The value of the cervical score in predicting successful outcome of labor induction

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix and induce labour. During recent decades they have been substituted by pharmacological methods. Potential advantages of mechanical methods, compared with pharmacological methods may include reduction in side effects that could improve neonatal outcomes. This is an update of a review first published in 2001, last updated in 2012.

OBJECTIVES

To determine the effectiveness and safety of mechanical methods for third trimester (> 24 weeks' gestation) induction of labour in comparison with prostaglandin E2 (PGE2) (vaginal and intracervical), low-dose misoprostol (oral and vaginal), amniotomy or oxytocin.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies (9 January 2018). We updated the search in March 2019 and added the search results to the awaiting classification section of the review.

SELECTION CRITERIA

Clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with pharmacological methods. Mechanical methods include: (1) the introduction of a catheter through the cervix into the extra-amniotic space with balloon insufflation; (2) introduction of laminaria tents, or their synthetic equivalent (Dilapan), into the cervical canal; (3) use of a catheter to inject fluid into the extra-amniotic space (EASI). This review includes the following comparisons: (1) specific mechanical methods (balloon catheter, laminaria tents or EASI) compared with prostaglandins (different types, different routes) or with oxytocin; (2) single balloon compared to a double balloon; (3) addition of prostaglandins or oxytocin to mechanical methods compared with prostaglandins or oxytocin alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed risk of bias. Two review authors independently extracted data and assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

This review includes a total of 112 trials, with 104 studies contributing data (22,055 women; 21 comparisons). Risk of bias of trials varied. Overall, the evidence was graded from very-low to moderate quality. All evidence was downgraded for lack of blinding and, for many comparisons, the effect estimates were too imprecise to make a valid judgement.   Balloon versus vaginal PGE2: there may be little or no difference in vaginal deliveries not achieved within 24 hours (risk ratio (RR) 1.01, 95% confidence interval (CI) 0.82 to 1.26; 7 studies; 1685 women; low-quality evidence) and there probably is little or no difference in caesarean sections (RR 1.00, 95% CI 0.92 to 1.09; 28 studies; 6619 women; moderate-quality evidence) between induction of labour with a balloon catheter and vaginal PGE2. A balloon catheter probably reduces the risk of uterine hyperstimulation with fetal heart rate (FHR) changes (RR 0.35, 95% CI 0.18 to 0.67; 6 studies; 1966 women; moderate-quality evidence), serious neonatal morbidity or perinatal death (RR 0.48, 95% CI 0.25 to 0.93; 8 studies; 2757 women; moderate-quality evidence) and may slightly reduce the risk of aneonatal intensive care unit (NICU) admission (RR 0.82, 95% CI 0.65 to 1.04; 3647 women; 12 studies; low-quality evidence). It is uncertain whether there is a difference in serious maternal morbidity or death (RR 0.20, 95% CI 0.01 to 4.12; 4 studies; 1481 women) or five-minute Apgar score < 7 (RR 0.74, 95% CI 0.49 to 1.14; 4271 women; 14 studies) because the quality of the evidence was found to be very low and low, respectively. Balloon versus low-dose vaginal misoprostol: it is uncertain whether there is a difference in vaginal deliveries not achieved within 24 hours between induction of labour with a balloon catheter and vaginal misoprostol (RR 1.09, 95% CI 0.85 to 1.39; 340 women; 2 studies; low-quality evidence). A balloon catheter probably reduces the risk of uterine hyperstimulation with FHR changes (RR 0.39, 95% CI 0.18 to 0.85; 1322 women; 8 studies; moderate-quality evidence) but may increase the risk of a caesarean section (RR 1.28, 95% CI 1.02 to 1.60; 1756 women; 12 studies; low-quality evidence). It is uncertain whether there is a difference in serious neonatal morbidity or perinatal death (RR 0.58, 95% CI 0.12 to 2.66; 381 women; 3 studies), serious maternal morbidity or death (no events; 4 studies, 464 women), both very low-quality evidence, and five-minute Apgar score < 7 (RR 1.00, 95% CI 0.50 to 1.97; 941 women; 7 studies) and NICU admissions (RR 1.00, 95% CI 0.61 to 1.63; 1302 women; 9 studies) both low-quality evidence. Balloon versus low-dose oral misoprostol: a balloon catheter probably increases the risk of a vaginal delivery not achieved within 24 hours (RR 1.28, 95% CI 1.13 to 1.46; 782 women, 2 studies, and probably slightly increases the risk of a caesarean section (RR 1.17, 95% CI 1.04 to 1.32; 3178 women; 7 studies; both moderate-quality evidence) when compared to oral misoprostol. It is uncertain whether there is a difference in uterine hyperstimulation with FHR changes (RR 0.81, 95% CI 0.48 to 1.38; 2033 women; 2 studies), serious neonatal morbidity or perinatal death (RR 1.11, 95% CI 0.60 to 2.06; 2627 women; 3 studies), both low-quality evidence, serious maternal morbidity or death (RR 0.50, 95% CI 0.05 to 5.52; 2627 women; 3 studies), very low-quality evidence, five-minute Apgar scores < 7 (RR 0.71, 95% CI 0.38 to 1.32; 2693 women; 4 studies) and NICU admissions (RR 0.82, 95% CI 0.58 to 1.17; 2873 women; 5 studies) both low-quality evidence.

AUTHORS' CONCLUSIONS

Low- to moderate-quality evidence shows mechanical induction with a balloon is probably as effective as induction of labour with vaginal PGE2. However, a balloon seems to have a more favourable safety profile. More research on this comparison does not seem warranted. Moderate-quality evidence shows a balloon catheter may be slightly less effective as oral misoprostol, but it remains unclear if there is a difference in safety outcomes for the neonate. When compared to low-dose vaginal misoprostol, low-quality evidence shows a balloon may be less effective, but probably has a better safety profile. Future research could be focused more on safety aspects for the neonate and maternal satisfaction.

Prevalence and risk factors for caesarean delivery following labor induction at a tertiary hospital in North Tanzania: a retrospective cohort study (2000-2015)

BACKGROUND

Labor induction is among the common and widely practiced obstetric interventions aiming at achieving vaginal delivery. However, cesarean section (CS) delivery incidences have been reported following its use. This study aimed at determining the prevalence and risk factors for caesarean delivery following labor induction among women who gave birth at a tertiary hospital in north-Tanzania.

METHODS

A hospital-based retrospective cohort study was designed using maternally-linked data from Kilimanjaro Christian Medical Centre (KCMC) birth registry among women who gave birth to singleton babies from the year 2000 to 2015. All induced deliveries done in this period were studied. Women with multiple pregnancy, missing information on delivery mode and those with history of CS delivery were excluded. Relative risk and 95% Confidence Interval for risk factors for CS delivery following labor induction were estimated using log-binomial regression models. Robust variance estimation was used to account for repeated deliveries from the same subject.

RESULTS

A total of 1088 deliveries were analysed. The prevalence of CS following labour induction was 26.75%. Independent risk factors for CS delivery were; primiparity (RR = 1.46; 95% CI: 1.18-1.81), high birthweight (RR =1.28; 95% CI: 1.02-1.61), post-term pregnancy (RR = 1.45; 95% CI: 1.09-1.93), and urban residence (RR =1.29; 95%CI: 1.05-1.58).

CONCLUSION

In patients undergoing labor induction, primiparity, high birthweight, post dates and urban residence were found to associate with an elevated risk of caesarean delivery. Assessment of these factors prior to labor induction intervention is warranted to reduce adverse pregnancy outcomes associated with emergency caesarean delivery.

