic curve of 0.82 (95% confidence interval 0.81-0.83), and it performed well on internal validation. The AUC in the external validation cohort was 0.82. Conclusion: This prediction model can help providers estimate a woman's risk of cesarean delivery when planning a labor induction.

Ultrasound cervical length measurement in prediction of labor induction outcome

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

The value of ultrasound measurement of cervical length and parity in prediction of cesarean section risk in term premature rupture of membranes and unfavorable cervix

AIM

To evaluate the influence of cervical length (CL) and parity as prediction factors for assessment of cesarean section (CS) risk in women with premature rupture of membranes (PROM) at term and unfavorable cervix, undergoing induction of labor (IOL) with dinoprostone intracervical gel.

METHODS

A prospective study involved 50 nulliparous and 51 multiparous women admitted for IOL. Pre-induction CL was measured and delivery outcomes were recorded.

RESULTS

Nulliparous women were younger than the multiparous (26.6±5.2 vs. 30.5±4.9; P<0.001) and had longer pre-induction CL (35.6±5.5 vs. 31.5±4.8; P<0.001) and induction-delivery interval (582 vs. 420 min; P<0.001). There was no difference in the mode of delivery, CS indications, Apgar score, neonatal weight, the rate of neonatal intensive care unit admission and perinatal death in respect of parity. CL was significantly shorter in vaginal vs. cesarean deliveries regardless of parity (31.4 vs. 38.8 mm, P<0.001, respectively). Cut-off values of CL for predicting CS were 37.5 mm in nulliparae and 34.5 mm in multiparae.

CONCLUSIONS

CLs of 37.5 mm in nulliparae and 34.5 mm in multiparae were determined as the cut-off values in predicting CS risk in women with PROM at term and unfavorable cervix.

Prediction of the risk of cesarean delivery after labor induction in twin gestations based on clinical and ultrasound parameters

AIMS

To develop a model based on clinical and ultrasound parameters to predict the risk of cesarean delivery after labor induction in near-term twin gestations.

METHODS

This retrospective cohort study included 189 consecutive women with twin gestations at ≥ 36.0 weeks scheduled for labor induction. The Bishop score and transvaginal ultrasonographic measurements of cervical length were obtained immediately before labor induction. Parameters studied included maternal age, height, weight, parity, gestational age, Bishop score, cervical length, epidural analgesia, method of conception, chorionicity and birth weight. Prostaglandin E2 (dinoprostone) and oxytocin were used for labor induction. Logistic regression analysis and receiver operating characteristic curve were used to generate a predictive model for cesarean delivery.

RESULTS

Fifty (26.5%) of the 189 women had cesarean deliveries. According to logistic regression analysis, maternal height (P = 0.004), parity (P = 0.005) and cervical length (P = 0.016), but not Bishop score (P = 0.920), were identified as independent predictors of cesarean delivery. A risk score based on a model of these three parameters was calculated for each patient. The model was shown to have an adequate goodness of fit (P = 0.201) and the area under the curve was 0.722, indicating fairly good discrimination.

CONCLUSIONS

Maternal height, parity and cervical length were independent parameters for predicting the risk of cesarean delivery after labor induction in twin gestations. A predictive model using these parameters may provide useful information for deciding whether or not to induce labor.

Non-Invasive Prediction of Histologic Chorioamnionitis in Women with Preterm Premature Rupture of Membranes

PURPOSE

To develop a model based on non-invasive clinical and ultrasonographic parameters for predicting the likelihood of subsequent histologic chorioamnionitis in women with preterm premature rupture of membranes (PPROM) and to determine whether the inclusion of invasive test results improves the predictive value of the model.

