Preinduction cervical assessment

Systems of quantifying and scoring cervical factors have been sought for years to predict the duration of labor and to determine which patients may successfully and safely undergo induction of labor. Early methods of cervical assessment generally attempted to classify patients as having favorable or unfavorable cervices based on dichotomous variables. Since then, obstetricians have begun to appreciate the usefulness of having a single score derived from the degree of ripeness of several cervical characteristics. The scoring system that has become most prevalent is the Bishop score. This system and its modifications take into account the dilation, effacement, consistency, and position of the cervix in addition to the station of the presenting part. Many have evaluated and confirmed the validity of the Bishop score. Among the factors considered in assigning the score, the strongest association with successful labor seems to be with cervical dilation. The Bishop score has been criticized for not attributing more significance to cervical dilation. However, despite this criticism, none of the modifications to the original scoring system have been shown to improve predictability. More recently, the use of ultrasound assessment of the cervix has been suggested to improve prediction of the success of labor induction. However, convincing evidence that this technique provides significant additional information when compared to digital examination is lacking. The Bishop score would seem to be the best and most cost-effective method currently available to assess the cervix and predict the likelihood of success of labor induction and the duration of such an induction.     

Comparison of ultrasonographic cervical length and the Bishop score in predicting successful labor induction

BACKGROUND: The aim of this study was to compare the performance of the Bishop score and transvaginal ultrasonography to predict successful labor induction, and to estimate the most useful cut-off points for the two methods. METHODS: The five components of the Bishop score were assessed by digital examination and cervical length was measured by transvaginal ultrasonography in 177 women with a single pregnancy, 36-42 weeks of gestation, and a live fetus in cephalic presentation before induction of labor. RESULTS: Multiple regression analysis showed that the Bishop score, cervical length, and parity provided independent contribution in the prediction of the likelihood of delivering vaginally within 60 h. The only component of the Bishop score that was independently predictive of the probability of vaginal delivery within 60 h was station. The best cut-off points for predicting successful induction using receiver operating characteristic curves were 24 mm for cervical length and 4 for the Bishop score. Cervical length was a better predictor than the Bishop score (sensitivity and specificity of 66 and 77% versus 77 and 56%, respectively). Kaplan-Meier survival curves showed that cervical length was the best discriminator of successful induction. CONCLUSION: Measurement of cervical length by transvaginal ultrasonography is a better predictor of success in labor induction with both topical prostaglandin and oxytocin.     

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

OBJECTIVE: The purpose of this study was to evaluate whether biochemical (fetal fibronectin assay) or biophysical (cervical assessment by transvaginal ultrasound) tests may have more value than digital examination in predicting successful induction of labor at term. STUDY DESIGN: The study enrolled prospectively 134 women undergoing labor induction at term caused by several obstetric conditions. All participants submitted to digital examination, fetal fibronectin assay, and transvaginal ultrasound for measurement of the cervical length and detection of funneling. The performance of each test in predicting delivery within 24 hours of labor induction was evaluated. Cox multiple regression analysis was performed to identify, among clinical and laboratory tests, which variables were independently associated with the duration of the latent phase and with the total duration of induced labor. RESULTS: The likelihood ratios for positive results (predicting that delivery would occur within 24 hours) were 6.61 (95% CI, 1.7-25.8) for a positive obstetric history (previous vaginal delivery), 2.61 (95% CI, 1.6-4.3) for a "favorable" digital examination, 1.41 (95% CI, 0.9-2.2) for a positive fetal fibronectin test, 1.61 (95% CI, 0.9-3.0) for cervical length, and 2.20 (95% CI, 1.1-4.4) for the presence of funneling at transvaginal ultrasound. The likelihood ratios for negative results were 1.81 (1.3-2.5) for obstetric history, 4.34 (2.5-7.7) for digital examination, 1.41 (0.9-2.1) for fetal fibronectin, 1.29 (1.0-1.7) for cervical length, and 1.48 (1.1-2.0) for funneling. On multiple regression, the only variables independently associated with the duration of the latent phase and with the total duration of induced labor were obstetric history and digital examination. CONCLUSION: Only obstetric history and digital examination predicted accurately vaginal delivery within 24 hours and were independently associated with labor duration. Fetal fibronectin and ultrasound measurements failed to predict accurately the outcome of induced labor.     

