Randomized trial of isosorbide mononitrate versus misoprostol for cervical ripening at term

Comparison of the effect of oral and vaginal misoprostol on labor induction: updating a systematic review and meta-analysis of interventional studies

OBJECTIVES

This study is aimed to compare the effect of oral misoprostol with vaginal misoprostol to induce labor as a systematic review and meta-analysis.

METHODS

Electronic databases including PubMed [Medline], Scopus, Web of science, Embase, Ovid, Cochrane library, and ClinicalTrials.gov were searched using the relevant keywords. All RCTs comparing the effect of oral vs vaginal misoprostol on labor induction were considered. The Cochrane Risk of Bias checklist was used for assessing quality of included RCTs. All statistical analyses were completed using STATA (Version 16) and Revman (Version 5).

RESULTS

Thirty-three RCTs with 5162 patients (1560 in oral and 2602 in vaginal groups) were included in this meta-analysis. Labor induction length did differ significantly between the two routes of misoprostol administration [Standardized Mean Difference: 0.40 h, 95% confidence interval (CI) 0.34, 0.46; I²: 66.35%; P = 0.04]. In addition, the risk of neonatal death, tachysystole, uterine hyperstimulation, preeclampsia, non-FHR and abortion was lower in the oral misoprostol group and the risk of hypertonus, PROM, oxytocin need and cesarean fever was higher in this group than the vaginal misoprostol group.

CONCLUSIONS

Based on results of this meta-analysis, it can be inferred that currently, clinical specialists can decide to use this drug orally or vaginally on a case-by-case basis, depending on the condition of the pregnant mother and the baby.

Isosorbide mononitrate for cervical ripening in induction of labor for pregnant women with PROM at or post term

OBJECTIVE

To evaluate the efficacy of isosorbide mononitrate (IMN) for stimulating cervical ripening among pregnant women with premature rupture of membranes (PROM) at or post term.

METHODS

A prospective randomized double-blind, placebo-controlled trial at Kasr El-Ainy Hospital, Cairo, Egypt, from October 2018 to May 2019. Pregnant women at or post term with PROM and unfavorable cervix (Bishop score ≤6) were randomly assigned to receive intra-vaginal IMN (n = 70) or placebo (n = 70) before admission for induction of labor. The main outcome was induction to the delivery interval. Data were compared between groups by t test.

RESULTS

The mean ± SD duration from the initial dose of IMN/placebo to the beginning of the active phase of labor was significantly shorter in the IMN group than in the control group (9.7 ± 5.6 h vs. 12.9 ± 5.3 h). The IMN group also had a shorter time interval from induction to delivery (P < 0.01). There was no difference in adverse effects between the groups.

CONCLUSION

Intra-vaginal IMN for cervical ripening in the induction of labor among pregnant with PROM at or post term was found to be effective and safe with minimal adverse effects, and good neonatal and maternal outcomes. ClinicalTrials.gov: NCT03665779.

Evaluating the efficacy of outpatient use of isosorbide mononitrate on cervical ripening in pregnant women with unfavourable cervix

The aim of the present study was to evaluate the efficacy of outpatient administration of nitric oxide donor isosorbide mononitrate for cervical ripening. A randomised clinical trial was performed on term pregnant women with Bishop Score < 6. In the case group, Isosorbide-5-mononitrate capsule and in the control group, placebo was inserted in the posterior vaginal fornix for two consecutive days. The main outcomes were increases in Bishop Score after 48 hours of intervention, number of vaginal deliveries and interval from intervention to delivery.There was a significant increase of the mean Bishop score in the isosorbide group [3.57 ± 1.12 VS 1.54 ± 1.42 respectively (p = .001)]. The other outcome variables did not show a significant difference between the two groups except for headache which was significantly more in the case group. No cases of tachysystole were observed in the two groups. Additionally, haemoglobin levels after delivery did not show a significant difference between the two groups.Impact statement:What is already known on this subject? Cervical ripening in women with an unfavourable cervix and having an indication for induction of labour is an important issue in modern obstetrics. Different methods have been used for cervical ripening and induction of labour including mechanical (i.e. laminaria tents, Dilapan-S, foley catheter), medical (i.e. PGs) and supportive methods. There is no consensus on the best option for cervical ripeningWhat will the results of this study add to the current knowledge of this subject? Outpatient administration of nitric oxide could affect cervical ripening without a significant improvement in the duration of different stages of labour, intervention to delivery interval and number of vaginal deliveries.What are the implications of these findings for clinical practice and/or further research? Due to the contradictory results of various studies, more studies should be performed with greater sample size to evaluate nitric oxide donor isosorbide mononitrate effect on labour duration and reducing caesarean deliveries. Additional data is needed to assess the real impact of NO donors on different stages of labour and its implications.