The predictive value of cervical shear wave elastography in the outcome of labor induction

Introduction

Bishop score, the traditional method to assess cervical condition, is not a promising predictive tool of the outcome of labor induction. As an objective assessment tool, many cervical ultrasound measurements have been proposed to represent the individual components of the Bishop score, but none of them can measure the cervical stiffness. Cervical shear wave elastography is a novel tool to assess the cervical stiffness quantitatively.

Material and methods

A total of 475 women who required labor induction were studied prospectively. Prior to routine digital assessment of the Bishop score, transvaginal sonographic measurement of cervical length, posterior cervical angle, angle of progression and shear wave elastography was performed. Shear wave elastography measurement was made at the inner, middle and outer regions of the cervix to assess homogeneity. Association of labor induction outcomes including the overall cesarean section and subgroups of cesarean section for failure to enter active phase, with cervical sonographic parameters and the Bishop score, were assessed using multivariate regression analyses. The predictive accuracy of the outcomes using models based on ultrasound measurement and the Bishop score was compared using the area under the receiver‐operating characteristics curves.

Results

Among 475 women, 82 (17.3%) required cesarean section. Shear wave elasticity was significantly higher in the inner cervical region than in other regions, indicating a greater stiffness (P < 0.001). Both inner cervical shear wave elasticity and cervical length were independent predictors of overall cesarean section (respective adjusted odds ratio [95% CI] 1.338 [1.001‐1.598] and 1.717 [1.077‐1.663]) and cesarean section for failure to enter active phase (respective adjusted odds ratio [95% CI] 1.689 [1.234‐2.311] and 2.556 [1.462‐4.467]), after adjusting for other covariates. Outcome prediction models using inner cervical shear wave elasticity and cervical length, had increased area under curve compared with models using the Bishop score (0.888 vs 0.819, P = 0.009).

Conclusions

The cervix is not a homogenous structure, with the inner cervix having the highest stiffness, which is an independent predictor of overall cesarean section, and specifically for those indicated because of failure to enter active phase. Models based on shear wave elastography and cervical length had higher predictive accuracy than models based on the Bishop score.

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix and induce labour. During recent decades they have been substituted by pharmacological methods. Potential advantages of mechanical methods, compared with pharmacological methods may include reduction in side effects that could improve neonatal outcomes. This is an update of a review first published in 2001, last updated in 2012.

OBJECTIVES

To determine the effectiveness and safety of mechanical methods for third trimester (> 24 weeks' gestation) induction of labour in comparison with prostaglandin E2 (PGE2) (vaginal and intracervical), low-dose misoprostol (oral and vaginal), amniotomy or oxytocin.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP), and reference lists of retrieved studies (9 January 2018). We updated the search in March 2019 and added the search results to the awaiting classification section of the review.

SELECTION CRITERIA

Clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with pharmacological methods.Mechanical methods include: (1) the introduction of a catheter through the cervix into the extra-amniotic space with balloon insufflation; (2) introduction of laminaria tents, or their synthetic equivalent (Dilapan), into the cervical canal; (3) use of a catheter to inject fluid into the extra-amniotic space (EASI).This review includes the following comparisons: (1) specific mechanical methods (balloon catheter, laminaria tents or EASI) compared with prostaglandins (different types, different routes) or with oxytocin; (2) single balloon compared to a double balloon; (3) addition of prostaglandins or oxytocin to mechanical methods compared with prostaglandins or oxytocin alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed risk of bias. Two review authors independently extracted data and assessed the quality of the evidence using the GRADE approach.

MAIN RESULTS

This review update includes a total of 113 trials (22,373 women) contributing data to 21 comparisons. Risk of bias of trials varied. Overall, the evidence was graded from very-low to moderate quality. All evidence was downgraded for lack of blinding and, for many comparisons, the effect estimates were too imprecise to make a valid judgement.Balloon versus vaginal PGE2: there may be little or no difference in vaginal deliveries not achieved within 24 hours (average risk ratio (RR) 1.01, 95% confidence interval (CI) 0.82 to 1.26; 7 studies; 1685 women; I² = 79%; low-quality evidence) and there probably is little or no difference in caesarean sections (RR 1.00, 95% CI 0.92 to 1.09; 28 studies; 6619 women; moderate-quality evidence) between induction of labour with a balloon catheter and vaginal PGE2. A balloon catheter probably reduces the risk of uterine hyperstimulation with fetal heart rate (FHR) changes (RR 0.35, 95% CI 0.18 to 0.67; 6 studies; 1966 women; moderate-quality evidence), serious neonatal morbidity or perinatal death (RR 0.48, 95% CI 0.25 to 0.93; 8 studies; 2757 women; moderate-quality evidence) and may slightly reduce the risk of aneonatal intensive care unit (NICU) admission (RR 0.82, 95% CI 0.65 to 1.04; 3647 women; 12 studies; low-quality evidence). It is uncertain whether there is a difference in serious maternal morbidity or death (RR 0.20, 95% CI 0.01 to 4.12; 4 studies; 1481 women) or five-minute Apgar score < 7 (RR 0.74, 95% CI 0.49 to 1.14; 4271 women; 14 studies) because the quality of the evidence was found to be very low and low, respectively.Balloon versus low-dose vaginal misoprostol: it is uncertain whether there is a difference in vaginal deliveries not achieved within 24 hours between induction of labour with a balloon catheter and vaginal misoprostol (RR 1.09, 95% CI 0.85 to 1.39; 340 women; 2 studies; low-quality evidence). A balloon catheter probably reduces the risk of uterine hyperstimulation with FHR changes (RR 0.39, 95% CI 0.18 to 0.85; 1322 women; 8 studies; moderate-quality evidence) but may increase the risk of a caesarean section (average RR 1.28, 95% CI 1.02 to 1.60; 1756 women; 12 studies; I² = 45%; low-quality evidence). It is uncertain whether there is a difference in serious neonatal morbidity or perinatal death (RR 0.58, 95% CI 0.12 to 2.66; 381 women; 3 studies), serious maternal morbidity or death (no events; 4 studies, 464 women), both very low-quality evidence, and five-minute Apgar score < 7 (RR 1.00, 95% CI 0.50 to 1.97; 941 women; 7 studies) and NICU admissions (RR 1.00, 95% CI 0.61 to 1.63; 1302 women; 9 studies) both low-quality evidence.Balloon versus low-dose oral misoprostol: a balloon catheter probably increases the risk of a vaginal delivery not achieved within 24 hours (RR 1.28, 95% CI 1.13 to 1.46; 782 women, 2 studies, and probably slightly increases the risk of a caesarean section (RR 1.17, 95% CI 1.04 to 1.32; 3178 women; 7 studies; both moderate-quality evidence) when compared to oral misoprostol. It is uncertain whether there is a difference in uterine hyperstimulation with FHR changes (RR 0.81, 95% CI 0.48 to 1.38; 2033 women; 2 studies), serious neonatal morbidity or perinatal death (RR 1.11, 95% CI 0.60 to 2.06; 2627 women; 3 studies), both low-quality evidence, serious maternal morbidity or death (RR 0.50, 95% CI 0.05 to 5.52; 2627 women; 3 studies), very low-quality evidence, five-minute Apgar scores < 7 (RR 0.71, 95% CI 0.38 to 1.32; 2693 women; 4 studies) and NICU admissions (RR 0.82, 95% CI 0.58 to 1.17; 2873 women; 5 studies) both low-quality evidence.

AUTHORS' CONCLUSIONS

Low- to moderate-quality evidence shows mechanical induction with a balloon is probably as effective as induction of labour with vaginal PGE2. However, a balloon seems to have a more favourable safety profile. More research on this comparison does not seem warranted.Moderate-quality evidence shows a balloon catheter may be slightly less effective as oral misoprostol, but it remains unclear if there is a difference in safety outcomes for the neonate. When compared to low-dose vaginal misoprostol, low-quality evidence shows a balloon may be less effective, but probably has a better safety profile.Future research could be focused more on safety aspects for the neonate and maternal satisfaction.