Transvaginal ultrasound and digital examination in predicting successful labor induction.

OBJECTIVE: To compare transvaginal ultrasound and digital cervical examination in predicting successful induction in post-term pregnancy. METHODS: Transvaginal ultrasound and digital vaginal examinations were performed on 122 women at 41 or more weeks' gestation, immediately before labor induction. Ultrasound assessments of cervical length, dilatation, and presence of funneling were compared with the components of the Bishop score. The primary outcome was the rate of vaginal delivery. Secondary outcomes assessed included the rates of active labor in 12 hours, vaginal delivery in 12 and 24 hours, mean duration of latent phase, and induction to vaginal delivery interval. Linear and multiple logistic regression models were generated to identify factors independently associated with successful induction. RESULTS: No ultrasound characteristic predicted primary or secondary outcomes. Bishop score (odds ratio [OR] 2.98, 95% confidence interval [CI] 1.71, 5.20), cervical position (OR 4.35, 95% CI 1.41, 12.50), and maternal age (OR 1.15, 95% CI 1.01, 1.30) independently predicted vaginal delivery. Maternal weight (OR 0.96, 95% CI 0.94, 0.98), cervical dilatation (OR 6.08, 95% CI 1.70, 21.68), and effacement (OR 2.34, 95% CI 1.16, 4.73) independently predicted active labor in 12 hours. Independent predictors of vaginal delivery in 12 hours were induction method (P <.001), cervical dilatation (OR 11.16, 95% CI 3.17, 39.29), gravidity (OR 2.06, 95% CI 1.13, 3.77), and maternal weight (OR 0.96, 95% CI 0.93, 0.99). Cervical effacement (OR 2.70, 95% CI 1.59, 4.57) and parity (OR 7.10, 95% CI 2.22, 22.72) independently predicted vaginal delivery in 24 hours. Maternal weight, cervical position, and cervical dilatation were independently associated with latent phase labor duration. Factors independently associated with length of induction to delivery interval were parity, cervical effacement, and maternal weight. CONCLUSION: Transvaginal ultrasound does not predict successful labor induction in post-term pregnancy as well as digital cervical examination.     

The use of sonographic cervical length assessment for the prediction of time from induction to delivery

Objective: The objective of this study is to investigate the role of trans-vaginal cervical length measurement in the prediction of the interval to successful vaginal delivery after induction of labor with balloon catheter.

Methods: In this prospective study of cervical length measurement before induction of labor, singleton pregnancies that underwent induction of labor between 37 and 42 weeks of gestation were included. The data collected included trans-vaginal sonographic cervical measurements followed by digital cervical assessment. Bishop score was used to quantify digital assessment (before induction of labor).

Results: During the study period, 71 patients were included in the study. A statistically significant linear correlation was found between sonographic cervical length prior to induction of labor and the time of delivery (Pearson correlation 0.335; p values 0.005). Of the 57 vaginal deliveries, 27 patients had a cervical length of less than 28?mm. Patients with a cervical length of less than 28?mm had a significantly shorter time to delivery compared to patients with more than 28?mm length (20.4 versus 28.7, respectively; p value?=?0.019). Cervical length of 28?mm remained significantly correlated even after performing several logistic regression models in order to control for confounders such as parity and age. In addition, a correlation was found between Bishop scores of above 7 to the time to delivery.

Conclusions: Cervical length is correlated linearly to the time interval between induction of labor and delivery. A cervical length of less than 28?mm was found to be statistically significant in predicting a shorter time to delivery.     

A comparison of early and delayed induction of labor with spontaneous rupture of membranes at term

The management of women with spontaneous rupture of membranes at term in the absence of labor and with a cervix unfavorable for induction of labor is controversial. In this randomized study of 182 patients, we report the effects of delayed versus early induction of labor on maternal and neonatal outcome. Qualifying patients not in labor at 6 hours after spontaneous rupture of membranes were randomized to either immediate oxytocin induction (86 women) or expectant management with oxytocin induction at 24 hours if labor had not occurred spontaneously (96 women). The cesarean section rate did not differ between the two groups. Women in the delayed group had significantly longer hospitalization (P less than .003), and their infants were significantly more likely to receive antibiotics (P = .006). Infectious morbidity (positive cultures or x-ray-documented pneumonia) occurred in five of the neonates in the delayed group, all of whose mothers had an initial digital cervical examination, but in none of the neonates in the early group, a difference that did not reach statistical significance (P = .061). Five (28%) of 18 infants from the delayed group whose mothers had received an initial digital cervical examination became infected, compared with none of the 78 infants from the delayed group whose mothers did not have digital examinations (P less than .001). We conclude that there is no advantage to delaying induction of labor when women present at term with spontaneous rupture of membranes.     

