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

Risk of caesarean delivery in labour induction: a systematic review and external validation of predictive models

BACKGROUND

Despite the existence of numerous published models predicting the risk of caesarean delivery in women undergoing induction of labour (IOL), validated models are scarce.

OBJECTIVES

To systematically review and externally assess the predictive capacity of caesarean delivery risk models in women undergoing IOL.

SEARCH STRATEGY

Studies published up to 15 January 2021 were identified through PubMed, CINAHL, Scopus and ClinicalTrials.gov, without temporal or language restrictions.

SELECTION CRITERIA

Studies describing the derivation of new models for predicting the risk of caesarean delivery in labour induction.

DATA COLLECTION AND ANALYSIS

Three authors independently screened the articles and assessed the risk of bias (ROB) according to the prediction model risk of bias assessment tool (PROBAST). External validation was performed in a prospective cohort of 468 pregnancies undergoing IOL from February 2019 to August 2020. The predictive capacity of the models was assessed by creating areas under the receiver operating characteristic curve (AUCs), calibration plots and decision curve analysis (DCA).

MAIN RESULTS

Fifteen studies met the eligibility criteria; 12 predictive models were validated. The quality of most of the included studies was not adequate. The AUC of the models varied from 0.520 to 0.773. The three models with the best discriminative capacity were those of Levine et al. (AUC 0.773, 95% CI 0.720-0.827), Hernández et al. (AUC 0.762, 95% CI 0.715-0.809) and Rossi et al. (AUC 0.752, 95% CI 0.707-0.797).

CONCLUSIONS

Predictive capacity and methodological quality were limited; therefore, we cannot currently recommend the use of any of the models for decision making in clinical practice.

TWEETABLE ABSTRACT

Predictive models that predict the risk of cesarean section in labor inductions are currently not applicable.

Can We Use the Bishop Score as a Prediction Tool for the Mode of Delivery in Primiparous Women at Term Before the Onset of Labor?

The Bishop score serves as an evaluation system performed by digital vaginal examination (DVE) to determine cervical ripening. The scoring system includes cervical dilatation, position, effacement and consistency of the cervix and fetal head station1. Nowadays, the Bishop score is frequently used as an important parameter for the prediction of successful induction of labor.

OBJECTIVE

Our objective was to demonstrate the role of the Bishop scoring system in prediction of the mode of delivery in primiparous women at term before the onset of labor.

METHOD

We included in this study unselected primiparous women at term, after 37 weeks of gestation, who presented to the Prenatal Diagnostic Unit (PDU) of the University Emergency County Hospital of Craiova. We excluded from the study multiparous patients, pregnancies with a planned Caesarean section delivery (CD), non-cephalic presentations and multiple pregnancies, twin pregnancies and those with detected fetal anomalies. The protocol included weekly DVEs until delivery for all patients, to determine the evolution of the Bishop score at term and in the week before delivery, and potential correlations with delivery outcome. To reduce clinical bias, the DVEs were performed by three experienced obstetricians involved in the research.

RESULTS

Statistical analysis yielded a 4 to 6 Bishop score in all weekly examinations. At 37 weeks of gestation, the majority of primiparous women had a Bishop score of 4, with no significant differences between the primiparous who delivered vaginally and the ones where Caesarean section was necessary. During the following weekly evaluations, we noted a slight turn to a Bishop score of 6 for most of them, without any significant differences between the two groups. However, at 41 weeks of gestation, there was a significant higher Bishop score in the group of primiparous women who delivered vaginally.

CONCLUSION

In our study, the use of the Bishop score failed as a prediction tool for the mode of delivery in primiparous women at term before the onset of labor, at a gestational age less than 40 weeks. Therefore, Bishop score should not be used to counsel regarding the probability of an uncomplicated vaginal delivery (VD) before the onset of labor.

