Vaginal application of the nitric oxide donor isosorbide mononitrate for preinduction cervical ripening: a randomized controlled trial to determine effects on maternal and fetal hemodynamics

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Signaling Pathways Regulating Human Cervical Ripening in Preterm and Term Delivery

At the end of gestation, the cervical tissue changes profoundly. As a result of these changes, the uterine cervix becomes soft and vulnerable to dilation. The process occurring in the cervical tissue can be described as cervical ripening. The ripening is a process derivative of enzymatic breakdown and inflammatory response. Therefore, it is apparent that cervical remodeling is a derivative of the reactions mediated by multiple factors such as hormones, prostaglandins, nitric oxide, and inflammatory cytokines. However, despite the research carried out over the years, the cellular pathways responsible for regulating this process are still poorly understood. A comprehensive understanding of the entire process of cervical ripening seems crucial in the context of labor induction. Greater knowledge could provide us with the means to help women who suffer from dysfunctional labor. The overall objective of this review is to present the current understanding of cervical ripening in terms of molecular regulation and cell signaling.

Addition of vaginal isosorbide mononitrate for labor induction in pregnancies complicated by hypertensive diseases of pregnancy: a randomized controlled trial

BACKGROUND

Pregnancies complicated by hypertensive disease of pregnancy often require labor induction. Rates of cesarean delivery range from 15% to 60% in this population. Nitric oxide deficiency has been shown to underlay the pathophysiology of preeclampsia, and nitric oxide promotes cervical ripening.

OBJECTIVE

We hypothesized that addition of vaginal isosorbide mononitrate for labor induction could decrease the rate of cesarean delivery in pregnancies with hypertensive disease of pregnancy.

STUDY DESIGN

This study was a double-blind, placebo-controlled, randomized trial of patients with singleton pregnancy at ≥24 weeks' gestation undergoing labor induction for hypertensive diseases of pregnancy between November 2017 and February 2020. Participants were eligible if their Bishop score was <6 and if their cervical dilation was ≤2 cm. In addition, participants received up to 3 doses of 40 mg isosorbide mononitrate in addition to misoprostol for labor induction. Labor management was per healthcare provider preference. The primary outcome was rate of cesarean delivery. Secondary outcomes included the length of labor and frequency of intrapartum adverse events, including the use of intrapartum antihypertensive agents.

RESULTS

89 women were randomized to the isosorbide mononitrate group, and 87 women were randomized to the placebo group. Cesarean delivery rates were similar in both groups (32.6% vs 25.3%; relative risk, 1.29; 95% confidence interval, 0.81-2.06; P=.39). Maternal headache was increased in patients exposed to isosorbide mononitrate (42.7% vs 31%; relative risk, 1.52; 95% confidence interval, 1.04-2.23; P=.04). Clinical chorioamnionitis was increased in the placebo group (0% vs 8%; P=.02). Secondary outcomes were similar between groups.

CONCLUSION

The addition of vaginal isosorbide mononitrate for labor induction in pregnancies complicated by hypertensive disease of pregnancy did not result in fewer cesarean deliveries.

A randomized controlled trial comparing isosorbide dinitrate-oxytocin versus misoprostol-oxytocin at management of foetal intrauterine death

Background

The metabolic activity of endogenous nitric oxide (NO) and the medical use of nitrovasodilatory drugs like isosorbide dinitrate have been shown to be potential inducers inducers of cervical ripening prior to surgical evacuation of the uterus.

Objective

To assess the therapeutic efficacy and safety of combined isosorbide dinitrate-oxytocin in the management of intrauterine foetal death (IUFD).