Which method is best for the induction of labour? A systematic review, network meta-analysis and cost-effectiveness analysis

BACKGROUND

More than 150,000 pregnant women in England and Wales have their labour induced each year. Multiple pharmacological, mechanical and complementary methods are available to induce labour.

OBJECTIVE

To assess the relative effectiveness, safety and cost-effectiveness of labour induction methods and, data permitting, effects in different clinical subgroups.

METHODS

We carried out a systematic review using Cochrane methods. The Cochrane Pregnancy and Childbirth Group's Trials Register was searched (March 2014). This contains over 22,000 reports of controlled trials (published from 1923 onwards) retrieved from weekly searches of OVID MEDLINE (1966 to current); Cochrane Central Register of Controlled Trials (The Cochrane Library); EMBASE (1982 to current); Cumulative Index to Nursing and Allied Health Literature (1984 to current); ClinicalTrials.gov; the World Health Organization International Clinical Trials Registry Portal; and hand-searching of relevant conference proceedings and journals. We included randomised controlled trials examining interventions to induce labour compared with placebo, no treatment or other interventions in women eligible for third-trimester induction. We included outcomes relating to efficacy, safety and acceptability to women. In addition, for the economic analysis we searched the Database of Abstracts of Reviews of Effects, and Economic Evaluations Databases, NHS Economic Evaluation Database and the Health Technology Assessment database. We carried out a network meta-analysis (NMA) using all of the available evidence, both direct and indirect, to produce estimates of the relative effects of each treatment compared with others in a network. We developed a de novo decision tree model to estimate the cost-effectiveness of various methods. The costs included were the intervention and other hospital costs incurred (price year 2012-13). We reviewed the literature to identify preference-based utilities for the health-related outcomes in the model. We calculated incremental cost-effectiveness ratios, expected costs, utilities and net benefit. We represent uncertainty in the optimal intervention using cost-effectiveness acceptability curves.

RESULTS

We identified 1190 studies; 611 were eligible for inclusion. The interventions most likely to achieve vaginal delivery (VD) within 24 hours were intravenous oxytocin with amniotomy [posterior rank 2; 95% credible intervals (CrIs) 1 to 9] and higher-dose (≥ 50 µg) vaginal misoprostol (rank 3; 95% CrI 1 to 6). Compared with placebo, several treatments reduced the odds of caesarean section, but we observed considerable uncertainty in treatment rankings. For uterine hyperstimulation, double-balloon catheter had the highest probability of being among the best three treatments, whereas vaginal misoprostol (≥ 50 µg) was most likely to increase the odds of excessive uterine activity. For other safety outcomes there were insufficient data or there was too much uncertainty to identify which treatments performed 'best'. Few studies collected information on women's views. Owing to incomplete reporting of the VD within 24 hours outcome, the cost-effectiveness analysis could compare only 20 interventions. The analysis suggested that most interventions have similar utility and differ mainly in cost. With a caveat of considerable uncertainty, titrated (low-dose) misoprostol solution and buccal/sublingual misoprostol had the highest likelihood of being cost-effective.

LIMITATIONS

There was considerable uncertainty in findings and there were insufficient data for some planned subgroup analyses.

CONCLUSIONS

Overall, misoprostol and oxytocin with amniotomy (for women with favourable cervix) is more successful than other agents in achieving VD within 24 hours. The ranking according to safety of different methods was less clear. The cost-effectiveness analysis suggested that titrated (low-dose) oral misoprostol solution resulted in the highest utility, whereas buccal/sublingual misoprostol had the lowest cost. There was a high degree of uncertainty as to the most cost-effective intervention.

FUTURE WORK

Future trials should be powered to detect a method that is more cost-effective than misoprostol solution and report outcomes included in this NMA.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42013005116.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Diabetes mellitus: an independent predictor of duration of prostaglandin labor induction

OBJECTIVE

The objective of this study is to analyze the association of diabetes mellitus with progress and outcomes of prostaglandin (PG) labor induction using a retrievable vaginal insert.

STUDY DESIGN

This is a secondary analysis of data collected during the Misoprostol Vaginal Insert Trial (Miso-Obs-004), a multicenter, double-blind, randomized controlled trial of women undergoing induction of labor with PGs. The duration, characteristics and outcomes of labor were compared in women with and without diabetes. Multivariable regression analysis was performed on all outcomes of interest, adjusting for differences in baseline characteristics.

RESULTS

There were 122 women with diabetes within the sample of 1275 women who delivered during their first admission. The time to reach active labor was significantly prolonged among women with diabetes compared with those without (22.0±13.0 vs 18.5±11.1, P=0.008) as was the time to delivery (30.2±15.0 vs 26.0±12.6, P=0.004). Fewer women with diabetes delivered within 36 h (adjusted odds ratio: 0.41, 95% confidence interval: 0.26 to 0.66, P=0.0003) and 48 h (adjusted odds ratio: 0.36, 95% confidence interval: 0.19 to 0.71, P=0.004). These relationships were significant after a multivariate regression analysis of baseline characteristics that adjusted for age, race, parity, body mass index, baseline modified Bishop Score, gestational age at induction and treatment group allocation.

CONCLUSION

After PG labor induction, women with diabetes took longer to reach active labor and to deliver. We emphasize that this result comes from a secondary analysis and needs confirmation with additional studies.

[Are ultrasound measurements of the cervical length and fetal head-perineum distance predictive of delivery outcome in post-term pregnancies?]

OBJECTIVE

Post-term pregnancy is frequently associated with higher fetal and maternal morbidity and mortality. Its management essentially depends on clinical cervical characteristics as evaluated by the Bishop score (BS). However, BS is poorly predictive of the delivery outcome. We sought to demonstrate that ultrasound measurement of cervical length and evaluation of fetal height could predict the outcome in post-term pregnancies.

METHODS

A prospective single center study was undertaken between the 21st of January and the 1st of June 2013. Fetal height was measured using a transperineal technique and cervical length was evaluated by a vaginal ultrasound on patients consulting and their term date. C-section rates were considered to be the primary judgment criteria.

RESULTS

A total of 136 patients were included. C-section rates in this population was 19%. Fetal height and cervical length were not different between the C-section group and the vaginal delivery group.

CONCLUSION

Our study demonstrates that ultrasound measurement of cervical length and fetal height do not show better results than BS in predicting the outcome of post-term pregnancy. Combining these ultrasound measurements has already been suggested in other studies and promising results have been shown. More studies are necessary to further these results.

Factors associated with vaginal delivery in hypertensive and normotensive pregnant women submitted to labor induction with misoprostol: a cohort study

OBJECTIVE

To determine the factors associated with vaginal delivery in hypertensive and normotensive pregnant women submitted to induction of labor with misoprostol.

METHODS

A cohort study.

RESULTS

The factors associated with vaginal delivery in both normotensive and hypertensive women were, respectively, Bishop score ≥ 4 (OR = 1.87; 95% CI: 1.06-3.29; p = 0.03) and (OR = 2.31; 95% CI: 1.25-4.28; p = 0.008) and parity ≥ 1 (OR = 4.36; 95% CI: 2.16-8.80; p < 0.0001) and (OR = 2.61; 95% CI: 1.36-5.04; p = 0.004).

CONCLUSION

The factors associated with vaginal delivery were Bishop score ≥ 4 and parity ≥ 1 irrespective of whether or not the women were hypertensive.

