Bishop score and risk of cesarean delivery after induction of labor in nulliparous women

OBJECTIVE: To quantify the risk and risk factors for cesarean delivery associated with medical and elective induction of labor in nulliparous women. METHODS: A prospective cohort study was performed in nulliparous women at term with vertex singleton gestations who had labor induced at 2 obstetrical centers. Medical and elective indications and Bishop scores were recorded before labor induction. Obstetric and neonatal data were analyzed and compared with the results in women with a spontaneous onset of labor. Data were analyzed using univariate and multivariable regression modeling. RESULTS: A total of 1,389 women were included in the study. The cesarean delivery rate was 12.0% in women with a spontaneous onset of labor (n = 765), 23.4% in women undergoing labor induction for medical reasons (n = 435) (unadjusted odds ratio [OR] 2.24; 95% confidence interval [CI] 1.64-3.06), and 23.8% in women whose labor was electively induced (n = 189) (unadjusted OR 2.29; 95% CI 1.53-3.41). However, after adjusting for the Bishop score at admission, no significant differences in cesarean delivery rates were found among the 3 groups. A Bishop score of 5 or less was a predominant risk factor for a cesarean delivery in all 3 groups (adjusted OR 2.32; 95% CI 1.66-3.25). Other variables with significantly increased risk for cesarean delivery included maternal age of 30 years or older, body mass index of 31 or higher, use of epidural analgesia during the first stage of labor, and birth weight of 3,500 g or higher. In both induction groups, more newborns required neonatal care, more mothers needed a blood transfusion, and the maternal hospital stay was longer. CONCLUSION: Compared with spontaneous onset of labor, medical and elective induction of labor in nulliparous women at term with a single fetus in cephalic presentation is associated with an increased risk of cesarean delivery, predominantly related to an unfavorable Bishop score at admission. LEVEL OF EVIDENCE: II-2.     

The labor induction: integrated clinical and sonographic variables that predict the outcome.

OBJECTIVE: To analyze the clinical and sonographic variables that predicts the success of labor induction. STUDY DESIGN: We studied the Bishop score, cervical length and parity in 196 pregnant women in the prediction of successful vaginal delivery within 24 h of induction. Logistic regression and segmentation analysis were performed. RESULTS: Cervical length (odds ratio (OR) 1.089, P<0.001), Bishop score (OR 0.751, P=0.001) and parity (OR 4.7, P<0.001) predict the success of labor induction. In a global analysis of the variables studied, the best statistic sequence that predicts the labor induction was found when we introduced parity in the first place. The success of labor induction in nulliparous was 50.8 and 83.3% in multiparous women (P=0.0001). CONCLUSIONS: Cervical length, Bishop score and parity, integrated in a flow chart, provide independent prediction of vaginal delivery within 24 h of induction.     

When has an induction failed?

OBJECTIVE: To evaluate the length of the latent phase that, during labor inductions in nulliparous women, is associated with significantly decreased chance of vaginal delivery and increased risk of maternal and neonatal morbidity. METHODS: All inductions of labor during a 6-month period were identified. Only those women who were nulliparous with a pregnancy of 36 weeks or more of gestation underwent further data analysis. Demographic data, intrapartum course, and maternal and neonatal outcomes were abstracted from the medical record. The latent phase was defined as beginning after oxytocin had been initiated and amniotomy performed and continuing until either 4 cm cervical dilation and 80% effacement or 5 cm cervical dilation regardless of effacement. RESULTS: A total of 397 nulliparous women, 32% of whom underwent cervical ripening, presented during the study period. Only 8 women (2%) never achieved active phase labor before cesarean, and the overall cesarean rate was 26.0%. A longer latent phase was associated with a greater rate of cesarean delivery, although only after 18 hours did a majority of induced labors result in cesarean. Chorioamnionitis and postpartum hemorrhage were more frequent with latent phases of labor greater than 18 hours (16% and 26%, respectively), although these diagnoses did not translate into greater risk of transfusion, hysterectomy, or prolonged hospitalization. Neonatal outcomes, including meconium passage, fetal acidemia, neonatal intensive care unit admission, or other morbidity did not increase in conjunction with longer latent phases. CONCLUSION: A latent phase of as long as 18 hours during induction of labor in nulliparous women allows the majority of these women to achieve a vaginal delivery without being subject to a significantly increased risk of significant maternal or neonatal morbidity. LEVEL OF EVIDENCE: II-2.     