Methods

Sixty women with IUFD after 20 weeks of gestation requesting uterine evacuation were randomly selected to receive isosorbide dinitrate gel solution (80 mg/1.5 mL; n = 30) or misoprostol gel solution (100 mcg/1.5 mL; n = 30) every 3 h with a maximum of four doses or until a Bishop score >7 was reached. Subsequently, patients received a high dose of intravenous oxytocin until complete uterus evacuation was achieved. Therapeutic efficacy was evaluated by mean the relative risk of the foetal expulsion based on comparison of event rates, and the proportion of women induced to labor at 7, 10 and 15 h after the administration of isosorbide dinitrate or misoprostol. Safety was assessed on the basis of woman´s vital signs and evaluation of adverse effects, including headache, abdominal pain, pelvic pain, lower back pain, nausea, dizziness and vomiting.

Results

The foetal expulsion rate using the isosorbide dinitrate-oxytocin combination was approximately 4.4 times, and at least 2.1 times, the foetal expulsion rate with the misoprostol-oxytocin regimen at any given point in time. The proportion of women achieved vaginal delivery at 15 hours was 100% for the isosorbide dinitrate-oxytocin group and 86.7% for the misoprostol-oxytocin group. The average delivery induction interval was significantly lower when isosorbide dinitrate-oxytocin was used (8.7 ± 3.1 h) than when misoprostol-oxytocin (11.9 ± 3.1 h) was used. A total of 20% of patients in the isosorbide dinitrate-oxytocin group recorded headache, and no cases of uterine tachysystole, haemorrhage or coagulopathy were recorded.

Conclusion

This study indicates that intravaginal isosorbide dinitrate followed by intravenous oxytocin was more effective than the conventional method used to induce labour in the medical management of foetal death in pregnancies after 20 weeks of gestation.

Trial registration

Clinicaltrials.gov NCT02488642.

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.

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.

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.

Comparison of isosorbide mononitrate and misoprostol for cervical ripening in termination of pregnancy between 8 and 12 weeks: a randomized controlled trial

AIM

The present study was undertaken to compare the efficacy of isosorbide mononitrate (IMN) and misoprostol for cervical ripening in termination of pregnancy between 8 and 12 weeks.

MATERIALS AND METHODS

This prospective randomized single blind study enrolled 40 women with singleton pregnancy seeking surgical termination of pregnancy between 8 and 12 weeks of gestation. They were divided into two groups--group I received IMN 40 mg while group II received misoprostol 40 mg vaginally, 3 h prior to suction and evacuation. All women were monitored for effects of cervical ripening and adverse effects.

RESULTS

The mean sizes of dilators that could be negotiated without any resistance was 5.9 ± 1.33 in group I and 8.6 ± 0.94 in group II (p < 0.001, 95% CI 0.58, 0.41). The mean dilator sizes at which resistance was first encountered was 6.9 ± 1.37 in group I and 9.9 ± 1.23 in group II (p < 0.001, 95% CI 0.60, 0.54). The mean blood loss was 61.5 ± 13.86 ml in group I and 36.25 ± 12.80 ml in group II (p < 0.001, 95% CI 6.07, 5.63). Headache was the most common adverse effect seen with IMN use.

CONCLUSION

The results show that IMN has a definite role and better safety profile than misoprostol in first trimester cervical ripening, although misoprostol is more effective and causes less blood loss.

Nitric oxide in the human uterine cervix: endogenous ripening factor

The human uterine cervix can produce nitric oxide (NO), a free radical with an ultra-short half-life. The release of NO changes during pregnancy and is increased in early nonviable pregnancies compared to normal uncomplicated pregnancies. This review concentrates on the role of NO release in cervical ripening in pregnant women. Also some suggestions on future aspects are discussed.

Nitric oxide donor isosorbide mononitrate for pre-induction cervical ripening at 41 weeks' gestation: A randomized controlled trial

OBJECTIVE

Nitric oxide donors have been shown to cause cervical ripening. The aim of this study was to determine whether sustained release isosorbide mononitrate (ISMN-SR) 60 mg administered vaginally is effective for pre induction cervical ripening at 41 weeks' gestation.