Clinical and ultrasonographic parameters in assessment of labor induction success in nulliparous women

Purpose: Evaluation of simplified Bishop score and ultrasound cervicometry in the assessment of labor induction success in nulliparous women.Methods: Prospective cohort study included 146 nulliparous women with singleton pregnancy and indications for labor induction. Prior to labor induction, cervicometry and Bishop score were determined. Upon delivery, patients were classified as those delivered vaginally and by cesarean section (CS) after unsuccessful labor induction.Results: Bishop score >5 was found in 47.95% of vaginally delivered women and 12.33% of patients delivered by CS (p < .01). Cervicometry had appropriate findings in 34.2% of vaginally delivered women and 75.3% of those delivered by CS (p < .01). Bishop score (>5 versus ≤5) had lower sensitivity (52.05%) and specificity (12.33%) than cervicometry (good versus unfavorable findings) (sensitivity 65.75%, specificity 75.34%) for prediction of labor induction success. If Bishop score was ≤5, cervicometry had 50.0% sensitivity and 78.13% specificity, while if Bishop score was >5, 82.86% sensitivity and 55.56% specificity. Obtained model for predicting labor induction outcome in nulliparous women based on their clinical and ultrasonographical characteristics identified the Bishop score as the most important predictor.Conclusions: Study confirmed the usefulness of simplified Bishop score and ultrasound cervicometry in the assessment of labor induction success in nulliparous women.

Caesarean sections are associated with sonographic determined fetal size from the second trimester onwards

Human birth represents a critical and life-threatening event in the life of mother and child and is therefore of special importance for anthropological as well as public health research.

Study aims: to analyze the association patterns between fetal biometry and delivery modes from the first trimester onwards.

In this electronic medical record-based study, a dataset of 3408 singleton term birth taking place at the Viennese Danube hospital in Austria. was analyzed. Fetal biometry was reconstructed by the results of three ultrasound examinations carried out at the 11th/12th, 20th/21th and 32th/33thweek of gestation. In detail, crown-rump length, biparietal diameter, fronto-occipital diameter, head circumference, abdominal trans-verse diameter, abdominal sagittal diameter, abdominal circumference, and femur length were determined. Birth weight, birth length and head circumference were measured immediately after birth. Four delivery modes were compared: spontaneous vaginal birth, instrumental vaginal birth, planned cesarean section and emergency cesarean section.

The total cesarean section rate was 10.2%. Fetal biometry and newborn size differed significantly between the four delivery modes. From the second trimester onward, head circumferences were significantly larger (p=0.005) among fetuses delivered by instrumental delivery or emergency cesarean section than among fetuses delivered by spontaneous vaginal birth. The fetal abdominal dimensions during the third trimester were significantly largest (p=0.001) among fetuses delivered by emergency cesarean section. In comparison to spontaneous vaginal delivery the risk to require instrumental delivery increased significantly with increasing fetal head dimensions at the second (p=0.019) and third trimester(p=0.032) independent of maternal somatic factors. The risk of emergency CS increased significantly with increasing head dimensions (p=0.030) as well as abdominal dimensions (p=0.001) at the third trimester and newborn size (p=0.002), also independently of maternal somatic factors.

In general, larger fetuses are on an increased risk of experiencing instrumental delivery or emergency caesarean section. This association between fetal size and delivery mode is detectable from the second trimester onwards.

Term spontaneous trial of labor in nulliparous women of short stature: A hospitals-based cohort study

OBJECTIVES

To study the mode of delivery in a well selected cohort of short nulliparous women.

STUDY DESIGN

Hospitals-based cohort study between 2010-2018. The threshold (150 cm, i.e 2,3°p), for the short stature was chosen before the analysis by corresponding to - 2SD of the average population size distribution of all women who delivered over the same period: 2010-2018. Were included nulliparous women with a heigh ≤ 150 cm in term spontaneous labor with a single livung fetus in vertex presentation without malformation. Exclusion criteria were: multiparous, scarred uterus, twin pregnancy, induced labor, preterm delivery (< 37 W P), non-vertex pregnancy, medical termination of pregnancy, stillbirth, severe fetal malformations, pre-labor cesarean, and late dating ultrasound. The main outcome was the mode of delivery. Univariate and multivariate analysis adjusted on potential confounding variable were performed to investigate the risk of intrapartum CS.