A comparative randomized study on effect of vaginally administered glyceryl trinitrate placebo on cervical ripening prior to induction of labor in overdue pregnancies

OBJECTIVE:

The aim of this study is to examine the effectiveness and adverse effects of local glyceryl trinitrate (GTN) application during labor compared with a placebo group.

METHODS:

The study consisted of 70 pregnant women with overdue pregnancies who presented to the hospital for labor induction between January 2009 and January 2011 in the Obstetrics Clinic of Istanbul Süleymaniye Gynecology and Obstetrics Education and Training Hospital. Vaginal suppositories-containing GTN (36/70) or placebo (34/70) was administered to the participants in a randomized fashion. The placebo and GTN involving vaginal ovules used in the study were prepared in the Pharmacy Department of Istanbul University Faculty of Pharmacy. Maternal effects during labor, rates of normal vaginal and C/S deliveries, the interval between the initial medication and delivery, and amount of total oxytocin used were compared between the GTN and placebo groups.

RESULTS:

There were no significant differences between the GTN and placebo groups regarding bishop scores, the interval between medication and delivery, delivery types, indications for cesarean section, and complications including hyperstimulation, tachysystole, uterine rupture, placental abruption, and uterine atony (P > 0.05).

CONCLUSION:

Our results revealed that there were no differences between GTN and placebo regarding their effect on cervical ripening in overdue pregnant women.

Comparison of vaginal misoprostol, laminaria, and isosorbide dinitrate on cervical preparation and labor duration of term parturient: a randomized double-blind clinical trial

Background

Cervical ripening plays an important role in successful labor induction.

Objective

This study aimed to compare the effects of misoprostol, laminaria tent, and isosorbide dinitrate (ISDN) on cervical ripening.

Methods

This double-blind three-armed clinical trial was conducted at Shahidan Mombini Teaching Hospital in Sabzevar, Iran, in 2016 on 96 singleton term pregnant women. Participants were randomly allocated to receive either two 20-mg ISDN tablets vaginally every 4 hours for a maximum of three doses or 25 mcg misoprostol vaginally every 6 hours for a maximum of two doses or laminaria tent for a maximum of 12 hours. The method of randomization was covariate adaptive randomization and the primary outcome measures were Bishop Score changes and labor duration. SPSS software version 18 was used for statistical analyses. Kruskal-Wallis, chi-square and ANOVA tests were applied for data analyses.

Results

Bishop Score changes were higher in the misoprostol group than in the two other groups (p=0.014). Time from start of medication to active phase of labor and delivery were 6.22±3.11 and 11.78±5.3 minutes in the misoprostol group, 11.25±3.07 and 17.62±4.07 minutes in the laminaria group, and 10.12±3.48 and 17.37±4.79 minutes in the ISDN group respectively (p<0.001). Cesarean rate was higher in the misoprostol group than the two other groups (p=0.016). No significant differences were observed between the study groups in terms of Apgar score and meconium-stained amniotic fluid.

Conclusions

Use of misoprostol results in more improvement of Bishop Score and reduced length of labor phases in comparison to laminaria tent and ISDN.

Trial registration

The trial was registered at the Iranian Registry of Clinical Trials (http://www.irct.ir) with the Irct ID: IRCT2016050527643N2 in the Iranian Registry of Clinical Trials IRCT2015040921670N1.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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.

Nitric oxide donors for cervical ripening and induction of labour

BACKGROUND

Sometimes it is necessary to bring on labour artificially because of safety concerns for the mother or baby. This review is one of a series of reviews of methods of labour induction using a standardised protocol.

OBJECTIVES

To determine the effects of NO donors (isosorbide mononitrate (ISMN), isosorbide dinitrate (ISDN), nitroglycerin and sodium nitroprusside) for third trimester cervical ripening or induction of labour, in comparison with placebo or no treatment or other treatments from a predefined hierarchy.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (15 August 2016) and the reference lists of trial reports.

SELECTION CRITERIA

Clinical trials comparing NO donors for cervical ripening or labour induction with other methods listed above it on a predefined list of methods of labour induction. Interventions include NO donors (isosorbide mononitrate, isosorbide dinitrate, nitroglycerin and sodium nitroprusside) compared with other methods listed above it on a predefined list of methods of labour induction.