MATERIALS AND METHODS

This retrospective cohort study included 146 consecutive women presenting with PPROM (20-33 weeks). Transvaginal ultrasonographic assessment of cervical length was performed. Maternal serum C-reactive protein (CRP) levels and white blood cell (WBC) counts were measured after amniocentesis. Amniotic fluid (AF) obtained by amniocentesis was cultured, and interleukin-6 (IL-6) levels and WBC counts were determined. The primary outcome measure was histologic chorioamnionitis.

RESULTS

Risk scores based on serum CRP concentrations and gestational age (model 1) were calculated for each patient. The model was shown to have adequate goodness of fit and an area under the receiver operating characteristic curve (AUC) of 0.742. When including AF test results (e.g., AF IL-6 levels) in model 1, serum CRP concentrations were found to be insignificant, and thus, were excluded from model 2, comprising AF IL-6 levels and gestational age. No significant difference in AUC was found between models 1 and 2.

CONCLUSION

For women with PPROM, the newly developed model incorporating non-invasive parameters (serum CRP and gestational age) was moderately predictive of histologic chorioamnionitis. The inclusion of invasive test results added no predictive information to the model in this setting.

Prediction of impending preterm delivery based on sonographic cervical length and different cytokine levels in cervicovaginal fluid in preterm labor

AIMS

The aim of this study was to determine whether cervicovaginal interleukin (IL)-1β, IL-6 and IL-8 levels, and cervical length, alone or in combination, could predict impending preterm delivery in women with preterm labor and intact membranes.

MATERIAL AND METHODS

Cervicovaginal swab samples for IL-1β, IL-6, and IL-8 assays were taken from 136 consecutive women with preterm labor (23-34 weeks) before the transvaginal ultrasonography examination to measure cervical length. The primary outcome measurement was spontaneous preterm delivery within 7 days of sampling.

RESULTS

Spontaneous preterm delivery within 7 days occurred in 28.6% (39/136) of patients. Receiver-operator characteristic (ROC) curves indicated that cervical length (P < 0.001), cervicovaginal IL-6 (P < 0.001) and IL-8 (P = 0.014), but not IL-1β, could predict delivery within 7 days. According to the logistic regression analysis, high cervicovaginal IL-8 (P = 0.008) and IL-6 (P = 0.038) levels and short cervical length (P < 0.001) were significantly associated with delivery within 7 days, even after controlling for baseline variables. A combination of cervix length and cervicovaginal IL-8 increased the specificity of detecting delivery within 7 days to 92.8%, which was superior to either test alone (P < 0.001), but the sensitivity was only 56.4%.

CONCLUSION

In women with preterm labor, among the parameters assessed, cervicovaginal IL-6 and IL-8 and cervical length are the most important parameters in predicting impending preterm delivery. A combination of cervix length and cervicovaginal IL-8 appeared to be the best for predicting impending preterm delivery, but the relatively low sensitivity of this test may limit its clinical usefulness.

Definition of Failed Induction of Labor and Its Predictive Factors: Two Unsolved Issues of an Everyday Clinical Situation

OBJECTIVE

The objectives of this review were to identify the predictive factors of induction of labor (IOL) failure or success as well as to highlight the current heterogeneity regarding the definition and diagnosis of failed IOL.

MATERIALS AND METHODS

Only studies in which the main or secondary outcome was failed IOL, defined as not entering the active phase of labor after 24 h of prostaglandin administration ± 12 h of oxytocin infusion, were included in the review. The data collected were: study design, definition of failed IOL, induction method, IOL indications, failed IOL rate, cesarean section because of failed IOL and predictors of failed IOL.

RESULTS

The database search detected 507 publications. The main reason for exclusion was that the primary or secondary outcomes were not the predetermined definition of failed IOL (not achieving active phase of labor). Finally, 7 studies were eligible. The main predictive factors identified in the review were cervical status, evaluated by the Bishop score or cervical length.