RESULTS

178 nulliparous women were included. The mean height was 148 cm. The rate of spontaneous vaginal delivery, operative vaginal delivery a nd intrapartum CS were :35,4 %, 35,4 % and 29,2 % respectively. Intrapartum CS was performed during the first stage labor in 15 (28, 8 %) women and during the second stage in 37 (71, 2 %) women. An arrest of labor was significantly more frequent in the active labor than the early labor stage: 62,1 % vs. 33.3 % (p = 0, 02). In univarate analysis were associated with intrapartum CS : Gestational diabetes, birthweight> 3,5 kg, individual adjusted birthweight >90°p, occiput posterior, oxytocin use, cephalic circumference. After adjustment on birthplace and overweight (BMI over 25), only a birthweight > 3,5 kg remains associated with the risk of intrapartum CS (aOR4.3 ;95 %CI 1.96-10.2).

CONCLUSION

An attempt of vaginal birth is a reasonable option for short stature women. Maternal height could be included in the selection criteria for planned birth center or home birth. The customized gestational-related optimal weigh could be useful to identify large of gestational age fetus.

Ultrasound in labor admission to predict need for emergency cesarean section: a prospective, blinded cohort study

OBJECTIVE

To assess whether assessment with ultrasound could improve the detection of emergency cesarean section (ECS) in laboring women.

METHODS

Women who presented with symptoms of active labor or women in need of labor induction were invited to participate in the study. Women included in the study were evaluated with ultrasonography for fetal biometry and vaginal examinations for Bishop score assessment. The main aim in this study was determining factors associated with ECS due to fetal distress and obstructed labor.

RESULTS

No fetal biometry variable was associated with ECS due to any indication (fetal distress and obstructed labor combined) in the univariate analysis. In multivariate analyses, biometry variables were adjusted for Bishop score at admission and only abdominal circumference percentile showed a significant association with the odds of ECS due to any indication (OR:1.02, 95% CI: 1.01-1.03). Biparietal diameter and abdominal circumference variables were associated with the odds of ECS due to obstructed labor in both univariate and multivariate analyses (p < .05 for all). However, the predictive accuracy of biparietal diameter percentile (area under the curve (AUC): 0.55, 95% CI: 0.46-0.63) and abdominal circumference percentile (AUC: 0.56, 95% CI: 0.48-0.64) without adjunct variables were poor. Moreover, the addition of fetal biometry parameters to Bishop score did not improve the predictive accuracy of Bishop score.

CONCLUSION

Ultrasound assessment at admission, in addition to Bishop score assessment, did not significantly improve the prediction of ECS. Also, the fetal biometry alone had poor predictive capability for ECS. Routine ultrasound assessment at labor admission appears to be ineffective for predicting ECS.PrecisFetal biparietal diameter and abdominal circumference showed an association with emergency cesarean due to obstructed labor but the predictive accuracy of fetal biometry was low. Routine ultrasound examination at admission, in addition to Bishop score assessment, may not useful for assessing the risk of emergency section in unselected populations.

Can the Progression Angle before Labor Help to Predict Cesarean Section?

OBJECTIVE

The aim of this study was to predict cesarean section on a single visit at term using a combination of maternal history and ultrasound markers, including some new markers such as the progression angle used to assess intrapartum progress.

STUDY DESIGN

This was an observational prospective cohort study of singleton term pregnancies that included 575 women. The maternal history and ultrasound markers were obtained on a single visit at 37-38 weeks' gestation. Multivariable logistic regression was used for prediction of cesarean section.

RESULTS

Five hundred and seventy-five women were examined at a median gestational age of 38.3 weeks (range: 35.6-41.6) and a cesarean section was performed on 104 women (18%) - 24 for a fetal indication and 80 for a maternal indication. The risk of cesarean section increased with a previous cesarean section, assisted reproduction techniques, a higher estimated fetal weight, and a greater cervical length, and decreased with a greater maternal height, multiparity, and a wider progression angle. The detection rate for a 20% false positive rate was 69.9% for all cesarean sections, 54.2% for those with a fetal indication, and 77.2% for those with a maternal indication.

CONCLUSIONS

Assessment at 37-38 weeks' gestation of ultrasound markers such as the cervical length, progression angle, and estimated fetal weight, in combination with the maternal history, can predict a cesarean section in labor. Cesarean section for a maternal indication is better predicted than cesarean section for a fetal indication.