DATA COLLECTION AND ANALYSIS

This review is part of a series of reviews focusing on methods of induction of labour, based on a generic protocol. Three review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. In this update, the quality of the evidence for the main comparison was assessed using the GRADE approach.

MAIN RESULTS

We included 23 trials (including a total of 4777 women). Included studies compared NO donors with placebo, vaginal prostaglandin E2 (PGE2), intracervical PGE2, vaginal misoprostol and intracervical Foley catheter. The majority of the included studies were assessed as being at low risk of bias. Nitric oxide versus placebo There was no evidence of a difference for any of the primary outcomes analysed: vaginal delivery not achieved in 24 hours (risk ratio (RR) 0.97, 95% confidence interval (CI) 0.83 to 1.15; one trial, 238 women; low-quality evidence), uterine hyperstimulation with fetal heart rate (FHR) changes (RR 0.09, 95% CI 0.01 to 1.62; two trials, 300 women; low-quality evidence), caesarean section (RR 0.99, 95% CI 0.88 to 1.11; nine trials, 2624 women; moderate-quality evidence) or serious neonatal morbidity/perinatal death (average RR 1.61, 95% CI 0.08 to 33.26; two trials, 1712 women; low-quality evidence). There were no instances of serious maternal morbidity or death (one study reported this outcome).There was a reduction in an unfavourable cervix at 12 to 24 hours in women treated with NO donors (average RR 0.78, 95% CI 0.67 to 0.90; four trials, 762 women), and this difference was observed in both subgroups of standard release and slow release formulation. Women who received NO donors were less likely to experience uterine hyperstimulation without FHR rate changes (RR 0.05, 95% CI 0.00 to 0.80; one trial, 200 women), and more likely to experience side effects, including nausea, headache and vomiting. Nitric oxide donors versus vaginal prostaglandins There was no evidence of any difference between groups for uterine hyperstimulation with FHR changes or caesarean section (RR 0.97, 95% CI 0.78 to 1.21; three trials, 571 women). Serious neonatal morbidity and serious maternal morbidity were not reported. There were fewer women in the NO donor group who did not achieve a vaginal delivery within 24 hours (RR 0.63, 95% CI 0.47 to 0.86; one trial, 400 primiparae women). Nitric oxide donors versus intracervical prostaglandins One study reported a reduction in the number of women who had not achieved a vaginal delivery within 24 hours with NO donors (RR 0.63, 95% CI 0.47 to 0.86; one trial, 400 women). This result should be interpreted with caution as the information was extracted from an abstract only and a full report of the study is awaited. No differences were observed between groups for uterine hyperstimulation with FHR changes (RR 0.33, 95% CI 0.01 to 7.74; one trial, 42 women) or serious neonatal morbidity/perinatal death (RR 0.33, 95% CI 0.01 to 7.74; one trial, 42 women). Fewer women in the NO donor group underwent a caesarean section in comparison to women who received intracervical prostaglandins (RR 0.63, 95% CI 0.44 to 0.90; two trials, 442 women). No study reported on the outcome serious maternal morbidity or death. Nitric oxide donors versus vaginal misoprostol There was a reduction in the rate of uterine hyperstimulation with FHR changes with NO donors (RR 0.07, 95% CI 0.01 to 0.37; three trials, 281 women). There were no differences in caesarean section rates (RR 1.00, 95% CI 0.82 to 1.21; 761 women; six trials) and no cases of serious neonatal morbidity/perinatal death were reported. One study found that women in the NO donor group were more likely to not deliver within 24 hours (RR 5.33, 95% CI 1.62 to 17.55; one trial, 150 women). Serious maternal morbidity or death was not reported.In terms of secondary outcomes, there was an increase in cervix unchanged/unfavourable with NO (RR 3.43, 95% CI 2.07 to 5.66; two trials, 151 women) and an increase in the need for oxytocin augmentation with NO induction (RR 2.67, 95% CI 1.31 to 5.45; 7 trials; 767 women), although there was evidence of significant heterogeneity which could not be fully explained. Uterine hyperstimulation without FHR was lower in the NO group, as was meconium-stained liquor, Apgar score less than seven at five minutes and analgesia requirements. Nitric oxide donors versus intracervical catheter There was no evidence on any difference between the effects of NO and the use of a Foley catheter for induction of labour for caesarean section (RR 1.00, 95% CI 0.39 to 2.59; one trial, 80 women). No other primary outcomes were reported. One study of 75 participants did not contribute any data to the review.For all comparisons, women who received NO donors were more likely to experience side effects such as headache, nausea or vomiting.