[Adding parity to the Bishop score for term labor induction: a retrospective study]

OBJECTIVE

To evaluate the interest to add parity to the Bishop score before induction of labor by intravenous oxytocin.

PATIENTS AND METHODS

This retrospective cohort study compared cesarean section rate for induction failure by intravenous oxytocin in nulliparous and multiparous with modified Bishop score from 7 to 9. The modified Bishop score is calculated by adding 2 points to the Bishop score if the patient had a previous vaginal delivery and 0 point in nulliparous.

RESULTS

Over 2 years, 468 patients were included (201 nulliparous and 267 multiparous). Cesarean section rate for induction failure was higher for nulliparous with a modified Bishop score equal to 7 or varying between 7 and 9. These results confirm that parity is an important predicting factor of successful labor induction. In multiparous, cesarean section rates for induction failure were not significantly different with Bishop score or modified Bishop score equal to 7.

CONCLUSION

Adding 2 points for multiparity at the Bishop score did not increase cesarean for failure of labor induction with intravenous oxytocin with a modified Bishop score from 7 to 9.

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix and induce labour. During recent decades they have been substituted by pharmacological methods. Potential advantages of mechanical methods, compared with pharmacological methods, may include simplicity of preservation, lower cost and reduction of the side effects.

OBJECTIVES

To determine the effects of mechanical methods for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment, prostaglandins (vaginal and intracervical prostaglandin E2 (PGE2), misoprostol) and oxytocin.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 April 2011) and bibliographies of relevant papers. We updated this search on 16 January 2012 and added the results to the awaiting classification section of the review.

SELECTION CRITERIA

Clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with methods listed above it on a predefined list of methods of labour. A comparison with amniotomy will be added, should this comparison be made in future trials.Different types of intervention have been considered as mechanical methods: (1) introduction of laminaria tents, or their synthetic equivalent (Dilapan), into the cervical canal; (2) the introduction of a catheter through the cervix into the extra-amniotic space, with or without traction; (3) use of a catheter to inject fluidsin the extra-amniotic spaceIn addition, we made other comparisons: (1) specific mechanical methods (balloon catheter and laminaria tents) compared with any prostaglandins or with oxytocin; (2) addition of prostaglandins or oxytocin to mechanical methods compared with prostaglandins alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed risk of bias. Two review authors independently extracted data.

MAIN RESULTS

For this update we have included a further 27 studies. The review includes 71 randomised controlled trials (total of 9722 women), ranging from 39 to 588 women per study. Most studies reported on caesarean section, all other outcomes are based on substantially fewer women. Four additional studies are ongoing.Mechanical methods versus no treatment: one study (48 woman) reported on women who did not achieve vaginal delivery within 24 hours (risk ratio (RR) 0.90; 95% confidence interval (CI) 0.64 to 1.26). The risk of caesarean section was similar between groups (six studies; 416 women, RR 1.00; 95% CI 0.76 to 1.30). There were no cases of severe neonatal and maternal morbidity.Mechanical methods versus vaginal PGE2 (17 studies;1894 woman): The proportion of women who did not achieve vaginal delivery within 24 hours was not significantly different (three studies; 586 women RR 1.72; 95% CI 0.90 to 3.27); however, for the subgroup of multiparous women the risk of not achieving delivery within 24 hours was higher (one study; 147 women RR 4.38, 95% CI 1.74 to 10.98), with no increase in caesarean sections (RR 1.19, 95% CI 0.62-2.29). Compared with intracervical PGE2 (14 studies;1784 women and misoprostol there was no significant difference in the proportion of women not achieving vaginal delivery within 24 hours.Mechanical methods reduced the risk of hyperstimulation with fetal heart rate changes when compared with vaginal prostaglandins: vaginal PGE2 (eight studies; 1203 women, RR 0.16; 95% CI 0.06 to 0.39) and misoprostol (3% versus 9%) (nine studies; 1615 women, RR 0.37; 95% CI 0.25 to 0.54). Risk of caesarean section between mechanical methods and prostaglandins was comparable. Serious neonatal and maternal morbidity were infrequently reported and did not differ between the groups.Mechanical methods compared with induction with oxytocin (reduced the risk of caesarean section (five studies; 398 women, RR 0.62; 95% CI 0.42 to 0.90). The likelihood of vaginal delivery within 24 hours was not reported. Hyperstimulation with fetal heart rate changes was reported in one study (200 participants), and did not differ. There were no reported cases of severe maternal or neonatal morbidity.

AUTHORS' CONCLUSIONS

Induction of labour using mechanical methods results in similar caesarean section rates as prostaglandins, for a lower risk of hyperstimulation. Mechanical methods do not increase the overall number of women not delivered within 24 hours, however the proportion of multiparous women who did not achieve vaginal delivery within 24 hours was higher when compared with vaginal PGE2. Compared with oxytocin, mechanical methods reduce the risk of caesarean section.

Prediction of successful labor induction by evaluation of maternal symptoms at an early stage of the misoprostol induction protocol

OBJECTIVE

This prospective observational study evaluated maternal symptoms and characteristics that predict successful labor induction with oral misoprostol.

METHODS

A total of 244 consecutive women undergoing labor induction voluntarily completed a questionnaire about subjective sensations and pain scores during the induction protocol. Maternal and neonatal characteristics were collected retrospectively from patient files. On the first day of induction, oral misoprostol (50 μg) every 4 h up to three doses was used.

RESULTS

A total of 46% of the parturients delivered or reached the active phase of labor 24 h after the initial dose of misoprostol (ID). In the whole study, 87% of the women delivered vaginally. In multivariable analysis, rupture of membranes, cervical dilatation before the initial dose, maternal sensation of painful contractions at 8 h after the initial dose, and gestational age, were found to be associated with successful labor induction.

CONCLUSIONS

Maternal sensation of painful contractions 8 h after an ID is an independent predictive factor of successful labor induction (defined as delivery or active phase of labor 24 h after beginning of induction). Other independent predictive factors are rupture of membranes, cervical dilatation before the initial dose, and gestational age.

Induction of labor with prostaglandins for medical reasons: Determining explanatory variables of the induction to delivery time interval for vaginal deliveries and caesarean section

OBJECTIVE

Aim of the study was to examine the influence of the various medical indications on a successful induction of labor by prostaglandins and to determine the explanatory variables.

STUDY DESIGN

Retrospective analysis of 729 pregnancies, which fulfilled following criteria: only one medical indication for induction, 37 completed weeks of gestation or more, alive singleton pregnancy with cephalic presentation and induction with prostaglandins locally. The chosen endpoint was delivery.

RESULTS

The Kaplan-Meier curves demonstrating the percentage of deliveries in function of the time interval from induction to delivery showed a significant longer time interval for those without pre-labor rupture of membranes (PROM) than for those with PROM as indicated by log rank testing (vaginal deliveries and caesarean sections: hazard ratio=0.67, 95% CI=0.48-0.82, P<0.001; vaginal deliveries only: hazard ratio=0.65; 95% CI=0.45-0.80; P<0.001). In a similar way, those without diabetes had a shorter induction to delivery time interval than those with diabetes when all deliveries, including caesarean sections, were considered (hazard ratio=1.59; 95% CI=1.05-2.06; P=0.02), but there was a "borderline missed" statistical difference when only vaginal deliveries were considered (hazard ratio=1.48; 95% CI=0.96-2.03; P=0.08). Subsequently, univariate analysis in a Cox proportional hazards regression model was used to identify possible explanatory variables of the outcome, followed by multivariate analysis using the Cox proportional hazards regression model again in order to determine the independent contribution of each of these variables to the outcome. Uni- and multivariate analysis showed the cervix score, parity, the number of applied vaginal prostaglandin tablets, the gestational age and PROM to be significant explanatory variables of the induction to delivery time interval. Diabetes, body mass index and body weight were related to the outcome in a univariate analysis, but after adjustment in a multivariate analysis these variables were not significant.

