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.     

Cervical ripening with intravaginal prostaglandin E2 gel

Ripening of the cervix by intravaginal application of a prostaglandin-containing gel is evaluated. Thirty patients with an unfavorable cervix needing labor induction were studied in a double-blind, prospective fashion. The prostaglandin gel proved superior to placebo in ripening the cervix (P less than .05), reducing induction failures (P less than .025), diminishing the oxytocin dosage necessary for induction (P less than .05), and lowering the rate of cesarean section (.05 less than P less than .1). One hundred fifty additional patients with varying Bishop scores and differing clinical situations were also studied. There were 35 cesarean sections (23.3%), nine failed inductions (6%), a spontaneous labor rate of 46%, and an average Bishop score change of 2.5. Twenty patients with premature rupture of the membranes and an unfavorable cervix received a modified gel containing 2.5 mg of prostaglandin E2. Average Bishop score change was 2.9, and there was a 55% incidence of spontaneous labor.     

Transvaginal ultrasonography of the uterine cervix before induction of labor]

OBJECTIVE: To compare the Bishop score and transvaginal ultrasonographic measurement of cervical length for predicting the mode of delivery following medically indicated induction of labor in term patients. METHOD: The study was conducted prospectively among 134 women who required medically indicated induction of labor. Inclusion criteria were singleton pregnancy, gestational age > or = 37 weeks of amenorrhea, cephalic presentation, and intact fetal membranes. Transvaginal ultrasonography was performed for measurement of the cervical length but the patients were managed without considering this parameter. A receiver-operating characteristic curve was constructed to determine the best cut-of value of cervical length for predicting the risk of cesarean section following induction of labor. RESULTS: Thirty six patients (26.9%) underwent cesarean section and cervical dilatation at time of the cesarean section was < 8 cm in 25 cases. The Bishop score was not predictive for the mode of delivery in this study. In contrast, the cesarean section rate was significantly lower in women with a uterine cervix < 26 mm (18.9 vs 36.6%, p = 0.02). Moreover, the difference has concerned only the cesarean sections performed before 8 cm dilatation (9.5 vs 30.0%, p = 0.002). CONCLUSION: Cervical length measured with transvaginal ultrasonography is a better predictor than the Bishop score for predicting the risk of cesarean section following medically indicated induction of labor.     

Management of term patients with premature rupture of membranes and an unfavorable cervix.

The purpose of this prospective investigation was to evaluate a protocol for management of term patients with premature rupture of membranes (PROM) and a cervix unfavorable for induction of labor (Bishop score 4 or less). Patients initially were observed for 24 to 36 hours for the spontaneous onset of labor. If spontaneous contractions did not commence, labor was induced with oxytocin. Patients subsequently were divided into three groups: 44 who had spontaneous labor, 29 who had spontaneous labor but required oxytocin augmentation, and 39 women who had oxytocin induction. Patients who entered labor spontaneously had a significantly shorter mean latent period between rupture of membranes and onset of labor (16.0 versus 26.8 and 40.7 hours), shorter mean duration of labor (7.6 versus 12.1 and 13.1 hours), and shorter mean duration of rupture of membranes (23.6 versus 39.0 and 53.8 hours). These women also had a significant decrease in the frequency of chorioamnionitis (7 versus 14 and 33%), and their infants had fewer evaluations for sepsis (25.0 versus 34.5 and 53.8%). We conclude that term patients with PROM and an unfavorable cervix who require oxytocin augmentation or induction of labor are at increased risk for intrapartum and neonatal infection compared with those who progress through labor spontaneously.     