AUTHORS' CONCLUSIONS

Available data suggests that NO donors can be a useful tool in the process of induction of labour causing the cervix to be more favourable in comparison to placebo. However, additional data are needed to assess the true impact of NO donors on all important labour process and delivery outcomes.

Outpatient cervical ripening

Induction of labor is one of the most commonly performed obstetric procedures. Many patients undergoing labor induction require cervical ripening. In an era where cost and patient satisfaction have become paramount, the idea of outpatient cervical ripening is appealing; provided it can be performed in a safe and cost effective manner. The ideal agent would induce adequate cervical ripening without causing significant uterine contractions/labor. Various methods have been studied including administration of misoprostol, PGE2, nitric oxide donors, use of Foley balloon catheters and acupuncture. Each method has its strengths and limitations; however, larger studies of outpatient cervical ripening that are specifically powered for rare adverse maternal and fetal outcomes are needed before definitive recommendations can be made.

Comparing the effect of oral and vaginal isosorbide dinitrate in pre-induction cervical ripening in term pregnancy: A controlled clinical trial

Background:

Cervical ripening for labor induction is one of the most important issues in midwifery. Isosorbide dinitrate (ISDN) is one of the most important choices that have been proposed for cervical ripening, but still there are controversies regarding its prescription. The present study aimed to evaluate the effects of vaginal and oral ISDN compared to the control group for pre-induction cervical ripening.

Materials and Methods:

In this non-blinded clinical trial, 149 nulliparous women with term or prolonged pregnancy were randomly selected and divided into three groups by block randomization. The intervention group included vaginal (50 subjects, 40 mg) and oral (49 subjects, 20 mg) ISDN groups. The third group was the control group (50 subjects) which did not receive any medication. The amount of ripening was given by Bishop score evaluated before taking medication and 24 h after taking it.

Results:

After 24 h, Bishop score in vaginal ISDN group significantly increased compared to the oral ISDN and control groups (P < 0.001 for both). Although the increase in Bishop score was lower in the oral ISDN group than in the vaginal group, it had a statistically significant increase in comparison to the control group (P = 0.001). All the three groups were matched regarding pregnancy termination and cesarean causes, and there was no statistically significant difference among the three groups (P > 0.05).

Conclusion:

Prescribing vaginal ISDN for cervical ripening was effective, and it can be used with confidence.

Isosorbide Mononitrate a Nitric Oxide Donor: A Study of Its Efficacy and Safety as an Agent for Cervical Ripening

OBJECTIVE

To study the efficacy and safety profile of isosorbide mononitrate (IMN) as an agent for cervical ripening.

METHODOLOGY

This study was conducted in the Department of Obstetrics and Gynecology, M Y Hospital & M G M Medical College Indore from September 2011 to February 2013. Pregnant women attending the antenatal clinics were screened for possible participation in the study after explaining the nature of the study. This study was conducted on 150 patients. An initial dose of 40 mg IMN was applied in the posterior vaginal fornix, and the same dose was repeated after 6 h. Cervical ripening was assessed by the change in Bishop Score 12 h after the initial application.

RESULTS

In a study of 150 cases, mean maternal age was 22.2 ± 2.6 years (range 19-35 years) and mean gestational age was 40.5 ± 1.07 (range 40-42 weeks). 52 women were primigravidas, while 98 were multigravidas. The mean Bishop Score-before drug administration was 1.94 ± 1.3 (range 0-5), and mean fetal heart rate was 137 ± 6.2 bpm. The mean of Bishop scores before IMN administration was 1.94 ± 1.3, while mean of Bishop score after drug administration was 6.7 ± 2.2; mean difference was equal to 4.76. P value was equal to 0.0001. By conventional criteria, this difference is considered to be statistically significant. The mode of delivery 96 (64 %) delivered vaginally, while 54 (36 %) were delivered by Cesarean section. Mean Apgar score at 1 min was 8.2 ± 0.9 SD (range 7-10), while mean Apgar score at 5 min was 9.4 ± 0.6 (range 8-10). The only side effect noted was headache, and 30 cases (20 %) complained of headache.

CONCLUSION

IMN seems to be effective, safe, inexpensive, and well-tolerated agent for cervical ripening. It is cost effective and safe with minimal side effects.