CONCLUSION

PROM was the only medical reason to influence the outcome of an induction with prostaglandins locally, other significant explanatory variables were the cervix score, parity, the number of applied prostaglandin tablets and the gestational age, whereas other factors, such as diabetes, body mass index and body weight had no significant influence.

Predicting a failed induction

BACKGROUND

A failed induction usually refers to failure to progress to the active phase of labour; however, there is no consensus regarding when an induction has failed.

AIMS

To investigate the factors (particularly length of latent phase) that may influence mode of birth for women undergoing Syntocinon induction of labour.

METHODS

A retrospective analysis of 978 nulliparous women undergoing Syntocinon induction of labour following artificial or spontaneous rupture of membranes was performed.

RESULTS

As the length of the latent phase increased, the likelihood of birth by caesarean section increased significantly (P < 0.001). After ten hours of Syntocinon administration, the 8% of women not in the active phase of labour had approximately a 75% chance of being delivered by emergency caesarean section and after 12 h the chance was almost 90%. Multivariate analysis also suggested an association between birth by caesarean section and use of prostaglandin gel (P < 0.001) or mechanical methods of cervical priming (P = 0.004), maternal height < 155 cm (P = 0.020) and cervical dilation prior to commencement of Syntocinon (P = 0.018).

CONCLUSIONS

It would seem reasonable to continue a Syntocinon infusion for at least ten hours in women undergoing induction who have yet to reach the active phase of labour ( 4 cm), and unclear benefit in continuing an induction beyond 12 h. The duration of latent phase is a helpful predictor of subsequent mode of birth.

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

The aim of this study was to evaluate the value of transvaginal sonographic cervical measurement in predicting failed labor induction and cesarean delivery for failure to progress in nulliparous women. One hundred and sixty-one women scheduled for labor induction underwent transvaginal ultrasonography and digital cervical examinations. Logistic regression demonstrated that cervical length and gestational age at induction, but not the Bishop score, significantly and independently predicted failed labor induction. According to the receiver operating characteristic curves analysis, the best cut-off value of cervical length for predicting failed labor induction was 28 mm, with a sensitivity of 62% and a specificity of 60%. In terms of the likelihood of a cesarean delivery for failure to progress as the outcome variable, logistic regression indicated that maternal height and birth weight, but not cervical length or Bishop score, were significantly and independently associated with an increased risk of cesarean delivery for failure to progress. Transvaginal sonographic measurements of cervical length thus independently predicted failed labor induction in nulliparous women. However, the relatively poor predictive performance of this test undermines its clinical usefulness as a predictor of failed labor induction. Moreover, cervical length appears to have a poor predictive value for the likelihood of a cesarean delivery for failure to progress.

Cervical ripening with a Foley catheter: the role of pre- and postripening ultrasound examination of the cervix

OBJECTIVE

The objective of the study was to assess sonographic changes in cervical length and posterior cervical angle in women undergoing cervical ripening with an extraamniotic Foley catheter and to determine whether pre- and postripening ultrasound parameters could help predict successful cervical ripening and the outcome of labor induction.

STUDY DESIGN

Cervical length and posterior cervical angle were measured by transvaginal sonography in 155 women with a Bishop score of 4 or less before placement of a transcervical Foley catheter for cervical ripening. At the time of Foley removal, women who did not enter active labor underwent a second ultrasound assessment of the cervix. Outcome measures were successful ripening, vaginal delivery, vaginal delivery within 24 hours, and vaginal delivery achieved with the Foley only. Multiple logistic regression models were generated to identify pre- and postripening clinical and ultrasound parameters independently associated with successful induction.

RESULTS

Forty patients (25.8%) went into active labor after spontaneous expulsion or removal of the Foley, without any additional intervention. A successful cervical ripening was obtained with the transcervical catheter in 46 women (29.6%). One hundred six women (68.4%) had vaginal delivery. No correlation was found among maternal body mass index, maternal age, clinical cervical dilatation, sonographic posterior cervical angle, and any of the outcomes of interest. Multiple logistic regression showed that preripening sonographic cervical length was an independent predictor of successful ripening (odds ratio [OR] 10.2, 95% confidence interval [CI] 3.6 to 28.5), vaginal delivery (OR 2.6, 95% CI 1.2 to 5.5), vaginal delivery achieved with only Foley (OR 17.2, 95% CI 3.9 to 76.2), and vaginal delivery within 24 hours (OR 3.3, 95% CI 1.5 to 7.3). In the subgroup of women who did not enter labor with the transcervical Foley, at the time of catheter removal, a significant change was found in sonographic cervical length (33.1 mm [12.2 to 54.1] vs 24.0 mm [7.6 to 42], P < .0001] and sonographic posterior cervical angle (110 degrees C [70-160] vs 137 degrees C [88-170], P < .0001), compared with preripening findings. Transvaginal ultrasound cervical length was the only postripening characteristic that independently predicted vaginal delivery (OR 3.5, 95% CI 1.3 to 9.1).

CONCLUSION

Transvaginal sonography seems a useful diagnostic tool to assess objectively the efficacy of the Foley catheter as ripening method and helps predict the likelihood of a successful induction of labor in individual women who require preinduction cervical ripening.

Misoprostol compared with prostaglandin E2 for labour induction in women at term with intact membranes and unfavourable cervix: a systematic review*

BACKGROUND

Misoprostol is a commonly used prostaglandin to induce labour. A potential risk of induction, however, is caesarean delivery, especially in women with an unfavourable cervix.

OBJECTIVES

To evaluate the use of misoprostol, compared with prostaglandin E2 (PgE2), for labour induction in women at term with an unfavourable cervix and intact membranes.

SEARCH STRATEGY

PubMed, Medline, EMBASE and the Cochrane Library were searched for articles published in any language from January 1987 to December 2005, using the keywords 'misoprostol', 'labour/labor' and 'induction'.

SELECTION CRITERIA

We identified randomised trials of women at term (> or =37 weeks of gestation) with intact membranes and unfavourable cervix, undergoing labour induction with misoprostol, orally, vaginally, sublingually or buccally, compared with PgE2 vaginally or intracervically.

DATA COLLECTION AND ANALYSIS

Caesarean delivery was the primary outcome, with tachysystole and hyperstimulation as secondary outcomes. The primary analysis compared any misoprostol with any PgE2 for all women, with a subgroup analysis for nulliparous women. Secondary analyses compared different routes and doses of misoprostol (oral or vaginal and 25 microgram or >25 microgram) and PgE2 (intracervical or vaginal). Relative risks (RR) and 95% confidence intervals (CI) were calculated using random effects models. Main results Fourteen of 611 articles identified met the criteria for systematic review, with three providing information for nulliparous women. There was no difference in the risk of caesarean delivery between misoprostol and PgE2 groups (RR = 0.99, 95% CI = 0.83-1.17). Any misoprostol was associated with higher risks of tachysystole and hyperstimulation compared with any PgE2 (RR = 1.86, 95% CI = 1.01-3.43 and RR = 3.71, 95% CI = 2.00-6.88, respectively). There was a higher rate of vaginal delivery within 24 hours among all vaginal deliveries with any misoprostol compared with any PgE2 (RR = 1.14, 95% CI = 1.00-1.31), and among all deliveries, a lower rate of oxytocin use (RR = 0.71, 95% CI = 0.60-0.85) but a trend towards increased meconium staining was observed (RR = 1.22, 95% CI = 0.96-1.55). The use of misoprostol at starting dosages >25 microgram had similar findings to the primary analysis. Studies of lower misoprostol dosing (starting dose of 25 microgram) did not show any differences in the outcomes of interest, but the sample size of this secondary analysis was small (304 women, 155 receiving misoprostol).