Variables that predict the success of labor induction

BACKGROUND. To analyze the clinical and sonographic variables that affect the success of labor induction. METHODS. Bishop score, cervical length, and parity were studied in 196 pregnant women in the prediction of successful vaginal delivery within 24 hr of induction. Logistic regression and segmentation analysis were performed. RESULTS. Cervical length [odds ratio (OR) 1.089, P<0.001], Bishop score (OR 0.751, P=0.001), and parity (OR 6.85, P<0.001) predict the success of labor induction. The best cut-off points for cervical length were <16.5, 16.5--27, and >27 mm (P=0.0016). In the analysis of the Bishop score, we also obtained three discriminatory points, 0, 1--4, and >4 (P=0.0006), that best predict the labor induction. Finally, in a global analysis of the variables studied, the best statistic sequence that predicts the labor induction was found when we introduced parity in the first place. The success of labor induction in nulliparous was 50.77 and 83.33% in multiparous (P=0.0001). CONCLUSIONS. Cervical length, Bishop score, and parity predict the success of labor induction.     

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.     

Comparison of digital and ultrasonographic examination of the cervix in predicting time interval from induction to delivery in women with a low Bishop score

OBJECTIVE: To compare pre-induction ultrasonographic cervical length and Bishop score in predicting time to delivery after labour induction with prostaglandins. DESIGN: Prognostic cohort study. SETTING: Tertiary referral maternity unit in a teaching hospital. POPULATION: Two hundred and sixty-six women with singleton pregnancies at between 34(+0) and 41(+3) weeks of gestation requiring induction of labour with prostaglandins for medical indications. METHODS: A secondary analysis of a trial comparing two prostaglandins. 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. We estimated the predictive effects on the outcomes of ultrasonographic cervical length and Bishop score. MAIN OUTCOME MEASURE: Time intervals from induction to delivery and to vaginal delivery. RESULTS: Cervical length and Bishop score were associated with the time interval from induction to delivery, based on univariable analyses. When considered jointly in a multivariable model, only the Bishop score was significantly related to the outcome: The higher the Bishop score, the higher the hazard to delivery [hazard ratio (HR): 1.2, 95% confidence interval (CI): 1.1-1.3], illustrating that once the Bishop score is taken into account, further knowledge of cervical ultrasound length (HR: 0.99, 95% CI: 0.98-1.0) did not add any predictive information. Also, Bishop score was predictive of time interval between induction and vaginal delivery (HR: 1.2, 95% CI: 1.1-1.4) while cervical length had no additional predictive value (HR: 0.99, 95% CI: 0.98-1.0) when both cervical length and Bishop score were introduced in the model. CONCLUSIONS: The Bishop score appears to be a better predictor of the time interval from induction to delivery and to vaginal delivery than cervical length after induction of labour for medical reasons.     

Graphic analysis of actively managed labor: prospective computation of labor progress in 500 consecutive nulliparous women in spontaneous labor at term

OBJECTIVE: Active management has been shown to shorten the length of labor and reduce the incidence of prolonged labor. We examined the influence of this protocol on the rate of cervical dilatation by calculating a mean partogram to explain how this acceleration is achieved. STUDY DESIGN: We retrospectively analyzed partograms of cervical dilation in 500 consecutive nulliparous women in spontaneous labor at term with a singleton fetus in a cephalic presentation; cesarean deliveries were not excluded. Mean cervical dilations at admission and mean time intervals to reach 2, 3, 4, 6, 8, and 10 cm of dilatation and delivery were calculated, with 95% confidence intervals, both for the whole cohort and specifically in women with cervical dilatations <3 cm at admission. These data were used to construct mean partograms. RESULTS: The mean duration of labor was 6.1 hours. The mean cervical dilatation at admission was 1. 7 cm; all but 2.8% were delivered within 12 hours. The cesarean rate was 5.4%. The mean partogram, with narrow 95% confidence intervals, shows a rapid active phase after a much shorter latent phase than reported in other analyses of labor. CONCLUSION: Active management reduces the duration of first labor mainly by shortening the latent phase in association with amniotomy at very early cervical dilatations and does not delay the diagnosis of labor until the active phase has begun.     