Effect of vaginal pH on efficacy of misoprostol for cervical ripening and labor induction

OBJECTIVE: We sought to evaluate whether vaginal pH has an effect on the relative efficacy of misoprostol for cervical ripening and labor induction. STUDY DESIGN: Thirty-seven gravid women with an unfavorable cervix and indication for labor induction were enrolled in this prospective, double-blind, observational study. Baseline assessments of cervicovaginal pH and Bishop score were made at the time of enrollment by an independent examiner. All patients received 50 microg misoprostol intravaginally every 6 hours for 12 hours. After the initial 12 hours of preinduction, a repeat Bishop score assessment was made by the same initial examiner. Patients not in active labor at 12 hours were placed on a standardized oxytocin induction regimen. Labor was managed by the on-call obstetric team, who remained blinded to pH assessment. Clinical outcomes were evaluated. Statistical analyses were made by the Student t test, the Fisher exact test, and linear regression analysis. RESULTS: Average initial vaginal pH was 4.8 +/- 0.5 (range, 3.5-7.0) for the study cohort. No significant differences were noted between those patients with low vaginal pH (< or =4.5) compared with those with high pH vaginal (>4.5) with respect to maternal age, parity, gestational age, or initial Bishop score. Similarly, Bishop score change over preinduction interval (5.6 vs 4.9), time to active labor (16.3 vs 17. 1 hours), time to complete dilatation (20.0 vs 19.9 hours), and time to delivery (21.0 vs 21.6 hours) were not significantly different between the low and high pH groups, respectively. Linear regression analysis revealed no significant association between vaginal pH and Bishop score change during preinduction interval, time to active labor, time to complete dilatation, or time to delivery. CONCLUSION: Vaginal pH does not appear to influence the efficacy of intravaginally administered misoprostol for cervical ripening and labor induction.     

Foley尿管水囊促宫颈成熟用于足月妊娠引产的前瞻性随机对照研究

目的 比较Foley尿管水囊与普贝生栓促宫颈成熟用于足月妊娠引产的安全性和有效性. 方法 采用前瞻性随机对照研究方法,选择2009年6月至12月在本院待产的孕足月、单胎头位、有引产指征、阴道清洁度≤Ⅱ度、胎膜完整、官颈Bishop评分＜6分的初产妇,签署随机对照研究知情同意书后,随机分为2组,最终纳入分析的共126例,分别予Foley尿管水囊(64例)和普贝生栓(62例)促官颈成熟,Foley尿管水囊组与普贝生栓组孕妇的孕周、引产前宫颈评分、引产指征差异无统计学意义.采用t、x2检验或Fisher精确概率法比较2组孕妇的引产成功率、分娩方式、产程时间及母儿结局. 结果 Foley尿管水囊组与普贝生栓组宫颈评分改善、引产成功率、阴道分娩率、总产程、产后出血量差异均无统计学意义(P＞0.05).Foley尿管水囊组较普贝生栓组引产24 h内阴道分娩率低[28.1％(18/64)与56.5％(35/62),t=10.37,P＜0.05],宫缩过频过强发生率也较低[0.0％(0/64)与17.7％(11/62),P＜0.05],但缩宫素使用率高[87.5％(56/64)与21.0％(13/62),x2 =56.27,P＜0.05].2组新生儿Apgar评分、羊水胎粪污染发生率、新生儿体重差异均无统计学意义(P＞0.05).2组孕妇无一例发生产褥感染. 结论 严格掌握Foley尿管水囊促宫颈成熟的指征及执行无菌操作规程,可以取得与普贝生栓相似的促官颈成熟效果及引产母婴结局,未发生过频过强官缩,具有安全性高及成本低廉等优点.     

Transvaginal ultrasonographic cervical measurement as a predictor of successful labor induction

OBJECTIVE: Our purpose was to compare transvaginal cervical measurement and the Bishop score as indicators of duration of labor and successful induction of labor at term.Study Design: This prospective observational study recruited women with singleton gestations scheduled for induction of labor at > or =37 weeks. Transvaginal ultrasonographic measurement of cervical length was performed and the Bishop score was determined, each by operators masked to the other measurement. Data were collected on parity, gestational age, mode of delivery, induction agent, induction-to-delivery interval, Bishop score, and cervical length measurement. RESULTS: A total of 77 women were analyzed. Vaginal delivery occurred in 69%. Both Bishop score and cervical length showed linear correlation with duration of labor (R(2) = 0.43, P <. 001; R(2) = 0.48, P <.001; respectively). Women with cervical length <3.0 cm had shorter labors (P <.001) and were more likely to be delivered vaginally (P <.001). Women with a Bishop score >4 also had shorter labors and were more likely to be delivered vaginally, with similar P values. A logistic regression model identified cervical length and parity as the only independent predictors of vaginal delivery. CONCLUSIONS: Both ultrasonographically measured cervical length and Bishop score predict duration of labor and likelihood of vaginal delivery. However, only cervical length and parity were independent predictors of mode of delivery.     