Comparing vaginal misoprostol versus Foley catheter plus vaginal isosorbide mononitrate for labor induction

OBJECTIVE(S)

To compare the effectiveness and safety of intra-cervical Foley catheter combined with intra-vaginal isosorbide mononitrate (IMN) versus intra-vaginal misoprostol for cervical ripening and labor induction in pregnant women with unripe cervices.

METHODS

Open-labeled randomized controlled trial in Cairo university hospital, Cairo, Egypt during 2012-2014. Three hundred and ninety-five pregnant women at term or post-term with an indication for labor induction and unripe cervix were included in the study. The subjects were randomly divided into two groups. Vaginal misoprostol was used in group 1 (n = 197) and intra-cervical Foley catheter plus vaginal IMN in group 2 (n = 198). Our main outcome measure was cesarean section rate.

RESULTS

Among the 395 included patients there were significantly lower duration of induction of labor (p < 0.001) in group 1with lower cesarean section rates [22.8% in group 1versus 33.3% in group 2; RR 0.7 (0.6-0.9), (p = 0.020)]. Whereas the uterine hyperstimulation (p < 0.001) was significantly higher in group 1. There were no significant differences between both groups as regard patients' demographic characteristics.

CONCLUSIONS(S)

Vaginal misoprostol is more effective but less safe than Foley catheter combined with vaginal IMN for induction of labor in term and post-term pregnancy.

Isonicotinic acid hydrazide (INH): A new agent for cervical ripening at term

The aim of this study was to assess the efficacy and safety of intravaginal isonicotinic acid hydrazide (INH) compared with misoprostol for cervical ripening at term. In this randomised controlled trial, 150 pregnant women, scheduled for labour induction, with Bishop's score (BS) ˂5, were recruited. They were assigned randomly to vaginal administration of isonicotinic acid hydrazide (INH) (900 mg) or misoprostol (25 μg), which were repeated every 4 h up to 3 times as needed. The efficacy of medications were evaluated by predetermined primary and secondary outcome variables for cervical ripening and induction of labour and delivery. Within the first 12 h of study, there was a significant increase in BS in each group. However, in the INH group changes in of BS were greater 12 h after starting the medication (p = 0.04). In the INH group, labour induction was needed more frequently, and the time from start of medication to the beginning of the active phase of labour and to the time of delivery were significantly longer (p˂0.001). Vaginal INH is an effective agent for cervical ripening at term.

Intravaginal isosorbide dinitrate or misoprostol for cervical ripening prior to induction of labour: a randomised controlled trial

In this randomised double-blind controlled trial, 130 healthy pregnant women with term pregnancy who scheduled for labour induction with Bishop's score < 5, were recruited. They were assigned randomly to vaginal administration of isosorbide dinitrate (ISDN) (40 mg) or misoprostol (25 μg), which were repeated after 4 h as needed. The efficacies of medications were evaluated by predetermined primary and secondary outcome variables for cervical ripening and induction of labour and delivery. There was no significant difference in Bishop's score 8 h after drug administration between the ISDN and misoprostol groups. However, in the ISDN group, labour induction was needed more frequently and the time from start of medication to the beginning of active phase of labour was significantly longer.

Randomized Comparison of Isosorbide Mononitrate and PGE2 Gel for Cervical Ripening at Term including High Risk Pregnancy

Aims. Prostaglandin E2 is the most commonly used drug for cervical ripening prior to labour induction. However, there are concerns regarding uterine tachysystole and nonreassuring fetal heart (N-RFH). Isosorbide mononitrate (IMN) has been used successfully for cervical ripening. The present study was conducted to compare the two drugs for cervical ripening at term in hospital. Methods. Two hundred women with term pregnancies referred for induction of labour with Bishop score less than 6 were randomly allocated to receive either 40 mg IMN tablet vaginally (n = 100) or 0.5 mg PGE2 gel intracervically (n = 100). Adverse effects, progress, and outcomes of labour were assessed. Results. PGE2 group had significantly higher postripening mean Bishop score, shorter time from start of medication to vaginal delivery (13.37 ± 10.67 hours versus 30.78 ± 17.29 hours), and shorter labour-delivery interval compared to IMN group (4.53 ± 3.97 hours versus 7.34 ± 5.51 hours). However, PGE2 group also had significantly higher incidence of uterine tachysystole (15%) and N-RFH (11%) compared to none in IMN group, as well as higher caesarean section rate (27% versus 17%). Conclusions. Cervical ripening with IMN was less effective than PGE2 but resulted in fewer adverse effects and was safer especially in high risk pregnancies.