Ultrasound and clinical predictors for Caesarean delivery after labour induction at term

OBJECTIVE: To assess the relationship of ultrasound assessment for amniotic fluid, fetal weight, cervical length, cervical funneling and clinical factors on the risk of Caesarean delivery after labour induction at term. METHODS: On hundred and fifty-two women scheduled for labour induction at term agreed to participate. Sonography was performed to obtain fetal biometry, amniotic fluid index and cervical length and to detect funneling at the internal cervical os. The sonographic findings were concealed. Study women received standard care during labour induction. RESULTS: On univariate analysis using Fisher's exact test, parity, cervical length and Bishop score were associated with Caesarean delivery. Following multivariable logistic regression analysis, only nulliparity (adjusted odds ratio (AOR) 5.2 (95% CI 2.2-12.2): P<0.001) and transvaginal ultrasound-determined cervical length of more than 20 mm (AOR 2.8 (95% CI 1.0-7.4): P=0.04) were independent predictors of Caesarean delivery in labour induction. Maternal age, maternal height, gestational age, indication for labour induction, amniotic fluid index, cervical funneling and ultrasound-estimated fetal weight did not predict Caesarean delivery. CONCLUSION: In women who had undergone labour induction at term with a singleton fetus, nulliparity and cervical length of more than 20 mm on transvaginal sonography were independent predictors of Caesarean delivery. This information is helpful for pre-induction counselling.     

Pre-induction sonographic assessment of the cervix in the prediction of successful induction of labour in nulliparous women

OBJECTIVE: To compare the efficacy of ultrasonographic cervical assessment with Bishop score before induction of labour in predicting the success of labour induction in nulliparous women. METHODS: This is a prospective study conducted in 138 women who underwent cervical assessment with transvaginal sonography followed by digital cervical assessment using Bishop score before induction of labour. Ultrasonographic parameters evaluated were cervical length, posterior cervical angle and funnelling were blinded to the managing physicians. Statistical analysis was carried out using Mann-Whitney test, chi2 test, receiver operating characteristics curves and logistic regression analysis. RESULTS: Induction of labour was successful in 106 (76.8%) of the women. Multiple logistic regression analysis demonstrated cervical length and posterior cervical angle assessed by transvaginal sonography as independent predictors of successful outcome after induction of labour. Neither Bishop score nor its individual parameters were found to be significant in the regression analysis. The area under the receiver operating characteristic curve for cervical length and posterior cervical angle was greater than that of the Bishop score in predicting a successful labour induction. The best cut-off point for the parameters in receiver operating characteristics curve was 3.0 cm for cervical length and 100 degrees for posterior cervical angle. Cervical length of 3.0 cm had a sensitivity of 84.9%, and a specificity of 90.6% and a posterior cervical angle of 100 degrees with 65% and 72%, respectively. CONCLUSIONS: Transvaginal sonographic assessment of cervical length and posterior cervical angle is better than conventional Bishop score in predicting successful labour induction in nulliparous women.     

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.     

Comparative study of induction of labor in nulliparous women with premature rupture of membranes at term compared to those with intact membranes: duration of labor and mode of delivery

AIM: To evaluate the effect of premature rupture of membranes (PROM) at term on the duration of labor and mode of delivery in comparison with intact membranes in nulliparous women with an unfavorable cervix whose labor was induced. METHODS: This retrospective cohort study included all term nulliparous women with an unfavorable cervix requiring labor induction over a 2-year period. Prostaglandin E(2) (dinoprostone) and oxytocin were used for labor induction. Criteria for enrolment included (i) singleton pregnancy; (ii) term nulliparous women; or (iii) Bishop score below 6. Statistics were analyzed with Student's t-test, chi(2)-test, Fisher's exact test, and multiple logistic regression. RESULTS: Our study subjects were 82 women whose labor was induced for PROM and 219 women with intact membranes whose labor was induced for social or fetal reasons. The mean durations of active phase of labor were not significantly different between women with PROM and those with intact membranes. However, the women with PROM had a significantly longer mean duration of second stage and a higher rate of cesarean delivery for failure to progress than those with intact membranes. Multiple logistic regression demonstrated that only PROM and fetal macrosomia were significantly associated with an increased risk of cesarean delivery for failure to progress after other confounding variables were adjusted. CONCLUSIONS: Labor induction for PROM at term in nulliparous women with an unfavorable cervix is associated with longer duration of the second stage and a higher risk of cesarean delivery for failure to progress in comparison to those with intact membranes.     

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.     