METHODS

A double-blind randomised controlled trial was carried out at the University Obstetric Unit, Galle, Sri Lanka for a period of 9 months, commencing 1st August 2003. One hundred and fifty-six consecutive women with uncomplicated singleton pregnancies at 41 weeks' gestation with a modified Bishop Score <5 were allocated by stratified (primip/multip) block randomization to receive either ISMN-SR 60 mg (n = 78) or vitamin C 100 mg (n = 78) vaginally. Modified Bishop Score at 41 weeks + 2 days' gestation and the proportions establishing spontaneous labor or becoming favorable for induction of labor (IOL) by 41 weeks + 2 days' gestation were evaluated in each group.

RESULTS

At the commencement of the study there were no differences between the mean age, parity or modified Bishop Score of the two groups. In the ISMN-SR group, there was a marked increase in the proportion establishing spontaneous labor (28% vs 7.5%, P < 0.01) and being favorable for IOL (40% vs 9% P < 0.001), 2 days after therapy. In the ISMN-SR group, there was a significantly higher increase in the mean modified Bishop Score (3.8, 95% CI 2.3-5.3 vs 1.3, 95% CI 0.3-2.2, P < 0.01) and a marked decrease in the proportion of subjects requiring further ripening of the cervix with a Foley catheter. (32% vs 79%, P < 0.001). The cesarean section rates were similar in both groups.

CONCLUSION

Sustained release ISMN administered vaginally is effective for preinduction cervical ripening.

Inflammatory pathways in the mechanism of parturition

Increasing evidence suggests that parturition is an inflammatory process. In this brief overview, inflammatory events occurring in association with parturition, and the mechanism by which they may contribute to labour and delivery will be discussed. Mention will be made of how this information may be of use in regulating the timing and the onset of parturition.

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.

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.

Intracervical application of the nitric oxide donor isosorbide dinitrate for induction of cervical ripening: a randomised controlled trial to determine clinical efficacy and safety prior to first trimester surgical evacuation of retained products of conception

OBJECTIVE

To determine the therapeutic efficacy and safety of a nitric oxide (NO) isosorbide dinitrate donor to induce cervical ripening of women with missed abortions before surgical evacuation of the uterus.

DESIGN

A prospective, randomised, double-blind controlled trial.

SETTING

Tertiary referral maternity teaching hospital. Population Sixty women with missed abortions and no cervical dilation.

METHODS

Women requesting surgical evacuation of the uterus were randomly selected to receive endocervical 80 mg/1.5 mL isosorbide dinitrate gel solution (n= 30) or 400 mug/1.5 mL misoprostol gel solution (n= 30) every 3 hours to a maximum of four doses or until reaching cervical ripening. Vital signs and symptoms were recorded at baseline and then every 3 hours until finishing therapy. Adverse events, such as headache, abdominal pain, pelvic pain, backache, nausea and vomiting, were evaluated.

MAIN OUTCOME MEASURES

Probability of reaching cervical ripening >8 mm Hegar dilator; evaluated at 3, 6, 9 and 12 hours after application of isosorbide dinitrate or misoprostol.

RESULTS

The probabilities of induction of cervical ripening by isosorbide dinitrate and misoprostol after four repeated doses at 3-hour intervals were significantly different (P<0.001). Efficacy of therapy after 12 hours was 97% for the isosorbide dinitrate group and 70% for the misoprostol group. Systolic and diastolic blood pressures were lower after administration of isosorbide dinitrate than prostaglandin analogues. The difference in the mean systolic and diastolic blood pressure between treatment groups was greatest at 3 hours, with a difference of 7.7 mmHg (P<0.001) and 5.9 mmHg (P<0.003), respectively. The most frequent side effect associated with isosorbide dinitrate administration was headache, which occurred in 18 out of 30 patients, compared with only 5 out of 30 women in the misoprostol group [relative risk (RR) 2.41, 95% confidence interval (CI) 1.45-4.03, P<0.001). Women treated with misoprostol reported mainly pelvic pain (RR 3.24, 95% CI 1.99-5.27, P<0.001).

CONCLUSIONS

Intracervical administration of 80 mg isosorbide dinitrate in women with missed abortions appears to be effective for cervical ripening prior to surgical evacuation of the uterus. Differences in the incidence of non-serious adverse events are not likely to be clinically significant.