DISCUSSION

Failed IOL should be defined as the inability to achieve the active phase of labor, considering that the definition of IOL is to enter the active phase of labor. A universal definition of failed IOL is an essential requisite to analyze and obtain solid results and conclusions on this issue. An important finding of this review is that only 7 of all the studies reviewed assessed achieving the active phase of labor as a primary or secondary IOL outcome. Another conclusion is that cervical status remains the most important predictor of IOL outcome, although the value of the parameters explored up to now is limited. To find or develop predictive tools to identify those women exposed to IOL who may not reach the active phase of labor is crucial to minimize the risks and costs associated with IOL failure while opening a great opportunity for investigation. Therefore, other predictive tools should be studied in order to improve IOL outcome in terms of health and economic burden.

Methods for assessing pre-induction cervical ripening

BACKGROUND

Induction of labour is the artificial initiation of labour in a pregnant woman after the age of fetal viability but without any objective evidence of active phase labour and with intact fetal membranes. The need for induction of labour may arise due to a problem in the mother, her fetus or both, and the procedure may be carried out at or before term. Obstetricians have long known that for this to be successful, it is important that the uterine cervix (the neck of the womb) has favourable characteristics in terms of readiness to go into the labour state.

OBJECTIVES

To compare Bishop score with any other method for assessing pre-induction cervical ripening in women admitted for induction of labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 March 2015) and reference lists of retrieved studies to identify randomised controlled trials (RCTs).

SELECTION CRITERIA

All RCTs comparing Bishop score with any other methods of pre-induction cervical assessment in women admitted for induction of labour. Cluster-RCTs were eligible for inclusion but none were identified. Quasi-RCTs and studies using a cross-over design were not eligible for inclusion. Studies published in abstract form were eligible for inclusion if they provided sufficient information.Comparisons could include the following.1. Bishop score versus transvaginal ultrasound (TVUS).2. Bishop score versus Insulin-like growth factor binding protein-1 (IGFBP-1).3. Bishop score versus vaginal fetal fibronectin (fFN).However, we only identified data for a comparison of Bishop score versus TVUS.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the trials for inclusion, extracted the data and assessed trial quality. Data were checked for accuracy.

MAIN RESULTS

We included two trials that recruited a total of 234 women. The overall risk of bias was low for the two studies. Both studies compared Bishop score withTVUS.The two included studies did not show any clear difference between the Bishop score and TVUS groups for the following main outcomes: vaginal birth (RR 1.07, 95% CI 0.92 to 1.25, moderate quality evidence), caesarean delivery (RR 0.81, 95% CI 0.49 to 1.34, moderate quality evidence), neonatal admission into neonatal intensive care unit (RR 1.67, 95% CI 0.41 to 6.71, moderate quality evidence). Both studies only provided median data in relation to induction-delivery interval and reported no clear difference between the Bishop and TVUS groups. Perinatal mortality was not reported in the included studies.For the review's secondary outcomes, the need for misoprostol for cervical ripening was more frequent in the TVUS group compared to the Bishop score group (RR 0.52, 95% CI 0.41 to 0.66, two studies, 234 women, moderate quality evidence). In contrast, there were no clear differences between the Bishop scope and TVUS groups in terms of meconium staining of the amniotic fluid, fetal heart rate abnormality in labour, and Apgar score less than seven. Only one trial reported median data on the induction-delivery interval and induction to active phase interval, the trialist reported no difference between the Bishop group and the TVUS group for this outcome. Neither of the included studies reported on uterine rupture.

AUTHORS' CONCLUSIONS

Moderate quality evidence from two small RCTs involving 234 women that compared two different methods for assessing pre-induction cervical ripening (Bishop score and TVUS) did not demonstrate superiority of one method over the other in terms of the main outcomes assessed in this review. We did not identify any data relating to perinatal mortality. Whilst use of TVUS was associated with an increased need for misoprostol for cervical ripening, both methods could be complementary.The choice of a particular method of assessing pre-induction cervical ripening may differ depending on the environment and need where one is practicing since some methods (i.e. TVUS) may not be readily available and affordable in resource-poor settings where the sequelae of labour and its management is prevalent.The evidence in this review is based on two studies that enrolled a small number of women and there is insufficient evidence to support the use of TVUS over the standard digital vaginal assessment in pre-induction cervical ripening. Further adequately powered RCTs involving TVUS and the Bishop score and including other methods of pre-induction cervical ripening assessment are warranted. Such studies need to address uterine rupture, perinatal mortality, optimal cut-off value of the cervical length and Bishop score to classify women as having favourable or unfavourable cervices and cost should be included as an outcome.