Intracervical misoprostol as an effective method of labor induction at term.

OBJECTS: The purpose of this study was to evaluate the safety and effectiveness of intracervical misoprostol for the induction of labor at term. METHODS: Eighty-nine term pregnancies requiring induction of labor were treated intracervically with 50 microg of misoprostol. The dose was repeated every 4 h until adequate uterine contraction and cervical dilatation were achieved. Status of cervical ripening, uterine contraction, cervical dilatation, labor course and side effects were recorded and analyzed. RESULTS: Among the 89 patients, 58 had an unfavorable cervix (Bishop score < or = 4) and 31 had a favorable cervix (Bishop score > 4). Labor was successfully induced in all cases, most (93.3%) of which required a single dose of misoprostol. Seventy-two patients (81%) proceeded to spontaneous vaginal delivery, and 61 (85%) deliveries were achieved within 12 h. The other 17 cases received cesarean delivery with indications of fetopelvic disproportion (six cases), failure of induction (seven cases) and acute fetal distress (four cases). The mean duration from induction to regular uterine contraction and to delivery was 483+/-537 min and 79.2+/-38.2 min, respectively, with no significant difference between the two groups with differing status of cervical ripening. Complications of uterine contraction, including tachysystole (15 cases), hypertonus (one case) and hyperstimulation (10 cases) were more common in the group of unfavorable cervix (45%) than that of favorable cervix (23%) (P < 0.05). CONCLUSION: In addition to the oral and intravaginal routes of administration, intracervical misoprostol at a single dose of 50 microg appears to be an effective method for induction of labor at term, but caution should be taken with cases with unfavorable cervix.     

Élastographie du col utérin : prédiction du délai d’accouchement lors d’un déclenchement par prostaglandines

ObjectiveInduction of labor for medical indications has become a routine practice. To date, the Bishop score remains as the standard method to predict the duration of induced labor. Elastography is an objective method of assessing the relative consistency of tissues. Therefore, we sought to assess strain elastography of cervix to predict delay from induction to delivery in pregnant women with a low Bishop score.Patients and methodsUltrasound elastography was immediately performed before induction of labor for medical indications among patients with a singleton pregnancy at > 36 weeks of gestation and a Bishop score < 6. Patients received 50 μg of misoprostol intravaginally, repeated 6 hours later if regular painful uterine contractions had not started. A second ultrasound elastography was also performed 6 hours after starting the induction before the second dose of misoprostol if regular painful uterine contractions had not started. At each examination, a color map from blue (hardest tissue) to red (softest tissue) was produced. The cervical elastography was considered as positive if at least one part of its anterior wall was red. We assessed the predictive value of elastography on vaginal delivery within 24 hours. Patients delivering by cesarean section were excluded from this study.ResultsElastography was initially performed in 48 patients. Twelve patients delivering by cesarean section after induction of labor were excluded, leading to 36 patients evaluated in this study. Among these 36 patients with elastography performed before induction of labor, 20 had a second elastography before the second dose of misoprostol. Sensibility, specificity, positive predictive value (PPV) and negative predictive value (NPV) of elastography performed before induction of labor on vaginal delivery within 24 hours were 40%, 27.3%, 55.6%, and 16.7%, respectively. Sensibility, specificity, PPV and NPV of elastography performed before the second dose of misoprostol were 64.3%, 16.7%, 64.3% and 16.7%, respectively. Among the 8 patients with red color occurring on the second cervical color map, sensibility, specificity, PPV and NPV were 83.3%, 0%, 62.5%, and 0%.Discussion and conclusionQualitative cervical elastography is a poor predictor for delay from induction to delivery in pregnant women with a low Bishop score.     