AUTHOR'S CONCLUSIONS

Although misoprostol in women at term with an unfavourable cervix and intact membranes was more effective than PgE2 in achieving vaginal delivery within 24 hours, misoprostol does not reduce the rate of caesarean delivery either in all women or in the subgroup of nulliparous women, and it increases the rates of tachysystole and hyperstimulation. Further studies of misoprostol using a starting dose of 25 microgram may be warranted.

A way to lend objectivity to Bishop score

The aim of this study was to explore the possibility of utilising pre-induction cervical length assessment by trans-vaginal ultrasound to improve the predictive value of the Bishop score. The idea of this paper has evolved following our prospective study, which was designed to compare the pre-induction objective assessment of the cervix by ultrasound with the subjective one by Bishop Score. The Bishop scores of the 104 women included in the study were modified by replacing the digital assessment of the cervical length by ultrasound cervical length measurements. There was a significant statistical difference (p < 0.0001) between the median of the original and the modified Bishop scores. The original Bishop score showed insignificant association (p > 0.05) with the induction-delivery interval (IDI) and the mode of delivery while the modified score showed a significant association (r = 0.31, p < 0.05) with mode of delivery and a highly significant one (r = 0.55, p < 0.0001) with the IDI. The receiver operating characteristic curve showed that the optimised cut-off value for prediction of vaginal delivery was >5 for the original Bishop Score and >3 for the modified one. At those optimised cut-off values, the original Bishop Score predicted vaginal delivery with a sensitivity of 23% (95% CI; 14.6%, 33.2%) and specificity of 88.2% (95% CI; 63.5%, 98.5% while the modified Bishop score predicted vaginal delivery with a sensitivity of 62% [95%; CI 51 - 72.3] and specificity of 82% [95%; CI 56.6 - 96]). In conclusion, the modified Bishop score is better than the original one in predicting the IDI and the success of induction of labour. The sensitivity of the Bishop score in predicting the rate of vaginal delivery has been improved significantly following the modification.

Factors Predicting Labor Induction Success: A Critical Analysis

Because of the risk of failed induction of labor, a variety of maternal and fetal factors as well as screening tests have been suggested to predict labor induction success. Certain characteristics of the woman (including parity, age, weight, height and body mass index), and of the fetus (including birth weight and gestational age) are associated with the success of labor induction; with parous, young women who are taller and lower weight having a higher rate of induction success. Fetuses with a lower birth weight or increased gestational age are also associated with increased induction success. The condition of the cervix at the start of induction is an important predictor, with the modified Bishop score being a widely used scoring system. The most important element of the Bishop score is dilatation. Other predictors, including transvaginal ultrasound (TVUS) and biochemical markers [including fetal fibronectin (fFN)] have been suggested. Meta-analyses of studies identified from MEDLINE, PubMed, and EMBASE and published from 1990 to October 2005 were performed evaluating the use of TVUS and fFN in predicting labor induction success in women at term with singleton gestations. Both TVUS and Bishop score predicted successful induction [likelihood ratio (LR)=1.82, 95% confidence interval (CI)=1.51-2.20 and LR=2.10, 95%CI=1.67-2.64, respectively]. As well, fFN and Bishop score predicted successful induction (LR=1.49, 95%CI=1.20-1.85, and LR=2.62, 95%CI=1.88-3.64, respectively). Although TVUS and fFN predicted successful labor induction, neither has been shown to be superior to Bishop score. Further research is needed to evaluate these potential predictors and insulin-like growth factor binding protein-1 (IGFBP-1), another potential biochemical marker.

[Evaluation of controlled-release dinoprostone Propess for labor induction]

OBJECTIVE

To evaluate the efficacy of cervix ripening with vaginal controlled-release Propess.

PATIENTS AND METHODS

A retrospective study of all women who underwent cervical ripening with Propess during the study period from 1(st) January 2002 to 31(st) December 2004 was carried out. A total of 130 patients who experienced Propess was compared with the next following patient who delivered spontaneously matched on gestational age. Modes of delivery, failure of labor, maternal morbidity were recorded.

RESULTS

Indications for induction of labor were: post-term pregnancies in 18.5%, pre-eclampsia in 20.8%, oligohydroamnios in 18.5%, post-term pregnancy and oligohydramnios in 10.8%, intra-uterine fetal growth in 6.9%, premature rupture of membranes in 6.9%, diminution of fetal mobility in 6.1% and miscellaneous in 11.5%. Failure of cervical ripening was 21.2%. Patients in the Propess group had a 3.5 fold higher risk of Cesarean section [95% CI: 1.5-8.3; P < 0.04]. There was no case of maternal or fetal death. There was no difference in incidence of maternal complications, and post-partum haemorrhage.

DISCUSSION AND CONCLUSION

Use of vaginal pessary Propess does not induce adverse maternal or fetal morbidity. However, it was associated with a higher incidence of Cesarean delivery.

Clinical and Ultrasound Parameters to Predict the Risk of Cesarean Delivery After Induction of Labor

OBJECTIVE

To evaluate whether factors in the maternal history and/or ultrasound parameters are useful in predicting the risk of cesarean delivery after induction of labor.

METHODS

Maternal age, height, body mass index, parity, gestational age, Bishop score, ultrasonic amniotic fluid volume, fetal head position, estimated fetal weight, and transvaginal cervical length were studied prospectively in 267 women at 36 or more weeks of gestation immediately before induction of labor. Logistic regression analysis was used to determine which factors best predicted the risk of cesarean delivery. Receiver operating characteristic curves and a resampling technique were used to evaluate the model's performance.

RESULTS

Eighty (30%) of these 267 women had cesarean delivery. Logistic regression was performed and a final model chosen, which included parity (odds ratio [OR] 20.56, 95% confidence interval [CI] 7.97-53.05, P < .001), body mass index (OR 6.17, 95% CI 2.10-18.13, P < .001), height (OR 0.94, 95% CI 0.89-0.98, P = .005), and ultrasonic transvaginal cervical length (OR 1.07, 95% CI 1.04-1.11, P < .001) as the best predictors of cesarean delivery. A risk score was calculated containing these 4 parameters, which predicted reasonably accurately the risk of cesarean delivery.

CONCLUSION

Parity, body mass index, height, and ultrasonic transvaginal cervical length are the most accurate parameters in predicting the risk of cesarean delivery after induction of labor. A predictive model using these would allow more accurate counseling and better informed consent in the decision-making process regarding induction of labor

LEVEL OF EVIDENCE

II-2.

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.

Fetal Fibronectin as a Predictor of Vaginal Birth in Nulliparas Undergoing Preinduction Cervical Ripening

OBJECTIVE

We sought to evaluate whether the presence of a positive fetal fibronectin (> or = 50 ng/mL) in nulliparous women undergoing preinduction cervical ripening with the intracervical Foley catheter predicted vaginal birth.

METHODS

This was a prospective blinded observational trial of nulliparous women undergoing preinduction cervical ripening. We excluded women who had a contraindication to vaginal birth. Cervical and vaginal fetal fibronectin specimens were obtained before preinduction cervical ripening with an intracervical Foley catheter. The managing obstetrician was blinded to these results.