Clinical and sonographic parameters at mid-trimester and the risk of cesarean delivery in low-risk nulliparas

BACKGROUND

To examine the potential clinical and sonographic parameters at mid-trimester that predict the risk of intrapartum cesarean delivery at term among low-risk nulliparas.

METHODS

This prospective study recruited nulliparas with singleton low-risk pregnancies at 20.0-24.0 weeks. Sonographic measurement of the cervical length and fetal biometry was performed. The data collected at enrollment included maternal age, measured weight at first prenatal visit to the hospital, current weight, height, fetal biometric parameters, and cervical length. A multivariate analysis was conducted, with control for known intra- and postpartum confounding factors associated with cesarean delivery, including sex of the fetus.

RESULTS

Based on multivariate analyses of 652 women, of all variables at mid-trimester, only maternal height was significantly associated with increased risk of cesarean delivery (61, 9.4%), whereas for intra- or postpartum variables, induction of labor, epidural analgesia, male gender, and nightshift delivery showed statistically significant association with the risk of cesarean delivery.

CONCLUSIONS

Maternal height and fetal gender, as measured at mid-trimester, are potential independent predictors for the risk of intrapartum cesarean delivery at term in low-risk nulliparas; however, sonographic measurements of the cervical length, fetal biometric ratio, maternal age, and current weight at mid-trimester were not predictive of cesarean delivery at term. © 2014 Wiley Periodicals, Inc. J Clin Ultrasound 43:235-242, 2015.

The role of sonographic cervical length in labor induction at term

The purpose of this study is to review the literature examining the role of ultrasound in the induction of labor. Databases including Ovid, PubMed, Web of Science, Google Scholar, and UpToDate were searched and current guidelines from the SOGC, the ACOG, the RCOG, and the RANZCOG were reviewed. Although studies have not demonstrated the superiority of cervical sonography to the Bishop score, the evidence indicates that sonography could be useful in planning induction of labor, significantly reducing the need for cervical ripening agents. A more comprehensive method integrating both sonography and digital exam may be more appropriate.

Relationship between detection of the cervical gland area during the late third trimester and necessity for induction of labor to prevent post-term delivery

OBJECTIVES

With the maturation of the cervical canal during pregnancy, the cervical gland area (CGA) as observed on transvaginal ultrasonography is gradually obscured. The aim of this study was to elucidate the significance of CGA in the late third trimester as a determinant of the outcome of labor.

METHODS

We investigated 123 primiparous women with singleton pregnancies at 36-41 weeks' gestation. The women were divided into two groups: a normal delivery group (93 women), which had vaginal delivery without medical intervention, and an induction of labor group (30 women), which required induction of labor after 41 weeks and 0 day. At outpatient prenatal checkups, the Bishop score (BS) was assessed by pelvic examination, and cervical length (CL) and CGA were evaluated by transvaginal ultrasonography. The relationship between each parameter and induction of labor was retrospectively determined and compared.

RESULTS

Time-dependent assessment of each outcome determinant showed that the CGA detection rate was higher and the CL was longer in the induction of labor group from 3 weeks to 1 week before delivery at a significant level (P < 0.05); however, the BS was significantly lower in the induction of labor group only at 1 week before delivery (P < 0.05). When multiple logistic regression analysis of the necessity of induction of labor was conducted using BS, CL, and CGA parameters as explanatory variables at 1 week before delivery, CGA alone was shown to be an independent predictor of induction of labor (OR = 6.1, 95 % CI 2.3-16.2).