Factors affecting the likelihood of successful induction after intravaginal misoprostol application for cervical ripening and labor induction

OBJECTIVE: Our purpose was to determine whether maternal age, height and weight, parity, duration of pregnancy, cervical dilatation or Bishop score, and birth weight could be used to predict the likelihood of successful induction in women given intravaginal misoprostol. STUDY DESIGN: A computerized database was compiled of 1373 pregnancies in which intravaginal misoprostol was given for cervical ripening and labor induction. Most of these women were placed on investigational protocols in which the dose of misoprostol administered was 25 to 50 microg and the dosing intervals ranged from 3 to 6 hours. No more than 24 hours of administration was permitted. Induction was undertaken in women with unfavorable cervical examinations (Bishop scores of 4 or less) and without spontaneous labor or ruptured membranes. Univariate and stepwise multiple regression analyses were performed to identify those factors associated with successful induction, defined as vaginal delivery within 24 hours of induction. RESULTS: Six hundred fifty-seven (48%) had successful induction. Parity (odds ratio [OR] 2.5, 95% CI 2.0-2.9, P <.0001), initial cervical dilatation (OR 1.9, 95% CI 1.6-2.3, P <.0001), Bishop score (OR 1.6, 95% CI 1.3, 1.8, P <.0001), and gestational age at entry (OR 1.3, 95% CI 1.1-1.5, P =.002) were significant at the.05 level for predicting successful induction. A multivariate stepwise logistic regression was then performed to evaluate each of these as independent predictors. Parity (OR 2.4, 95% CI 2.0-3.0, P <.0001), initial cervical dilatation (OR 1.7, 95% CI 1.4-2.1, P <.0001), and estimated gestational age (OR 1.3, 95% CI 1.1-1.6, P =.003) are significant independent predictors for successful induction, but initial Bishop score is not significant (P =.19) after adjustment for other significant predicting factors. CONCLUSIONS: The clinical characteristics of parity, initial cervical dilatation, and gestational age at entry are predictors of the likelihood of success of cervical ripening and labor induction with intravaginal misoprostol administration.     

Failed induction of labor despite sequential prostaglandin E2 therapy

Preinduction cervical ripening with prostaglandin E2 (PGE2) is useful in minimizing the chances for a failed induction of labor. The lack of sufficient cervical dilation despite PGE2 and oxytocin therapy is uncommon. This investigation was undertaken to determine reasons for any failed inductions in pregnancies with pregel Bishop scores 4 or lower and requiring delivery within 24 hours. Fifteen (12.1%) of 124 eligible patients had failed inductions despite two 2.5 mg intravaginal doses. A finding in all the failures was a very unfavorable cervix (pregel Bishop score 0 to 2). The need for preterm delivery (33 to 37 weeks) was a common finding in the presence of a very unfavorable cervix. The data suggest that complicated pregnancies requiring delivery within 24 hours and failing to respond to sequential PGE2 therapy in the presence of a very unfavorable cervix may benefit from cesarean section without a prolonged induction.     

Predictive value of pelvic scores for induction of labor by local PGE2.

The predictive value of pelvic scores, parity, age and gestational age for induction of labor by local prostaglandin-E2 (PGE2) was examined in 336 women attempting induction of labor by intracervical or vaginal PGE2. The patient characteristics were correlated to: (1) vaginal delivery within 48 h, (2) the period from induction to onset of labor (latency period), and (3) the duration of labor. The Bishop score (P < 0.01) and even more the Lange score (P < 0.0001) were significantly inversely correlated to both latency period and induction-delivery period. This was caused by cervical dilatation (P < 0.001), fetal station (P < 0.05) and cervical length (P < 0.05), whereas position and consistency of the cervix were of no importance. All three periods studied were significantly (P < 0.0001) shorter in parous women. In primiparous women, gestational age was of no importance for the latency period; however, higher gestational age was associated with longer labor (P < 0.001). We conclude that the predictive value of pelvic scores on induction hardly differs using local PGE2 compared to conventional methods; furthermore, the Bishop score should be substituted, disregarding position and consistency of the cervix, but putting more weight to cervical dilatation. A new pelvic score is proposed.     