RESULTS

A total of 241 women met the inclusion criteria, of which 54.4% delivered vaginally. There was no difference in the rate of vaginal delivery among women with either a positive cervical fetal fibronectin (positive fetal fibronectin 55.8% compared with negative fetal fibronectin 53.3%, P = .70) or positive vaginal fetal fibronectin (positive fetal fibronectin 57.6% compared with negative fetal fibronectin 53.3%, P = .56). Women with a positive cervical fetal fibronectin did have a shorter duration of cervical ripening (fetal fibronectin-positive 229 +/- 220 minutes compared with fetal fibronectin-negative 379 +/- 193 minutes, P < .05), duration of oxytocin (fetal fibronectin-positive 655 +/- 555 minutes compared with fetal fibronectin-negative 731.5 +/- 342 minutes, P < .025) and required lower maximal doses of oxytocin (fetal fibronectin-positive 18.4 mIU/min compared with fetal fibronectin-negative 21.8 mIU/min, P = .005). Women with a positive vaginal fetal fibronectin demonstrated only a shorter duration of cervical ripening compared with their fetal fibronectin negative counterparts (fetal fibronectin-positive 300 +/- 216 minutes compared with fetal fibronectin-negative 345 +/- 201 minutes, P < .05).

CONCLUSION

Fetal fibronectin does not predict vaginal delivery in nulliparous women requiring preinduction cervical ripening.

LEVEL OF EVIDENCE

II-2.

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.

Protocol audit of dinoprostone gel induction of labour

This study aimed to evaluate dinoprostone gel induction of labour. A prospective observational study was conducted over six months in 2001. Themes explored include predictive indicators within the Modified Bishop's Score, timing between doses, timing of administration and number of doses administered. Labouring after one dose of dinoprostone gel is significantly related to a Modified Bishop's Score of > 4 (p = 0.005) and position of the cervix (p = 0.031) for all women, and for multiparous women cervical dilatation (p = 0.014). Timing of administration will not affect timing of delivery. There is no benefit in waiting more than six to eight hours between doses.

The role of ultrasound and fetal fibronectin in predicting the length of induced labor when the cervix is unfavorable

OBJECTIVE

To compare cervical clinical data, ultrasound parameters and fetal fibronectin assessment in the prediction of the duration of induced labor when the cervix is unfavorable.

METHODS

This was a prospective study of 90 pregnant women with a Bishop score </= 5 undergoing labor induction. The Bishop score and its components, parity, cervical ultrasound parameters and fetal fibronectin level were analyzed using Cox's model in order to determine the most predictive factors for the duration of the latent and active phases of labor as well as its total duration.

RESULTS

There was a significant correlation between duration of the latent phase and the whole of labor, and digitally assessed cervical dilatation (P = 0.003 and P < 0.001, respectively), parity (P = 0.006 and P < 0.001), the Bishop score (P = 0.019 and P = 0.003) and ultrasound-determined cervical length (P = 0.035 and P = 0.003). The length of the active phase of labor did not correlate with the cervical status. Funneling did not appear to be predictive of the duration of labor and it had a poor correlation with digital cervical dilatation. The length of the latent phase and that of the whole of labor was significantly longer when cervical dilatation was </= 2 cm (P < 0.001 in each case), when women were nulliparous (P = 0.002 and P < 0.001) and when ultrasound cervical length was >/= 27 mm (P = 0.002 and P = 0.005).

CONCLUSION

Cervical dilatation as assessed by digital examination is the best predictor of the duration of the latent phase and of that of the whole of labor. Ultrasound measurement of cervical length is not more accurate at predicting the duration of labor than are clinical data.

Does ultrasound examination when the cervix is unfavorable improve the prediction of failed labor induction?

OBJECTIVE

To compare the Bishop score, ultrasound cervical parameters and fetal fibronectin assessment for predicting failed labor induction when the cervix is unfavorable.

METHOD

A prospective observational study was performed in 106 consecutive pregnant women with a Bishop score < or =5 undergoing labor induction. Assessment of fetal fibronectin and ultrasound measurement of cervical length, cervical wedging and cervical lip areas were performed. The relationship between these parameters and failure of labor induction was determined.

RESULTS

Failure of labor induction was defined as failure to reach a cervical dilatation of > or =5 cm, and it occurred in 16 patients (15.1%). Induction failure was associated with low Bishop scores before (P = 0.004) and 6 h after the start of induction (P = 0.007), increased clinical cervical length (P = 0.02) and increased ultrasound anterior cervical lip area (P = 0.04). The logistic regression model identified the Bishop score before induction (odds ratio = 2.25; 95% CI, 1.30-3.91; P = 0.003) and the clinical cervical length (odds ratio = 3.95; 95% CI, 1.3-11.7; P = 0.01) as being independent predictors of failed induction. To predict an induction failure, the best Bishop score cut-off value was 4, with a sensitivity of 87.5%, a specificity of 45.6%, a likelihood ratio of 1.58, a positive predictive value of 22.2% and a negative predictive value of 95.4%.

CONCLUSION

Compared with the Bishop score, cervical length by ultrasound is not a better predictor for the outcome of labor induction in an unfavorable cervix. Nevertheless, the Bishop score appears to be of poor predictive value for failed induction of labor.

Transvaginal ultrasonography for cervical assessment before induction of labor

OBJECTIVE

To evaluate the value of ultrasonographic cervical assessment in predicting the outcome of labor induction and to compare its performance against the Bishop score.

METHODS

The Bishop score was determined by digital examination, and transvaginal ultrasonography was performed in 105 women at 37 to 42 weeks' gestation scheduled for labor induction. Ultrasonographic parameters evaluated were cervical length, the presence of funneling, funnel width, and funnel length and were blinded to managing physicians. The primary outcome was the occurrence of active labor within 2 days (successful labor induction). The interval from the onset of induction to active labor (duration of induction) was the secondary outcome. Statistical analysis was performed by the chi2 test, Wilcoxon rank sum test, Pearson correlation, receiver operating characteristic curves, logistic regression, Cox proportional hazards model, and generalized Wilcoxon test for survival data.

RESULTS

Induction of labor was successful in 93 women (89%). The area under the receiver operating characteristic curve for cervical length was greater than that of the Bishop score in predicting a successful labor induction (z = 2.18; P < .05). A cervical length of 3.0 cm or less had sensitivity of 75% (70 of 93) and specificity of 83% (10 of 12). Multiple logistic regression analysis showed a significant relationship between successful labor induction and cervical length but not the Bishop score (odds ratio = 0.24; 95% confidence interval, 0.096-0.59; P = .002). Only parity and cervical length had a significantly independent relationship with the duration of induction.

CONCLUSIONS

Cervical length measured by transvaginal ultrasonography is a useful and independent predictor of successful labor induction and the duration of induction and provides better predictability of successful labor induction than the Bishop score does.

Induction of labour with a favourable cervix and/or pre-labour rupture of membranes

Premature rupture of membranes (PROM) occurs in 8% of term deliveries. In this situation labour induction with prostaglandins, compared with expectant management, results in a reduced risk of chorioamnionitis, neonatal antibiotic therapy, neonatal intensive care (NICU) admission, and increased maternal satisfaction. The use of prostaglandin is associated with an increased rate of diarrhoea and use of analgesia/anaesthesia. Compared with oxytocin, prostaglandin induction results in a lower rate of epidural use and internal fetal heart rate monitoring but a greater risk of chorioamnionitis, nausea, vomiting, more vaginal examinations, neonatal antibiotic therapy, NICU admission and neonatal infection. Women should be informed of the risks and benefits of each method of induction.Misoprostol is gaining increasing interest as an alternative induction agent. It appears to be an effective method of labour induction with term PROM. Further research is needed to identify the preferred dosage, route and interval of administration, and to assess uncommon maternal and neonatal outcomes. There has been limited research on the use of prostaglandins, including misoprostol, for induction of labour with a favourable cervix and intact membranes. Compared with intravenous oxytocin (with and without amniotomy), labour induction using vaginal prostaglandins in women with a favourable cervix (with and without PROM) results in a higher rate of vaginal delivery within 24 hours and increased maternal satisfaction. In women with a favourable cervix, artificial rupture of membranes followed by oral misoprostol has similar time to vaginal delivery compared with artificial rupture of membranes followed by oxytocin. Further research with prostaglandins, including misoprostol, is needed to evaluate other maternal and neonatal outcomes in women being induced with a favourable cervix. No form of prostaglandin induction in women with PROM or favourable cervix has proven clearly superior to oxytocin infusion.