Induction of labor

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

Randomized controlled trial of vaginal misoprostol versus vaginal misoprostol and isosorbide dinitrate for termination of pregnancy at 13-29 weeks

When compared to the use of 12 hourly 200 microg vaginal misoprostol on its own, the addition of a single dose of 5 mg did not significantly increase the abortion or delivery rate in pregnancy termination at 13-29 weeks gestation. All patients were given intravenous syntocinon at 30 mU/min from the first dose of misoprostol onwards.

Three-dimensional power Doppler ultrasound assessment of the cervix for the prediction of successful induction of labor with prostaglandin in prolonged pregnancy

OBJECTIVE

The purpose of this study was to determine whether 3-dimensional (3D) power Doppler ultrasound examination of the cervix can predict the success of labor induction with prostaglandin in prolonged pregnancy.

METHODS

A prospective study was conducted with 36 women undergoing labor induction with prostaglandin at 41 gestational weeks 5 days and later. All 36 women underwent a transvaginal 2-dimensional gray scale ultrasound examination and a 3D power Doppler ultrasound examination of the cervix immediately before a planned post-term checkup. The analyzed variables were length, anterior-posterior diameter, and width of the cervix and any cervical funneling, cervical volume (in cubic centimeters), vascularization index, flow index, vascularization flow index, parity, and Bishop score. Results were compared among women with start of labor at 12 hours or less and more than 12 hours after application of the first prostaglandin suppository and among women who had delivery at 24 hours or less and more than 24 hours after the start of induction.

RESULTS

Sonographically measured cervical length was shorter (mean, 1.8 versus 2.4 cm; P = .04), the Bishop score was higher (median, 5 versus 3; P = .02), and more women were parous (70% versus 37%; P = .05) among women who were in labor within 12 hours than in those who were not. The Bishop score was higher (median, 4 versus 2; P = .03) and more women were parous (69% versus 23%; P = .01) among women who had delivery at 24 hours or less than among those who did not. Cervical volume and the results of the 3D power Doppler ultrasound examination did not differ among women with different outcomes of labor induction.

CONCLUSIONS

In women undergoing induction of labor with prostaglandin at 41 gestational weeks 5 days or later, sonographic cervical length, Bishop score, and parity are related to the success of labor induction, whereas cervical volume and the results of the 3D power Doppler examination are not.

Therapeutic interventions targeting the nitric oxide system: current and potential uses in obstetrics, bone disease and erectile dysfunction

Nitric oxide is involved in a countless number of physiological processes and is known to have cytoprotective as well as cytotoxic effects. Increased knowledge about the multifaceted role of nitric oxide in a variety of disease states has led to the design of multiple treatment strategies involving the nitric oxide system. The current review focuses on recent research advances in the fields of obstetrics, bone disease and erectile dysfunction that have led to current or potential future therapies involving nitric oxide.

Vaginal administration of the nitric oxide donor isosorbide mononitrate for cervical ripening at term: a randomized controlled study

OBJECTIVE

Our aim was to examine the effect of the nitric oxide donor isosorbide mononitrate on the uterine cervix at term and to evaluate possible adverse effects of this treatment.

STUDY DESIGN

Term pregnant women were randomly selected to receive either 40 mg vaginally administered isosorbide mononitrate or placebo 4 hours before elective cesarean section. Cervical status, maternal blood pressure, maternal pulse rate, fetal heart rate, umbilical arterial Doppler indices, and various side effects were examined.

RESULTS

Isosorbide mononitrate induced a significant increase in cervical distensibility. It also caused a significant change in maternal blood pressure and maternal pulse rate. In addition, the frequency of maternal headache and palpitations was significantly higher in the isosorbide mononitrate group versus the placebo group. However, the intensity of these symptoms was moderate.

CONCLUSION

Vaginal administration of 40 mg of isosorbide mononitrate induces cervical ripening at term. Although the majority of women experienced side effects, no serious clinical maternal or fetal adverse effects, resulting in specific medication or emergency cesarean section, were diagnosed.