应用胎儿纤连蛋白选择足月妊娠引产时机

目的探讨宫颈阴道分泌物胎儿纤连蛋白(fFN)定性测定能否指导足月妊娠引产时机的选择.方法64例初产、足月、头位、单胎、未破膜、未临产、3日内无同房史、无严重妊娠合并症、并发症,在引产开始前行宫颈阴道分泌物fFN定性测定,然后肛诊作宫颈Bishop评分,选用缩宫素引产.另有11例符合上述条件的孕妇,在引产过程中作fFN测定.结果fFN预示引产成功的敏感度61.7%,特异度70.59%,阳性预示率85.29%,阴性预示率40.00%,均优于宫颈Bishop评分.fFN(+)组引产成功的时间短于阴性组,引产次数也较阴性组少.当fFN(+)、宫颈触诊软时,90.9%在3天内引产成功;fFN(+)宫颈不软或fFN(-)、宫颈软时,引产成功率降为80%左右;fFN(-)、宫颈不软时,引产的成功率仅为44%.在引产过程中测定fFN,其结果与引产效果基本相符(8/11).结论fFN是反映宫颈成熟度的良好标志,较宫颈Bishop评分更正确、客观.定性测定宫颈阴道分泌物fFN可用于指导足月妊娠引产时机的选择,将fFN与Bishop评分,尤其宫颈的软硬度结合考虑将提高正确性.     

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.     

Role of prostaglandin-induced cervical changes in labor induction

The role of the cervix in labor induction has been studied in a previous report. Cervical preparation by mechanical methods did not alter the course of induced labor. The same hypothesis is further elucidated in the present study using prostaglandin E2 vaginal suppositories for cervical preparation. Forty-seven pregnant women near term with Bishop scores of 4 or less were divided into three study groups: control subjects, oxytocin-treated patients, and prostaglandin group. A 12-hour preparation phase procedure was carried out to produce cervical and/or myometrial changes. All women had continuous measurement of uterine activity by an extraovular catheter. At the end of the preparation phase, the Bishop score was reevaluated, amniotomy carried out in all patients, and oxytocin infusion either started or continued. Although prostaglandin and oxytocin both significantly changed the cervix, oxytocin had the shortest induction-to-delivery interval, though the prostaglandin-treated group required lower concentrations of oxytocin. The authors conclude that with rigid control of Bishop score and timing of amniotomy and oxytocin infusion rates, prostaglandin-induced cervical changes alone did not uniquely benefit labor induction in the doses used, or within the time frame of the study.     

Preinduction cervical assessment

The rate of labor induction is increasing in the United States. Methods for quantifying cervical factors have been developed to identify patients who may benefit from cervical ripening before induction. The first cervical scoring systems used digital examination. More recently, cervical ultrasound and testing for the presence of fetal fibronectin have been suggested to evaluate cervical readiness for labor induction, but neither of these methods provides a significant improvement over digital examination. The Bishop score, the most widely used digital examination scoring system, still is the most cost effective and accurate method of evaluating the cervix before labor induction.     

Electrical impedance measurements: an objective measure of prelabor cervical change.

OBJECTIVE: To investigate the use of electrical impedance measurements of the pregnant cervix as an objective measure of cervical favorability (Bishop score > or = 5). METHODS: A prospective study of 86 women, investigating electrical impedance measurements of the pregnant cervix at the time of induction of labor. Transfer electrical impedance measurements were made by placing a tetrapolar pencil probe of 8 mm in diameter on the surface of the cervix. A Bishop score was determined simultaneously. RESULTS: A mean resistivity (standard error of the mean) of 7.03 (6.01-8.04) omega(m) was measured for the unfavorable group and 5.34 (4.61-6.07) omega(m) for the favorable group. This was a statistically significant difference (p = 0.016). CONCLUSION: We highlight the ability of this safe, painless technique to differentiate the favorable from the unfavorable cervix at induction of labor.     