CONCLUSION

The present study suggests that in the late third trimester, evaluation of CGA with transvaginal ultrasonography is most useful in predicting the necessity of induction of labor to prevent post-term delivery.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Prediction of successful labor induction using transvaginal sonographic cervical measurements

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical parameters for prediction of successful labor induction after application of intravaginal dinoprostone in nulliparous Chinese women

BACKGROUND

The aim of this study was to compare the possible clinical parameters for prediction of successful labor induction in Chinese nulliparous women.

MATERIAL/METHODS

A retrospective, observational trial of labor induction was performed, using a single dose of 10 mg controlled-release dinoprostone for preinduction cervical ripening in 127 nulliparous women (gestational age 38-42 weeks, singleton cephalic presentation). The characteristics of the women with successful labor induction (defined as vaginal delivery achieved on the day of admission; n=80) and failed labor induction (n=47) were compared.

RESULTS

The main differences observed between the groups were gravidity (P<0.05), induction-active labor interval (5.16±2.98 vs. 8.40±3.41; P<0.05) and birth weight (3421.11±368.14 vs. 3566.36±345.16; P<0.05). Logistic regression demonstrated that gravidity (P<0.05) and induction-active labor interval (P<0.05), but not Bishop score, were significant and independent contributing factors for successful labor induction. In the receiver operating characteristic curves for the prediction of successful labor induction, the best cut-off value for gravidity was 3 (95% confidence interval [CI] 0.64-0.83, P=0.000), and the best cut-off value for the induction-active labor interval was 7.96 (95%CI 0.66-0.85, P=0.000).

CONCLUSIONS

Less gravidity and shorter induction-active labor interval predict successful labor induction with reasonable accuracy.

Prediction of imminent preterm delivery in women with preterm premature rupture of membranes

AIMS

To develop a model based on non-invasive clinical parameters to predict the probability of imminent preterm delivery (delivery within 48 h) in women with preterm premature rupture of membranes (PPROM), and to determine if additional invasive test results improve the prediction of imminent delivery based on the non-invasive model.

METHODS

Transvaginal ultrasonographic assessment of cervical length was performed and maternal serum C-reactive protein (CRP) and white blood cell (WBC) count were determined immediately after amniocentesis in 102 consecutive women with PPROM at 23-33+6 weeks. Amniotic fluid (AF) obtained by amniocentesis was cultured and interleukin-6 (IL-6) levels and WBC counts were determined.

RESULTS

Serum CRP, cervical length, and gestational age were chosen for the non-invasive model (model 1), which has an area under the curve (AUC) of 0.804. When adding AF IL-6 as an invasive marker to the non-invasive model, serum CRP was excluded from the final model (model 2) as not significant, whereas AF IL-6, cervical length, and gestational age remained in model 2. No significant difference in AUC was found between models 1 and 2.

CONCLUSIONS

The non-invasive model based on cervical length, gestational age, and serum CRP is highly predictive of imminent delivery in women with PPROM. However, invasive test results did not add predictive information to the non-invasive model in this setting.

Comparison between sonographic cervical length and Bishop score in preinduction cervical assessment: a randomized trial

OBJECTIVE

To compare sonographically measured cervical length with the Bishop score in determining the requirement for prostaglandin administration for preinduction cervical ripening in nulliparae at term.

METHODS

One hundred and fifty-four women with singleton pregnancies at term who were scheduled for induction of labor were randomly assigned to receive prostaglandin for preinduction cervical ripening based on the Bishop score or sonographic cervical length. A cervix unfavorable for treatment with prostaglandin for preinduction cervical ripening was defined as having either a Bishop score of ≤ 4 or a cervical length of ≥ 28 mm. The primary outcome measures were induction success (defined as an ability to achieve the active phase of labor) and the percentage of patients treated with prostaglandin for preinduction cervical ripening.