Ultrasonographic cervical length measurement is not a better predictor of preterm delivery than digital examination in a population of patients with idiopathic preterm labor

OBJECTIVE: To compare digital and ultrasonographic cervical examination for the prediction of preterm delivery in patients hospitalized for preterm labor. STUDY DESIGN: Fifty-nine patients were included. The Bishop score was evaluated upon admission, weeks gestational age. Ultrasonographic measurement of cervical length was done within 24h after entry. Delivery before 37 weeks gestational age was the primary endpoint. Attending obstetricians were blinded to the results of echography. RESULTS: Preterm delivery rate was 39% (23/59). The risk of preterm delivery was significantly increased when the Bishop score was greater than or equal to 6 (OR = 4.45 [1.41-14.01]) or when ultrasonographic cervical length was less than or equal to 27 mm (OR = 4.04 [1.32-12.3]), but digital examination was the only independent risk factor in multivariate analysis. Sensitivity, specificity, positive and negative predictive value for digital examination and ultrasonography were respectively 74, 61, 55 and 79%, 70, 64, 55 and 77%. Combination of digital examination and ultrasonography did not yield better results. CONCLUSION: In our series, prediction of preterm delivery was not improved by ultrasonography compared to digital examination. The size of the cervical shift observed in most patients hospitalized for preterm labor may render ultrasonography less relevant in identifying patients anticipated to deliver prematurely.     

Preinduction cervical ripening: basis and methods of current practice

The rate of women undergoing labor induction is increasing, primarily because of patient-physician preferences. The widespread availability of preinduction cervical ripening agents has contributed to this rising trend. Approximately half of all women undergoing an induction of labor will have an unfavorable cervix that will require some ripening agent. Pharmacologic and mechanical dilator techniques have been proven to ripen the unfavorable cervix. A topically applied prostaglandin product, containing either dinoprostone or misoprostol, is the most popular means to soften and dilate the cervix. Any uterine hyperstimulation may be reversed by administering a tocolytic drug and, if possible, by removal of the ripening agent. A minimum trial of adequate labor is necessary before considering the induction to be a failure. Cesarean delivery rates may be higher and the length of hospital stay more prolonged. Careful consideration about the need for labor induction is recommended until prospective clinical trials can better validate marginal reasons for cervical ripening.     

Management of prolonged pregnancy: induction of labor versus antepartum fetal testing

Three hundred two low-risk obstetric patients with an unfavorable cervical examination and well-established gestational age of at least 287 days were randomly selected for management by either antepartum fetal testing or prostaglandin gel cervical ripening followed by aggressive induction of labor and delivery. The patients managed by induction of labor had a lower incidence of meconium-stained amniotic fluid, meconium aspiration, low Apgar scores, postmaturity syndrome, fetal distress, and cesarean delivery than did patients managed with antepartum fetal testing. Our data suggest that prostaglandin gel cervical ripening and induction of labor and delivery by 42 weeks' gestation may be the most appropriate management for patients with well-established gestational age and an unfavorable cervical examination.     

Induction of labor

The rate of labor induction continues to rise significantly in the United States because of a growing use of labor induction for postterm pregnancies and elective induction of labor. Although different types and doses of prostaglandins used for cervical ripening often initiate uterine activity, the principal role of these agents is to soften the unripe cervix independent of uterine activity. Several systematic reviews with meta-analyses have shown that prostaglandins are superior to placebo and oxytocin alone in ripening of the cervix. Numerous studies and meta-analyses have assessed misoprostol's efficacy and safety as a labor induction agent. The most appropriate dose and route of administration has not yet been confirmed.     

Comparison of ultrasonographic and digital cervical evaluation

Findings on ultrasound scanning of the cervix and lower uterine segment were compared with those on digital examination in patients in preterm labor or those in whom induction was planned. An ultrasound scoring system gave results that corresponded closely to those of the Bishop score.     