Nitric oxide donors for cervical ripening and induction of labour

BACKGROUND

Sometimes it is necessary to bring on labour artificially because of safety concerns for the mother or baby. This review is one of a series of reviews of methods of labour induction using a standardised protocol.Induction of labour occurs in approximately 20% of pregnancies in the UK. The ideal agent for induction of labour would induce cervical ripening without causing uterine contractions. Currently most commonly used cervical ripening or induction agents result in uterine activity or contractions, or both. Cervical ripening without uterine contractility could occur safely in an outpatient setting and it may be expected that this would result in greater maternal satisfaction and lower costs.

OBJECTIVES

To determine the effects of nitric oxide (NO) donors for third trimester cervical ripening or induction of labour, in comparison with placebo or no treatment or other treatments from a predefined hierarchy.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2010) and the reference lists of trial reports and reviews.

SELECTION CRITERIA

Clinical trials comparing NO donors for cervical ripening or labour induction to other methods listed above it on a predefined list of methods of labour induction. The trials include some form of random allocation to either group; and report one or more of the prestated outcomes. NO donors (isosorbide mononitrate, nitroglycerin and sodium nitroprusside) are compared to other methods listed above it on a predefined list of methods of labour induction.

DATA COLLECTION AND ANALYSIS

This review is part of a series of reviews focusing on methods of induction of labour. Three review authors independently assessed trials for inclusion, assessed risk of bias and extracted data.

MAIN RESULTS

We considered 19 trials; we included 10 (including a total of 1889 women) trials, excluded eight trials and one trial report is awaiting classification. Included studies compared NO donors to placebo, vaginal prostaglandin E2, intracervical PGE2 and vaginal misoprostol. All included studies were of a generally high standard with a low risk of bias.There are very limited data available to compare nitric oxide donors to any other induction agent. There is no evidence of any difference between any of the prespecified outcomes when comparing NO donors to other induction agents, with the exception of an increase in maternal side effects.

AUTHORS' CONCLUSIONS

NO donors do not appear currently to be a useful tool in the process of induction of labour. More studies are required to examine how NO donors may work alongside established induction of labour protocols, especially those based in outpatient settings.

Oral misoprostol and vaginal isosorbide mononitrate for labor induction: a randomized controlled trial

OBJECTIVE

To estimate whether vaginal isosorbide mononitrate, added to oral misoprostol for cervical ripening and labor induction, shortens time to vaginal delivery.

METHODS

A prospective, randomized trial was conducted. Women scheduled for labor induction between 32 and 42 weeks and with unfavorable cervices (modified Bishop score 6 or lower) were randomized to receive oral misoprostol every 4 hours, up to four doses, with or without isosorbide mononitrate every 6 hours, up to two doses. A strict protocol was used, including timing of oxytocin use and amniotomy. Side effects were assessed 6 hours after study initiation. One hundred forty-two patients were required to detect a change in time to vaginal delivery of 4 hours (alpha=.05 and beta=.20). Data were analyzed by intent to treat. Student's t, chi square, Fisher's exact, and Mann-Whitney tests were used where appropriate with P< or =.05 deemed significant.

RESULTS

One hundred fifty-six women were randomized; three were excluded after randomization. Seventy-eight women received misoprostol, and 78 received misoprostol with isosorbide mononitrate. Demographic characteristics were similar between groups. The time to vaginal delivery was not reduced when isosorbide mononitrate was added to misoprostol. Cesarean delivery rates and contraction and fetal heart rate abnormalities were similar between groups. Side effects were also similar between groups, except that women given isosorbide mononitrate experienced headaches more often. Neonatal outcomes were similar between groups.

CONCLUSION

The addition of vaginal isosorbide mononitrate to oral misoprostol for cervical ripening and labor induction did not reduce time to vaginal delivery and was associated with a greater incidence of headache.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00374621.

LEVEL OF EVIDENCE

I.

Effect of isosorbide mononitrate for cervical ripening before surgical termination of pregnancy in the first trimester

OBJECTIVE

To evaluate the efficacy of isosorbide mononitrate (IMN) for cervical ripening prior to first trimester surgical termination of pregnancy.

METHODS

A prospective, double-blind, randomized, placebo-controlled trial. Women scheduled for surgical termination of a nonviable fetus before 12 weeks of gestation from October 2008 to June 2009 were enrolled and randomly assigned to receive either 20 mg vaginally of IMN (n=24) or a placebo (n=24) 4 hours before suction evacuation. Cervical dilation before evacuation was assessed with 10-mm Hegar dilators followed by smaller sizes that were measured until the instrument passed freely through the internal os. Cervical dilation, adverse effects, termination complications, and patient satisfaction were the main outcomes.