RESULTS

The two groups were similar with respect to maternal demographics, gestational age, cervical length, and Bishop score. The rates of induction success and Cesarean delivery, the interval to active phase of labor, and the interval to delivery were also similar in the two groups. However, in the transvaginal ultrasound group (n = 77), prostaglandin was administered to only 36% of the nulliparae compared with 75% of those in the Bishop score group (n = 77) (P < 0.0001).

CONCLUSION

In comparison with the Bishop score, the use of sonographic cervical length for assessing the cervix prior to induction of labor can reduce the need for prostaglandin administration by approximately 50% without adversely affecting the outcome of induction in nulliparae at term if the cut-off values used are a Bishop score of ≤ 4 and a cervical length of ≥ 28 mm.

Non-invasive prediction of intra-amniotic inflammation in women with preterm labor

OBJECTIVE

To develop a model based on non-invasive variables to predict the probability of intra-amniotic inflammation in women with preterm labor and intact membranes.

METHODS

Transvaginal ultrasonography and digital examination for the assessment of cervical length and cervical dilatation were performed, and maternal blood was collected for the determination of C-reactive protein and white blood cell (WBC) count immediately after amniocentesis in 153 consecutive women with preterm labor. Amniotic fluid obtained by amniocentesis was cultured for aerobic and anaerobic bacteria and mycoplasmas, and the WBC was determined. Intra-amniotic inflammation was defined as an elevated amniotic fluid interleukin-6 concentration (> 2.6 ng/mL). Receiver-operating characteristics (ROC) curves and logistic regression analysis were used for statistical analysis.

RESULTS

The prevalence of a positive amniotic fluid culture was 7.2% (11/153) and the prevalence of intra-amniotic inflammation was 19.6% (30/153). The final logistic regression model was based on non-invasive clinical variables, including gestational age at assessment, cervical length and maternal blood WBC count, which were the best predictors of intra-amniotic inflammation. The model was shown to have an adequate goodness of fit (P = 0.754), and the area under the ROC curve was 0.724, indicating reasonably good discrimination.

CONCLUSION

In women with preterm labor and intact membranes, the risk for intra-amniotic inflammation can be predicted non-invasively with a risk score based on gestational age, cervical length and maternal blood WBC count.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Outcome of induction of labour using maternal characteristics, ultrasound assessment and biochemical state of the cervix

OBJECTIVE

To assess pre-induction sonographic, digital examination and biochemical changes in the cervix to predict induction outcome.

METHODS

Transvaginal and abdominal scans were performed in 460 women at 37-41 weeks of gestation to determine cervical length (CL), posterior cervical angle (PCA) and foetal occipital position. The Bishop Score (BS) and the absence/presence of phosphorylated form of insulin-like growth factor-binding protein-1 (phIGFBP-1) in cervical secretions were assessed. Independent parameters significantly associated with a vaginal delivery were identified.

RESULTS

A total of 340 (73.9%) women achieved a vaginal delivery following induction. Multivariate analysis indicated that significant independent predictors of vaginal delivery were CL (adjusted odds ratio [AOR]: 0.59, 95% confidence interval [CI]: 0.45-0.79), PCA (AOR: 1.89, 95% CI: 1.09-3.28) and multiparae (AOR: 10.02, 95% CI: 5.10-19.69). For a specificity of 75%, the sensitivity for prediction of vaginal delivery using the BS, the CL and the multivariate model using the identified significant independent predictors were 37.1, 46.8 and 68%, respectively.

CONCLUSION

The combination of sonographic assessment of the cervix and maternal characteristics was superior to the either BS or CL alone in the prediction of the induction outcome. Inclusion of the absence/presence of phIGFBP-1 did not further improve induction outcome.