Use of fetal fibronectin in women at risk for preterm delivery

Fetal fibronectin, a large molecular weight glycoprotein produced in the chorion, is expressed in cervical and vaginal secretions in women with disruption of the choriodecidual [table: see text] junction by labor or by inflammation. The presence of FFN in vaginal or cervical secretions before 35 weeks is a moderately good predictor of preterm delivery. The absence of FFN is a strong predictor that preterm delivery is unlikely within the next 7 to 14 days, with NPVs exceeding 99% in some studies. The predictive power of FFN is stronger at earlier gestation ages (24-28 wks) than it is later [table: see text] in pregnancy and is stronger for short-term prediction (7-14 d) than for predicting overall outcome (however, it remains statistically significant for predicting delivery < 37 wks). Although use of FFN in the clinical setting may require some changes to common protocols (e.g., performing sterile speculum examination before digital cervical examination), the use of FFN in patients with suspected preterm labor appears to have significant utility in reducing unnecessary interventions in women with symptoms suggestive of preterm labor. In women without symptoms, the use of FFN may be most beneficial in providing reassurance to some women thought to be at high-risk for preterm delivery because of past obstetric history. Screening women without symptoms at low-risk with FFN is not yet recommended because effective interventions are not demonstrated for patients found to be positive.     

应用会阴B超检测宫颈成熟度预测前列腺素E2引产效果的价值

目的评价会阴Ｂ超检测宫颈成熟度对预测前列腺素Ｅ２凝胶引产效果的价值。方法用会阴Ｂ超和指检法检测１０５例初产妇宫颈的成熟状况,记录引产潜伏期（引产至临产的时间）,并进行Ｃｏｘ模型多因素分析。结果会阴Ｂ超检查简单直观,较少引起孕妇不适感;宫颈长度、内口开大程度和先露高低是引产潜伏期的影响因素（Ｐ＜０．０５）;Ｂ超评分≥－４５的孕妇易在１２小时内临产（Ｐ＜０．００１）;预测结果与观察实际结果一致性很好,误诊较少（Ｋａｐｐａ值、特异性和阳性预测值依次为０．７４０９、０．７９１７、０．９２５４）,均优于Ｂｉｓｈｏｐ评分（相应结果为０．５６８０、０．６６６７、０８８０６）。结论会阴Ｂ超安全有效,其宫颈成熟度评分预测前列腺素Ｅ２凝胶引产难易程度效果较好。     

Use of uterine electromyography to diagnose term and preterm labor

Current methodologies to assess the process of labor, such as tocodynamometry or intrauterine pressure catheters, fetal fibronectin, cervical length measurement and digital cervical examination, have several major drawbacks. They only measure the onset of labor indirectly and do not detect cellular changes characteristic of true labor. Consequently, their predictive values for term or preterm delivery are poor. Uterine contractions are a result of the electrical activity within the myometrium. Measurement of uterine electromyography (EMG) has been shown to detect contractions as accurately as the currently used methods. In addition, changes in cell excitability and coupling required for effective contractions that lead to delivery are reflected in changes of several EMG parameters. Use of uterine EMG can help to identify patients in true labor better than any other method presently employed in the clinic.     

足月妊娠促宫颈成熟方法的探讨

目的:评价目前常用的足月妊娠促宫颈成熟方法的效果,为足月妊娠促宫颈成熟和引产提供有效、安全、方便的方法。方法:选择有引产指征的足月妊娠产妇221例,随机分为水囊组(A)80例,缩宫素组(B)45例,米索前列醇组(C)46例,普贝生组(D)50例,比较4组产妇的宫颈评分、分娩结局、新生儿结局和副作用。结果:水囊组促宫颈成熟效果最好,显著高于其他各组(P<0.05),剖宫产率低于其他各组(P<0.05)。普贝生组用药至临产时间及总产程明显短于其他各组(P<0.05)。各组新生儿窒息发生率和羊水污染率无显著差异。普贝生组发生子宫过度刺激症状者较多。结论:低位水囊有显著的促宫颈成熟的作用,配伍缩宫素在足月妊娠促宫颈成熟和引产过程中有效,普贝生促宫颈成熟安全有效,可选择性地用于有一定经济条件的孕妇。     

Prostaglandin E2 gel for cervical ripening and induction of labor: a critical analysis