Risk of cesarean delivery after induction at term in nulliparous women with an unfavorable cervix

OBJECTIVE: The purpose of this study was to evaluate the effect of induction on the route of delivery in nulliparous women laboring at term in a community hospital system. STUDY DESIGN: From April 1997 to October 1999, there were 7282 deliveries in nulliparous patients who met inclusion criteria. Cesarean delivery rates were calculated for patients in spontaneous labor and for patients who underwent induction. RESULTS: Among 4635 women (63.7%) in spontaneous labor, the cesarean delivery rate was 11.5% versus 23.7% among the 2647 (36.3%) patients who underwent induction. An important variable that affected the delivery route was the Bishop score at the initiation of the induction. The cesarean delivery rate was 31.5% among patients whose Bishop score was <5 at induction versus 18.1% for patients with a score > or =5(P <.001). CONCLUSION: The induction of labor in nulliparous patients, especially those women with an unfavorable cervix as measured by Bishop score, is associated with a significantly increased risk of cesarean delivery.     

Extra-amniotic Foley catheter and prostaglandin E(2) gel for cervical ripening at term gestation.

OBJECTIVE: This study evaluated the efficacy of intravaginal prostaglandin E(2) gel in comparison with that of a Foley catheter for cervical ripening and induction of labor. STUDY DESIGN: Consecutive patients with unfavorable cervix requiring preinduction cervical ripening and induction of labor at term gestation were asked to participate in the study. One hundred and two patients were assigned to treatment with intravaginal prostaglandin E(2) gel (group 1) and 122 patients underwent the placement of an intracervical Foley catheter (group 2). After a maximum of three applications of intravaginal prostaglandin E(2) gel (18h) or after 18h from Foley catheter insertion oxytocin was administered to patients not in active labor. Labor profiles and pregnancy and neonatal outcome were compared between groups. RESULTS: The groups were comparable in term of demographic characteristics, indications for induction of labor, Bishop score at admission. The induction to labor time and the induction to delivery time were similar between groups. The cesarean sections rate was higher in group 1 than in group 2 (26.5 versus 14.7%, P<0.05). This remained significant when the analysis was restricted to nulliparous patients (32.3 versus 14.2%). The incidence of urinary tract infections, chorioamnionitis, and febrile morbidity was similar between groups. CONCLUSION: For preinduction cervical ripening, the Foley catheter is a valid alternative to the application of intravaginal prostaglandin E(2) gel and it is associated with a lower cesarean rate in nulliparous women.     

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.     

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.     

Impact of early admission in labor on method of delivery.

OBJECTIVE: The effect of the timing of admission in labor unit on the method of delivery was evaluated in a cohort study. METHOD: Four hundred and sixty six low-risk nulliparous women who were admitted in the labor unit in latent phase (group 1) were compared with 329 parturient women who were admitted in the active phase (group 2) to determine rate of and reasons for cesarean section, cervical dilation at the time of cesarean, and the rate of labor augmentation. RESULT: The number of cesarean deliveries in group 1 was greater than that in the group 2 (301 vs 80, p<0.0001 ). The main reason for cesarean section in group 1 was dystocia, and in 2, fetal distress. The rate of cesarean section in the women who were augmented was greater in group 1 than in group 2 (54% vs 23%, p<0.0001). CONCLUSION: Later admission in labor increases the rate of spontaneous vaginal delivery in low risk nulliparous women.     

Labor progression and risk of cesarean delivery in electively induced nulliparas

OBJECTIVE: To describe the pattern of labor progression and risk of cesarean delivery in women whose labor was electively induced. METHODS: We analyzed data on all low-risk, nulliparous women with an elective induction or spontaneous onset of labor between 37 + 0 and 40 + 6 weeks from January 2002 to March 2004 at a single institution. The median duration of labor by each centimeter of cervical dilation and the risk of cesarean delivery were computed for 143 women with preinduction cervical ripening and oxytocin induction, 286 women with oxytocin induction, and 1,771 women with a spontaneous onset of labor. An intracervical Foley catheter was used to ripen the cervix. RESULTS: Electively induced labor with cervical ripening had substantially slower latent and early active phases. After controlling for potential confounders, women who had an elective induction with cervical ripening had 3.5 times the risk of cesarean delivery during the first stage of labor (95% confidence interval 2.7-4.5), compared with those admitted in spontaneous labor. Elective induction without cervical ripening, on the other hand, was associated with a faster labor progression from 4 to 10 cm (266 compared with 358 minutes, P < .01) and did not increase the risk of cesarean delivery, compared with those in spontaneous labor. CONCLUSION: The pattern of labor progression differs substantially for women with an electively induced labor compared with those with spontaneous onset of labor. Furthermore, elective induction in nulliparous women with an unfavorable cervix has a high rate of labor arrest and a substantially increased risk of cesarean delivery. LEVEL OF EVIDENCE: II-2.     

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.