RESULTS

Mean cervical dilation was not significantly different between the IMN and placebo groups (6.29+/-0.99 mm vs 5.71+/-1.04 mm; P=0.05). Mean operative time did not differ between the groups (16+/-0.07 min vs 18+/-0.06 min; P=0.55), nor did patient satisfaction measured by visual analogue scale (7.04+/-1.68 vs 6.54+/-1.22; P=0.24).

CONCLUSION

IMN was comparable to placebo in terms of efficacy and patient satisfaction for cervical priming prior to first-trimester termination of pregnancy.

Outpatient vaginal administration of the nitric oxide donor isosorbide mononitrate for cervical ripening and labor induction postterm: a randomized controlled study

OBJECTIVE

Our aim was to examine the efficacy, safety, and acceptability of isosorbide mononitrate for cervical ripening and labor induction in women in an outpatient setting.

STUDY DESIGN

Two hundred pregnant women of at least 42 weeks' gestation with an unripe cervix were randomly selected to receive vaginally either 40 mg isosorbide mononitrate or placebo tablets.

RESULTS

Twenty-two women treated with isosorbide mononitrate went into labor within 24 hours compared to 8 women in the placebo group (P < .05). In women who did not go into labor, cervical status was similar in the 2 groups the next day. Headache was a common side effect. No maternal or fetal side effects of clinical importance were registered.

CONCLUSION

Outpatient cervical ripening and labor induction with isosorbide mononitrate seems to be an effective, safe, and well tolerated procedure. The definitive clinical efficacy and safety needs to be evaluated in larger series of patients.

Induction of labor at term using isosorbide mononitrate simultaneously with dinoprostone compared to dinoprostone treatment alone: a randomized, controlled trial

OBJECTIVE

We aimed to determine whether isosorbide mononitrate (IMN) given simultaneously with dinoprostone in term pregnancies is superior to dinoprostone alone to promote delivery.

STUDY DESIGN

One hundred and twenty nulliparous women at term were randomly assigned to receive per vaginam IMN 40 mg or placebo in addition to 3 mg dinoprostone 2 times daily for up to 2 days. Analysis was by intention to treat.

RESULTS

Baseline characteristics of both groups were comparable. The induction to delivery intervals did not differ between the IMN and the placebo group (26.4 +/- 14.4 vs 23.4 +/- 14.8 hours, P = .408). IMN resulted in more headache compared to placebo (32/55 [58.2%] vs 2/55 [3.6%], P < .001).

CONCLUSION

Vaginally administered IMN does not play a role in promoting delivery in term pregnancy if given at the same time as dinoprostone. This might reflect its relaxant effect on the uterine fundus, which may overcome its cervical softening effect.

IMOP: randomised placebo controlled trial of outpatient cervical ripening with isosorbide mononitrate (IMN) prior to induction of labour - clinical trial with analyses of efficacy, cost effectiveness and acceptability

Background

There is increasing interest in carrying out pre-induction cervical ripening on an outpatient basis. However, there are concerns about the use of prostaglandins, the agents commonly used in hospital settings for this indication, because prostaglandins induce uterine contractions that may lead to fetal hypoxia. Indeed, in a recent study we demonstrated abnormalities in 9% of fetal heart rate tracings performed following prostaglandin induced cervical ripening at term. In contrast, we confirmed in the same study that isosorbide mononitrate (IMN) (administered on an inpatient basis) was both effective in inducing cervical ripening at term, and was associated with no associated fetal heart rate abnormalities.

Methods/design

The aim of this study is to determine whether IMN self administered by women on an outpatient basis improves the process of induction of labour. Specifically, we hypothesise that the use of outpatient IMN will result in a shorter inpatient stay before delivery, decreased costs to the health service and greater maternal satisfaction with ripening and induction of labour, compared with placebo treatment.

In the study described here (the "IMOP" study), women scheduled for induction of labour at term, and who require pre-induction cervical ripening will be randomised to self-administer at home either IMN 40 mg, or a placebo, each vaginally, at 48 hours, 32 hours and 16 hours before scheduled hospital admission.

After admission to hospital, treatment will revert to the usual induction of labour protocol. We will compare the primary outcomes of the elapsed time interval from hospital admission to vaginal delivery, the costs to the health service of induction of labour, and women's experience of induction of labour in the two groups.