Is ultrasound measured fetal biometry predictive of intrapartum caesarean section for failure to progress?

BACKGROUND

There are global concerns regarding excessive caesarean rates, which could be reduced by identification of risk factors leading to preventative measures such as induction of labour.

AIMS

This study aims to describe the association between antenatal ultrasound and emergency caesarean section for: (i) failure to progress; (ii) other indications; and (iii) any indication.

MATERIALS AND METHODS

Women who had an ultrasound in pregnancy between 36^(+0/7) to 38^(+6/7) weeks at Royal Prince Alfred Hospital from January 2005 to June 2009 were included. Ultrasound parameters were linked to clinical parameters from the maternity database. Missing clinical data were imputed and multiple logistic regression performed.

RESULTS

Fetal biometry data were available for 2006 pregnancies. After adjusting for maternal age, height, body mass index, parity, previous caesarean section and diabetes, caesarean section for failure to progress was associated with estimated fetal weight (odds ratio (OR) 2.24 (95% CI: 1.76-2.84) per 500 g increase); or biparietal diameter (OR 1.51 (1.16-1.97) per 5 mm increase) and abdominal circumference (OR for the 4th quartile (>75th centile) compared with the 10-25th centile group was 2.09 (1.13-3.85)).* There were also non-linear associations between components of fetal biometry and caesarean section for fetal distress and for any indication.

CONCLUSIONS

Components of fetal biometry in the third trimester are associated with intrapartum caesarean section for failure to progress. These parameters could be incorporated into models to predict emergency caesarean section which could lead to implementation of preventative strategies. *[Corrections added on 29 January 2018, after first online publication, '(OR for the 4th quartile (>7th centile)' has been changed to '(OR for the 4th quartile (>75th centile)'.].

External cephalic version experiences in Korea

Objective

The aim of this study was to evaluate obstetric outcomes of external cephalic version (ECV) performed at or near term.

Methods

Single pregnant woman with breech presentation at or near term (n=145), who experienced ECV by one obstetrician from November 2009 to July 2014 in our institution were included in the study. Maternal baseline characteristic and fetal ultrasonographic variables were checked before the procedure. After ECV, the delivery outcomes of the women were gathered. Variables affecting the success or failure of ECV were evaluated.

Results

Success rate of ECV was 71.0% (n=103). Four variables (parity, amniotic fluid index, fetal spine position and rotational direction) were observed to be in correlation with success or failure of ECV. In contactable 83 individuals experienced successful ECV, cesarean delivery rates were 18.1%, 28.9%, and 5.3% in total, nulliparas, and multiparas, respectively.

Conclusion

Based on the results, ECV is proposed to be safe for both mother and her fetus. In addition, it is a valuable procedure that increases probability of vaginal delivery for women with breech presentation.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Association of fetal biparietal diameter with mode of delivery and perinatal outcome

OBJECTIVE

To determine the association between sonographic assessment of fetal biparietal diameter (BPD) and pregnancy outcome.

METHODS

This was a retrospective cohort study of pregnancies at 37-42 weeks of gestation which had antepartum sonographic measurement of BPD within 7 days before delivery. Eligibility was limited to singleton pregnancies with neither known structural or chromosomal abnormalities nor prelabor Cesarean delivery (CD). The association of BPD with outcome was analyzed using multivariate logistic regression, receiver-operating characteristics curves and stratification according to BPD quartiles.

RESULTS

In total, 3229 women were eligible for analysis, of whom 2483 (76.9%) had a spontaneous vaginal delivery (SVD), 418 (12.9%) underwent operative vaginal delivery (OVD) and 328 (10.2%) underwent CD. The mean BPD in the obstetric intervention groups (OVD and CD) was significantly higher than that in the SVD group (P < 0.001). After adjusting for confounders, increased BPD was an independent risk factor such that higher values of BPD were associated with progressively higher risk of obstetric intervention (adjusted odds ratio, 1.05 for each 1-mm increase in BPD (95% CI, 1.02-1.09)), but no clear cut-off value for obstetric intervention was found. The fourth quartile group (BPD ≥ 97 mm) was associated with a significantly lower SVD rate (P < 0.001) and higher OVD rate (P = 0.04), relative to the first (BPD 88-90 mm) and second (BPD 91-93 mm) quartile groups, with no apparent adverse impact on immediate neonatal outcome.