Sonographic cervical length measurement before labor induction in term nulliparous women

OBJECTIVE: The purpose of the study was to determine if transvaginal sonographic measurement of the cervical length is a useful method to predict successful labor induction in nulliparas. METHODS: 137 women who were scheduled for medically indicated induction of labor had a transvaginal sonographic measurement of the cervical length before labor induction. Inclusion criteria were: (1) singleton pregnancy; (2) gestational age between 37-42 weeks; (3) live fetus in cephalic presentation; (4) intact membranes; (5) no vaginal bleeding; (6) no previous history of uterine surgery; (7) nulliparous women, and (8) no allergy or asthma in response to prostaglandins. Induction of labor was performed within 6 h of the ultrasonographic examination, by inserting 2 mg of dinoprostone in the posterior vaginal fornix, repeated if needed every 6 h for up to three doses. When the cervix became favorable and no regular contractions were observed, amniotomy and oxytocin augmentation, starting at 1 mIU/min and increasing 1 mIU every 30 min as necessary, was performed. RESULTS: All women were Caucasians and the mean age was 24.3 years (range 19-37 years). The mean cervical length was 28 mm (range 11-39 mm). The Bishop score was < or =5 in 101 women and >5 in the 36 others. Vaginal delivery occurred in 92 women (67.1%), and the vast majority of them (89 women; 96.7%) gave birth within 24 h of induction. Forty-five women (32.8%) had a cesarean section. The Bishop score was not predictive of the mode of delivery. Thirty-six of 101 women (35.6%) with a Bishop score < or =5 delivered by cesarean section, compared to 9 of 36 women with a Bishop score >5 (25%) (p = NS). Women with a cervical length <27 mm were more likely to deliver vaginally. Using this cutoff value the sensitivity of a successful labor induction was 76% and the specificity was 75.5%. CONCLUSIONS: Transvaginal sonographic measurement of cervical length is a good predictor of a successful labor induction at term in nulliparas.     

Comparison of pre-induction ultrasonographic cervical length and Bishop score in predicting risk of cesarean section after labor induction with prostaglandins

OBJECTIVE: To compare pre-induction ultrasonographic cervical length and Bishop score in predicting risk of caesarean section after labor induction with prostaglandins. PATIENTS AND METHODS: Assessment of the Bishop score and measurement of the cervical length by transvaginal sonography were performed by two operators, blinded to each other's results among women with singleton pregnancies at between 34(+0) - 41(+3) weeks of gestation requiring induction of labor with prostaglandins for medical indications. Fisher's exact test and regression logistic models were used for statistics analysis. In order to measure the strength of the association between ultrasonographic cervical length or Bishop score on one hand, and the caesarean sections rate (global or for failed induction or failure to progress) on the other hand, we computed odds ratios with 95% confidence interval. RESULTS: Among the 266 patients included in the study, multivariate analysis has shown that only Bishop score was predictive for the global caesarean section risk (OR [95% CI] 0.63 [0.45-0.87] ; P =0.005). However, neither Bishop score (OR [95% CI] 0.68 [0.42-1.09] ; P =0.11), nor ultrasonographic cervical length (OR [95% CI] 1.01 [0.95-1.08] ; P =0.59) was predictive for failed induction or failure to progress caesarean section risk. DISCUSSION AND CONCLUSION: The Bishop score appears to be a better predictor of the global caesarean section risk than ultrasonographic cervical length after induction of labor for medical reasons.     

Digital and transvaginal ultrasound cervical assessment for prediction of successful labor induction.

OBJECTIVE: To compare the values of preinduction transvaginal cervical length measurements and Bishop score to predict successful labor induction. METHODS: A prospective, observational trial of nulliparous women undergoing labor induction. Inclusion criteria were gestational age between 36 and 42 weeks, singleton cephalic presentation of the fetus, and intact membranes. Preinduction cervical ripening was performed using 25 microg intravaginal misoprostol (PGE1), repeated every 4 h, up to a maximum of 3 doses. Induction was subsequently continued by oxytocin and amniotomy. RESULTS: A total of 43 women met the inclusion criteria. Mean preinduction cervical length for women with successful or failed labor induction was 26 mm (95% Confidence interval [CI], 27-32) and 34 mm (95% CI, 33-38), respectively (P=0.002). Mean Bishop scores for successful and failed induction groups were 5.4 (95% CI, 5.2-6.2) and 3.1 (95% CI, 2.8-3.5), respectively (P=0.003). CONCLUSION: Digital examination and transvaginal ultrasound of the cervix predict successful labor induction with reasonable accuracy.