Transvaginal sonography of the uterine cervix prior to labor induction

OBJECTIVES

To compare the Bishop score and transvaginal sonographic measurement of cervical length for predicting the mode of delivery following medically indicated induction of labor in term patients.

METHODS

The study was conducted prospectively in 179 women who required medically indicated induction of labor. Inclusion criteria were singleton pregnancy, gestational age > 37 weeks of amenorrhea, cephalic presentation and intact fetal membranes. Cervical length was measured upon arrival in the labor room but was not considered when choosing the induction procedure. Two receiver-operating characteristic curves were plotted to calculate the best threshold value for the Bishop score and for cervical length for predicting the risk of Cesarean section.

RESULTS

Fifty-three women (29.6%) had a Cesarean section. The Bishop score was not predictive of the delivery mode, although Cesarean section for failure to progress was more frequent when the Bishop score was < or = 5. Among the women with a Bishop score > 5, the cervical length was not predictive of the induction outcome. However, among the women with a Bishop score < or = 5, a cervical length < 26 mm was associated with a lower Cesarean section rate (20.6 vs. 42.9%; P = 0.006). Furthermore, the interval between the beginning of cervical ripening and delivery was shorter in the case of a short cervix (11.01 +/- 6.7 vs. 18.55 +/- 7.07 h; P < 10(-5)).

CONCLUSION

The length of the uterine cervix, measured by transvaginal sonography, is a better predictor of the risk of Cesarean section than the Bishop score after induction of labor for medical reasons. In women with an unfavorable Bishop score, a cervical length of < 26 mm is associated with a lower risk of Cesarean section and a shorter duration of labor.

Mechanical methods for induction of labour

BACKGROUND

Mechanical methods were the first methods developed to ripen the cervix or to induce labour. Devices which were used include various type of catheters and of laminaria tents, introduced into the cervical canal or into the extra-amniotic space. Mechanical methods were never completely abandoned, but were substituted by pharmacological methods during recent decades. Potential advantages of mechanical methods, compared with pharmacological methods, may include simplicity of preservation, lower cost and reduction of the side effects. However, special attention should be paid to contraindications (e.g. low-lying placenta), risk of infection and maternal discomfort when inserting these devices. This is one of a series of reviews of methods of cervical ripening and labour induction using standardised methodology.

OBJECTIVES

To determine the effects of mechanical methods for third trimester cervical ripening or induction of labour in comparison with placebo/no treatment, prostaglandins (vaginal, intracervical, misoprostol) and oxytocin.

SEARCH STRATEGY

The Cochrane Pregnancy and Childbirth Group Trials Register, the Cochrane Controlled Trials Register and bibliographies of relevant papers. Last searched April 2001.

SELECTION CRITERIA

The criteria for inclusion were the following: (1) clinical trials comparing mechanical methods used for third trimester cervical ripening or labour induction with placebo/no treatment or other methods listed above it on a predefined list of labour induction methods; (2) random allocation to the treatment or control group; (3) adequate or unclear method for allocation concealment; (4) violations of allocated management not sufficient to materially affect conclusions; (5) clinically meaningful outcome measures reported; (6) data available for analysis according to the random allocation; (7) missing data insufficient to materially affect the conclusions.

DATA COLLECTION AND ANALYSIS

A strategy has been developed to deal with the large volume and complexity of trial data relating to labour induction. This involved a two-stage method of data extraction. The initial data extraction was done centrally, and incorporated into a series of primary reviews arranged by methods of induction of labour, following a standardised methodology. The data will be extracted from the primary reviews into a series of secondary reviews, arranged by category of woman.

MAIN RESULTS

In total, 58 studies were considered; 45 studies have been included and 13 were excluded. Studies generally included women with unfavourable cervix and intact membranes. Comparing mechanical methods with placebo/no treatment, only one study with 48 participants reported on vaginal delivery not achieved in 24 hours (69% with mechanical methods versus 77% with placebo/no treatment; relative risk (RR) 0.90; 95% confidence interval (CI): 0.64-1.26). Hyperstimulation with fetal heart rate changes was not reported. The risk of caesarean section, reported in six studies including 416 women, was similar between groups (34%; RR 1.00; 95% CI: 0.76-1.30). There were no reported cases of severe neonatal and maternal morbidity. Comparing mechanical methods with vaginal PGE2, only one trial (109 women) reported on vaginal delivery not achieved in 24 hours (73% versus 42%; relative risk (RR) 1.74; 95% CI: 1.21-2.49). Compared with intracervical PGE2, only one trial (100 women) reported on vaginal delivery not achieved in 24 hours (68% versus 40%; relative risk (RR) 1.70; 95% CI: 1.15-2.51). Compared with with misoprostol, the effectiveness of mechanical methods was similar (34% versus 30%; relative risk (RR) 1.15; 95% CI: 0.80-1.66). The use of mechanical method reduced the risk of hyperstimulation with fetal heart rate changes when compared with prostaglandins: vaginal PGE2 (0% versus 6%; RR 0.14; 95% CI: 0.04-0.53), intracervical PGE2 (0% versus 1%; RR 0.21; 95% CI: 0.04-1.20) and misoprostol (4% versus 9%; RR 0.41; 95% CI: 0.20-0.87). There was no difference in the risk of caesarean section between mechanical methods and prostaglandins. Serious neonatal (three cases) and maternal morbidity (one case) were infrequently reported. When compared with oxytocin, use of mechanical methods reduced the risk of caesarean section (4 trials; 198 women; 17% versus 32%; RR 0.55; 95% CI: 0.33-0.91). The likelihood of vaginal delivery in 24 hours and of hyperstimulation with fetal heart rate changes was not reported. There were no reported cases of serious maternal morbidity and severe neonatal morbidity was not reported. These results are similar whatever specific mechanical method was used, except with extra-amniotic infusion. When comparing extra-amniotic infusion with any prostaglandins, women were more likely to not achieve vaginal delivery within 24 hours (57% versus 42%; RR 1.33; 95% CI: 1.02-1.75), the risk of caesarean section was increased (31% versus 22%; RR 1.48; 95% CI: 1.14-1.90), without a reduction of the risk of hyperstimulation.

REVIEWER'S CONCLUSIONS

There is insufficient evidence to evaluate the effectiveness, in terms of likelihood of vaginal delivery in 24 hours, of mechanical methods compared with placebo/no treatment or with prostaglandins. The risk of hyperstimulation was reduced when compared with prostaglandins (intracervical, intravaginal or misoprostol). Compared to oxytocin in women with unfavourable cervix, mechanical methods reduce the risk of caesarean section. There is no evidence to support the use of extra-amniotic infusion.

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.

Cervical ripening

Induction of labor is indicated when the benefits to either the mother or the fetus outweigh the benefits of continuing the pregnancy. The state of the cervix is clearly related to the success of labor induction and the duration of labor. In cases of unfavorable cervices, physicians usually use a ripening agent before inducing labor. Unfortunately, as reviewed in this article, the ideal ripening agent is not found yet. No method of cervical ripening has shown a consistent and significant reduction in CS rate. In fact, women with the most unfavorable cervices (Bishop score, < or = 2) still face high rates of induction failure and CS.