CONCLUSIONS

Increased BPD within the week prior to delivery is an independent risk factor such that higher values of BPD are associated with progressively higher risk of obstetric intervention; however, in our experience, no adverse neonatal outcome resulted from such intervention. Thus, increased BPD should not discourage a trial of vaginal delivery.

Prognostic models in obstetrics: available, but far from applicable

Health care provision is increasingly focused on the prediction of patients' individual risk for developing a particular health outcome in planning further tests and treatments. There has been a steady increase in the development and publication of prognostic models for various maternal and fetal outcomes in obstetrics. We undertook a systematic review to give an overview of the current status of available prognostic models in obstetrics in the context of their potential advantages and the process of developing and validating models. Important aspects to consider when assessing a prognostic model are discussed and recommendations on how to proceed on this within the obstetric domain are given. We searched MEDLINE (up to July 2012) for articles developing prognostic models in obstetrics. We identified 177 papers that reported the development of 263 prognostic models for 40 different outcomes. The most frequently predicted outcomes were preeclampsia (n = 69), preterm delivery (n = 63), mode of delivery (n = 22), gestational hypertension (n = 11), and small-for-gestational-age infants (n = 10). The performance of newer models was generally not better than that of older models predicting the same outcome. The most important measures of predictive accuracy (ie, a model's discrimination and calibration) were often (82.9%, 218/263) not both assessed. Very few developed models were validated in data other than the development data (8.7%, 23/263). Only two-thirds of the papers (62.4%, 164/263) presented the model such that validation in other populations was possible, and the clinical applicability was discussed in only 11.0% (29/263). The impact of developed models on clinical practice was unknown. We identified a large number of prognostic models in obstetrics, but there is relatively little evidence about their performance, impact, and usefulness in clinical practice so that at this point, clinical implementation cannot be recommended. New efforts should be directed toward evaluating the performance and impact of the existing models.

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.

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.

Can angle of progression in pregnant women before onset of labor predict mode of delivery?

OBJECTIVES

The angle of progression (AOP), measured by transperineal ultrasound, has been used to assess fetal head descent during labor. Our aim was to assess whether, before onset of labor, parous women have a narrower AOP than do nulliparous women and if a narrow AOP is associated with a higher rate of Cesarean delivery.

METHODS

In this prospective, observational study, we performed transperineal ultrasound in pregnant women not yet in labor at ≥ 39 weeks' gestation who delivered within 1 week of sonography. The AOP was compared as follows: in nulliparous women, between those who had a Cesarean section and those who delivered vaginally; and among women who delivered vaginally, between those who were nulliparous and those who were parous.

RESULTS

Included in the study were 100 nulliparous and 71 parous women. Among those who delivered vaginally (n = 161), the median AOP before onset of labor was narrower in parous than in nulliparous women (98° (interquartile range (IQR)), 90-107° vs 104° (IQR, 97-113°), P < 0.001). Among the 100 nulliparous women, (1) the median AOP before onset of labor was narrower in those who went on to deliver by Cesarean section (n = 9) than in those delivered vaginally (n = 91) (90° (IQR, 85.5-93.5°) vs 104° (IQR, 97-113°), P < 0.001); (2) an AOP ≥ 95° (derived from the receiver-operating characteristics curve) was associated with vaginal delivery in 99% of women; and (3) 89% (8/9) of women who delivered by Cesarean section had an AOP < 95°. Among the 71 parous women, only one delivered by Cesarean section and all of those with an AOP < 95° delivered vaginally.

CONCLUSION

A narrow AOP (< 95°) in non-laboring nulliparous women at term is associated with a high rate of Cesarean delivery. Parous women have a narrower AOP than do nulliparous women before the onset of labor; however, unlike in nulliparous women, a narrow AOP in parous women does not appear to be associated with Cesarean delivery and most parous women with such an angle go on to deliver vaginally.