Discussion

This trial will provide evidence on the efficacy of outpatient IMN for pre-induction cervical ripening at term. We will study a formulation of IMN which is cheap and widely available. If the treatment is effective, acceptable to women, and cost effective, it could be implemented into obstetric practice worldwide.

Trial registration

The trial has been registered on the International Standard Randomised Controlled Trial Number Register (ISRCTN) and given the registration number ISRTN39772441.

Induction of labour at the start of the new millennium

Around 20% of all deliveries are preceded by labour induction, a proportion that has not varied dramatically over recent years. Fetal death was the only indication for labour induction centuries ago, while this is now a very rare indication, with prolonged pregnancy and maternal hypertensive disorders being the major indications for the last 50–60 years. Techniques for inducing labour have also changed from dietary delicacies and verbal threats giving way to physical stimulation mainly achieved by cervical stretching and amniotomy and more recently to sophisticated pharmacological manipulation using oxytocin and prostaglandins, based on our expanding knowledge of the physiological processes involved in spontaneous parturition. Relaxin, antiprogestins, nitric oxide as well as complementary medicines have also been explored in recent years. Successful induction is, however, still not guaranteed and there has been increasing emphasis during the past decade on exploring strategies for identifying the probability of success. Measurement of fetal fibronectin in cervical mucus, maternal serum nitrite/nitrate concentrations, ultrasound delineation of cervical form and electrical impedance measurements across the cervix are all being investigated. Safety, success, and patient satisfaction continue to be the major objectives with economic evaluations now becoming a significant factor in the search for the ideal induction method.

Intravaginal glyceryl trinitrate and dinoprostone for cervical ripening and induction of labor

OBJECTIVE

This study was undertaken to evaluate the efficacy and safety of intravaginal administration of glyceryl trinitrate plus dinoprostone versus dinoprostone, for cervical ripening and induction of labor.

STUDY DESIGN

A prospective, double-blind, placebo-controlled, randomized clinical trial was conducted among 196 singleton low-risk nullipara women with term pregnancies and unfavorable cervices who were randomly assigned to receive intravaginal glyceryl trinitrate plus dinoprostone or placebo plus dinoprostone. The main outcome variables were time from application to active phase of labor and to delivery. Secondary outcomes were change in Bishop score, fetal and maternal morbidity, and incidence of cesarean deliveries.

RESULTS

The interval from application of the initial dose to the beginning of active phase of labor was 868 +/- 582 and 1136 +/- 692 minutes (P = .004) and from initial dose to delivery was 1339 +/- 826 and 1620 +/- 975 minutes (P = .03) for the glyceryl trinitrate and placebo groups, respectively. There were no significant differences in Bishop score change, cesarean section rate, and in the incidence of hypersystole and hyperstimulation. The incidence of tachysystole was significantly lower in the glyceryl trinitrate group (4% vs 15%, P < or = .02). No maternal and neonatal adverse effects were noted.

CONCLUSION

The association of glyceryl trinitrate with dinoprostone is more effective than dinoprostone alone for labor induction in low-risk patients at term with unfavorable cervices.

The "PRIM" study: a randomized comparison of prostaglandin E2 gel with the nitric oxide donor isosorbide mononitrate for cervical ripening before the induction of labor at term

OBJECTIVE

The purpose of this study was to compare the efficacy and safety profile of prostaglandin E2 with isosorbide mononitrate for cervical ripening before the induction of labor at term.

STUDY DESIGN

Primigravid women were assigned randomly to receive either 40 mg of isosorbide mononitrate or 2 mg of prostaglandin E2. Efficacy outcomes were the cervical ripening effect of each agent and the time from treatment initiation to delivery. Safety outcomes were the incidence and frequency of maternal side effects and events that would be potentially hazardous for mother and baby during outpatient cervical ripening.

RESULTS

Prostaglandin E2 was more effective than isosorbide mononitrate in inducing a change in modified Bishop score. Mean duration from treatment initiation to delivery was greater for isosorbide mononitrate than prostaglandin E2. There were no adverse events in the isosorbide mononitrate group that would contraindicate outpatient treatment. However, in the prostaglandin E2 group, 7% of the pregnancies had abnormal fetal heart rate patterns (P = .0002). Maternal satisfaction was significantly higher in the isosorbide mononitrate group.

CONCLUSION

Although isosorbide mononitrate was less effective, maternal satisfaction was significantly greater. The safety profile of each agent was such that it would be reasonable to give isosorbide mononitrate, but not prostaglandin E2, on an outpatient basis.