This report summarizes the cumulative experience of 3313 pregnancies represented in 59 prospective clinical trials in which intracervical or intravaginal prostaglandin E2 gel was used for cervical ripening before induction of labor. Results indicate that local prostaglandin E2 is superior to placebo or no therapy in enhancing cervical effacement and dilation, reducing initial induction failures, shortening the induction-delivery interval, reducing oxytocin use, and lowering the rate of cesarean section because of failure to progress. Certain advantages also exist for labor induction in the presence of a favorable cervical state. Uterine hyperstimulation or pathologic fetal heart rate patterns before oxytocin administration occur in less than 1% of reported cases and are usually dose related, self contained, and reversible with the use of beta-adrenergic tocolytic therapy. Maternal systemic effects in these low doses are negligible. Worldwide clinical experience has clearly demonstrated that prostaglandin E2 gel administered before induction of labor is of major therapeutic benefit and should become commercially available for more than investigational use.     

普贝生配合缩宫素在足月妊娠引产中的临床应用

目的探讨普贝生配合缩宫素用于足月妊娠引产的临床效果及安全性。方法将120例妊娠足月、有引产指征的初产妇随机分为两组,研究组80例以普贝生并酌情配合缩宫素引产,对照组40例以缩宫素引产,比较两组产妇用药前后的宫颈Bishop评分、临产情况、剖宫产率、对母婴的影响。结果研究组促宫颈成熟有效率93.75%,高于对照组（40.00%）,用药至临产时间（12.51±10.73）h,短于对照组（21.12±15.10）h,引产成功率高（97.50%）,剖宫产率低（32.50%）。结论普贝生配合缩宫素可有效、安全地用于足月妊娠引产。     

Cervical ripening. A review and recommendations for clinical practice.

Cervical ripening occurs before the onset of labor. The cervix is metabolically active during ripening and passive during active labor. A ripe cervix indicates readiness for labor and predicts successful induction of labor. Practitioners evaluate cervical readiness for labor using the Bishop score. Membrane stripping, mechanical dilators and prostaglandins are ripening methods used frequently because they are simple, effective, efficient, safe and well tolerated. Stripping of membranes, a Foley catheter and misoprostol tablets are less expensive than other available methods. Because prostaglandins may cause excessive myometrial activity and even labor, hospitalization and fetal monitoring are recommended. Despite their effectiveness, these methods often do not decrease the cesarean section rates. This finding may be explained by the fact that each study reviewed only included a small number of patients and that in most cases, amniotomy was done and induction started, when feasible, before the women reached a Bishop score > or = 9. Larger studies may have different outcomes. The type of ripening methods used depends on the urgency of the situation; balloon catheters and prostglandins often act within 12 hours, while membrane stripping is less predictable.     

Assessment of cervical dilatation during labor: a review

Various techniques for assessment of cervical dilatation during labor or 'cervimetry' have been described, including digital, (electro)mechanical, electromagnetic and ultrasound cervimetry. In this paper the validity and usefulness of instrumental cervimetry is assessed on the basis of the available literature. Cervimetry using ultrasound transducers allows continuous and reliable recording of cervical dilatation during labor with little discomfort to the patient. In comparison with other instrumental techniques for measurement of cervical dilation ultrasound cervimetry seems to be the most promising method available.     

Quantification of cervical change: relationship to preterm delivery in the multifetal gestation.

Prematurity is the major contributor to the very high perinatal morbidity and mortality associated with multifetal gestations. Antepartum cervical evaluation has been suggested as a way to better define the risk of preterm delivery in multifetal gestations. Weekly digital cervical examinations were performed in 86 twin and 7 triplet gestations that were being monitored in a special antepartum clinic. A cervical score was calculated from each examination by subtracting cervical dilatation in centimeters from cervical length in centimeters. Cervical scores decline gradually with advancing gestation and are influenced by parity and subsequent preterm delivery. Intervals until delivery decrease significantly with lower cervical scores. A cervical score less than or equal to 0 on or before 34 weeks' gestation was strongly predictive of preterm delivery (75%). Only 2 of 78 (2.6%) with a score greater than 0 were delivered within 1 week of the examination. Cervical scoring is a simple, quantifiable, reproducible, and safe method of evaluating preterm delivery risk. An understanding of the prognostic significance of specific cervical scores may be of value in determining the need for obstetric intervention.