Nitric oxide metabolites in cervical fluid during pregnancy: further evidence for the role of cervical nitric oxide in cervical ripening

OBJECTIVE

Cervical tissue expresses all the isoenzymes of nitric oxide synthase. We studied the concentrations of nitric oxide metabolites in the cervical fluid in nonpregnant (n = 11) and pregnant women (n = 106).

STUDY DESIGN

Cervical fluid was collected into a Dacron polyester swab, and nitric oxide metabolites were eluted into physiologic saline solution, which was assayed for nitric oxide metabolites with the Griess reaction. The detection limit of the method is 0.2 micromol/L.

RESULTS

Cervical fluid nitric oxide metabolite was detectable in 46% of nonpregnant women (median, <0.2 micromol/L; 95% CI, 0-49), in 63% of women in early pregnancy (median, 11 micromol/L; 95% CI, 0-23) and in 82% of women in late pregnancy (median, 128 micromol/L; 95% CI, 21-276). In late pregnancy, the cervical fluid nitric oxide metabolite level was higher in women with Bishop score of > or =6 (median, 163 micromol/L; 95% CI, 105-276) than in women with Bishop score of <6 (median, 86 micromol/L; 95% CI, 21-99). Cervical fluid nitric oxide metabolite concentration before the onset of labor in parous women (median, 97 micromol/L; 95% CI, 78-283) was higher (P =.008) than that in nulliparous women (median, 28 micromol/L; 95% CI, 0-95). Cervical fluid nitric oxide metabolites before the initiation of labor (median, 33 micromol/L; 95% CI, 0-95) rose to 3.5-fold (median, 115 micromol/L; 95% CI, 78-284) after the commencement of uterine contractions and showed a significant relationship to Bishop score (r = 0.39, P =.01). Cervical fluid nitric oxide metabolite concentrations were not relative to simultaneous plasma nitric oxide metabolite levels (n = 41 women, r = 0.14, P =.41). Rupture of fetal membranes tended to decrease cervical fluid nitric oxide metabolite levels, whereas gentle cervical manipulation elevated it 6.6-fold in 1 minute. The administration of glyceryl trinitrate (0.5 mg, nitric oxide donor) intracervically resulted in a significant rise in the cervical fluid nitric oxide metabolite level in 2 minutes.

CONCLUSION

Cervical fluid nitric oxide metabolite level rises after cervical ripening, nitric oxide donor administration, or cervical manipulation, which supports a role for cervical nitric oxide in cervical ripening.

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

OBJECTIVES

To assess the adverse effects of isosorbide mononitrate (IMN) compared with misoprostol for cervical ripening at term.

METHODS

One hundred and seven women with term pregnancies referred for induction of labor with Bishop scores of 6 or less were randomly allocated to receive either a 40-mg IMN tablet vaginally (n = 55) or 50 microg misoprostol vaginally (n = 52) every 6 h for a maximum of three doses. They were sent to the labor ward for amniotomy or oxytocin if either their Bishop scores were more than 6 or their cervices were not ripe 24 h after the treatment. Adverse effects, progress, and outcomes of labor were assessed.

RESULTS

Isosorbide mononitrate was associated with fewer adverse effects especially uterine tachysystole (0 vs. 19.2%, P < 0.01) and hyperstimulation (0 vs. 15.4%, P < 0.01). The time from start of medication to vaginal delivery in IMN group was significantly longer (25.6 +/- 6.1 vs. 14 +/- 6.9 h, P < 0.01). Oxytocin was needed in 51 women (92%) of the isosorbide mononitrate group and six women (11%) of the misoprostol group (P < 0.001). The cesarean rate was not significantly different between the groups, but the major indications were different: dystocia (45%) in the IMN group vs. persistent non-reassuring fetal heart rate pattern (56%) in the misoprostol group.

CONCLUSIONS

Cervical ripening with IMN resulted in fewer adverse effects, but was less effective than misoprostol.