Body mass index, Bishop score, and sonographic measurement of the cervical length as predictors of successful labor induction in twin gestations

AIMS

To evaluate the predictive value of body mass index (BMI), Bishop score, and sonographic measurement of cervical length for predicting successful labor induction (defined as an ability to achieve the active phase of labor corresponding to a cervical dilatation of > or =4 cm within 12 h of initiating oxytocin) in near-term twin gestations.

METHODS

This prospective, observational study enrolled 72 consecutive women with twin gestations at >36.0 weeks' gestation who were scheduled for induction of labor. Transvaginal ultrasound for measurement of the cervical length was performed and the Bishop score was determined by digital examination. The BMI was calculated based on the weight and height at the time of induction.

RESULTS

Labor induction was successful in 63% (45/72) of women. The mean BMI was significantly lower in women who had successfully induced labor, but no significant differences existed with respect to the mean cervical length, median Bishop score, proportion of parous and nulliparous women, and the mean total birth weight of the twin pairs between the two patient groups. Multiple logistic regression demonstrated that only BMI provided a significant contribution in predicting successful labor induction.

CONCLUSIONS

BMI independently predicted the success of labor induction in twin gestations but the sonographic measurement of the cervical length and Bishop score had poor predictive values for successful induction.

Prediction of failed labor induction in parous women at term: role of previous obstetric history, digital examination and sonographic measurement of cervical length

AIM

To examine the predictive value of previous obstetric history, Bishop score, and sonographic measurement of cervical length for predicting failed induction of labor in parous women at term.

METHODS

This prospective observational study enrolled 110 consecutive parous women at term with singleton gestations scheduled for the induction of labor. Transvaginal ultrasound for measurement of cervical length was performed and the Bishop score was assessed using digital examination. Univariate and multivariate analyses were used for statistical analysis.

RESULTS

Labor induction failed in 15 women (14%). In terms of previous obstetric history, women with only previous mid-trimester loss or preterm delivery had a significantly higher risk of failed labor induction than those with at least one previous term delivery. Logistic regression demonstrated that previous obstetric history and the Bishop score, but not cervical length, were found to be significant and independent contributing factors for failed labor induction. In the receiver operating characteristic curves, the best cut-off value of the Bishop score for the prediction of failed labor induction was 3, with a sensitivity of 73% and a specificity of 44%.

CONCLUSIONS

The previous obstetric history (i.e., only previous mid-trimester loss or preterm delivery) and the Bishop score independently predicted the failure of labor induction in parous women; however sonographic measurement of the cervical length appeared to have a poor predictive value for the risk of failed induction.

Transvaginal ultrasonographic measurement of cervical length in predicting intra-amniotic infection and impending preterm delivery in preterm labor: a comparison with amniotic fluid white blood cell count

AIMS

To determine whether sonographic measurement of cervical length predicts intra-amniotic infection and impending preterm delivery (within 7 days of amniocentesis) in women with preterm labor and intact membranes, and to compare the predictability with that of amniotic fluid (AF) white blood cell (WBC) count.

METHODS

Transvaginal ultrasonographic assessment of cervical length was performed immediately after amniocentesis in 67 consecutive women with preterm labor. AF obtained by amniocentesis was cultured for aerobic and anaerobic bacteria and for Mycoplasmas, and WBC count was determined.

RESULTS

Patients with a positive AF culture had a significantly shorter median cervical length, higher median AF WBC count, and lower median gestational age at delivery than did those with a negative AF culture. Multivariate analysis indicated that only the AF WBC count bears a significant relationship with the presence of intra-amniotic infection, whereas only cervical length correlates with impending preterm delivery.

CONCLUSIONS

Transvaginal sonographic measurements of cervical length are a valuable method for predicting intra-amniotic infection as well as impending preterm delivery in women with preterm labor. However, in comparison with AF WBC, cervical length is less predictive for intra-amniotic infection, whereas cervical length demonstrates better predictability of impending preterm delivery.