Nitric oxide as the final metabolic mediator of cervical ripening

Vaginal Progesterone to Prevent Spontaneous Preterm Birth in Women With a Sonographic Short Cervix: The Story of the PREGNANT Trial

The PREGNANT trial was a randomized, placebo-controlled, multicenter trial designed to determine the efficacy and safety of vaginal progesterone (VP) to reduce the risk of birth < 33 weeks and of neonatal complications in women with a sonographic short cervix (10 to 20 mm) in the mid-trimester (19 to 23 6/7 wk). Patients allocated to receive VP had a 45% lower rate of preterm birth (8.9% vs 16.1%; relative risk = 0.55; 95% CI: 0.33-0.92). Neonates born to mothers allocated to VP had a 60% reduction in the rate of respiratory distress syndrome. This article reviews the background, design, execution, interpretation, and impact of the PREGNANT Trial.

Is human labor at term an inflammatory condition?†

Parturition at term in normal pregnancy follows a predictable sequence of events. There is some evidence that a state of inflammation prevails in the reproductive tissues during labor at term, but it is uncertain whether this phenomenon is the initiating signal for parturition. The absence of a clear temporal sequence of inflammatory events prior to labor casts doubt on the concept that normal human labor at term is primarily the result of an inflammatory cascade. This review examines evidence linking parturition and inflammation in order to address whether inflammation is a cause of labor, a consequence of labor, or a separate but related phenomenon. Finally, we identify and suggest ways to reconcile inconsistencies regarding definitions of labor onset in published research, which may contribute to the variability in conclusions regarding the genesis and maintenance of parturition. A more thorough understanding of the processes underlying normal parturition at term may lead to novel insights regarding abnormal labor, including spontaneous preterm labor, preterm premature rupture of the fetal membranes, and dysfunctional labor, and the role of inflammation in each.

Misoprostol plus isosorbide mononitrate versus misoprostol alone for cervical ripening during labor induction: A systematic review and meta-analysis of randomized controlled trials

AIM

To conduct a systematic review and meta-analysis of all randomized controlled trials (RCTs) that examined the maternal and neonatal outcomes of misoprostol+isosorbide mononitrate (ISMN) versus misoprostol alone (control) in promoting cervical ripening during labor induction.

METHODS

We searched five databases from inception until 05-May-2021. We assessed risk of bias of RCTs, meta-analyzed 23 endpoints, and pooled them as mean difference or risk ratio with 95% confidence interval.

RESULTS

Overall, five RCTs met the inclusion criteria, comprising 850 patients (426 and 424 patients were allocated to misoprostol+ISMN and misoprostol group, respectively). Overall, the RCTs had a low risk of bias. Pertaining to maternal delivery-related outcomes, there was no significant difference between both groups regarding the mean interval from drug administration to delivery, rate of vaginal delivery, rate of cesarean section delivery, and rate of need for oxytocin augmentation. Pertaining to maternal drug-related side effects, the rate of maternal headache was significantly higher in disfavor of the misoprostol+ISMN compared with misoprostol alone. However, the rates of maternal nausea, hypotension, flushing, palpitation, dizziness, postpartum hemorrhage, and uterine tachysystole did not differ between both groups. Pertaining to neonatal outcomes, there was no significant difference between both groups regarding rates of NICU admission, meconium-stained amniotic fluid, and Apgar score <7 at five minutes.

CONCLUSION

Compared with misoprostol alone, co-administration of misoprostol+ISMN did not correlate with superior maternal delivery-related outcomes. The rate of maternal headache was significantly higher in disfavor of the misoprostol+ISMN group. There was no significant difference between both groups regarding neonatal endpoints.

Maternal Glycemic Control in Type 1 Diabetes and the Risk for Preterm Birth: A Population-Based Cohort Study

BACKGROUND

Maternal type 1 diabetes (T1D) has been linked to preterm birth and other adverse pregnancy outcomes. How these risks vary with glycated hemoglobin (or hemoglobin A1c [HbA1c]) levels is unclear.

OBJECTIVE

To examine preterm birth risk according to periconceptional HbA1c levels in women with T1D.

DESIGN

Population-based cohort study.

SETTING

Sweden, 2003 to 2014.

PATIENTS

2474 singletons born to women with T1D and 1 165 216 reference infants born to women without diabetes.

MEASUREMENTS

Risk for preterm birth (<37 gestational weeks). Secondary outcomes were neonatal death, large for gestational age, macrosomia, infant birth injury, hypoglycemia, respiratory distress, 5-minute Apgar score less than 7, and stillbirth.

RESULTS

Preterm birth occurred in 552 (22.3%) of 2474 infants born to mothers with T1D versus 54 287 (4.7%) in 1 165 216 infants born to mothers without diabetes. The incidence of preterm birth was 13.2% in women with a periconceptional HbA1c level below 6.5% (adjusted risk ratio [aRR] vs. women without T1D, 2.83 [95% CI, 2.28 to 3.52]), 20.6% in those with a level from 6.5% to less than 7.8% (aRR, 4.22 [CI, 3.74 to 4.75]), 28.3% in those with a level from 7.8% to less than 9.1% (aRR, 5.56 [CI, 4.84 to 6.38]), and 37.5% in those with a level of 9.1% or higher (aRR, 6.91 [CI, 5.85 to 8.17]). The corresponding aRRs for medically indicated preterm birth (n = 320) were 5.26 (CI, 3.83 to 7.22), 7.42 (CI, 6.21 to 8.86), 11.75 (CI, 9.72 to 14.20), and 17.51 (CI, 14.14 to 21.69), respectively. The corresponding aRRs for spontaneous preterm birth (n = 223) were 1.81 (CI, 1.31 to 2.52), 2.86 (CI, 2.38 to 3.44), 2.88 (CI, 2.23 to 3.71), and 2.80 (CI, 1.94 to 4.03), respectively. Increasing HbA1c levels were associated with the study's secondary outcomes: large for gestational age, hypoglycemia, respiratory distress, low Apgar score, neonatal death, and stillbirth.

LIMITATION

Because HbA1c levels were registered annually at routine visits, they were not available for all pregnant women with T1D.

CONCLUSION

The risk for preterm birth was strongly linked to periconceptional HbA1c levels. Women with HbA1c levels consistent with recommended target levels also were at increased risk.

PRIMARY FUNDING SOURCE

Swedish Diabetes Foundation.

Vasorelaxation Caused by Eugenol, Curcumin and Nanocurcumin is Partially Mediated by Activation of Aminoguanidine-sensitive iNOS in the Middle Uterine Artery of Non-pregnant and Pregnant Capra hircus

Natural products like eugenol and curcumin have been reported to control hypertension. The purpose of our study was to examine the role of iNOS in eugenol/curcumin/nanocurcumin–induced vasorelaxation in the middle uterine artery (MUA) obtained from non-pregnant (NP) and pregnant (P) Capra hircus ( Ch). The MUA rings were mounted in an automatic organ bath attached to a powerlab data acquisition system. Vasorelaxation was induced by eugenol/curcumin/nanocurcumin in either the absence or presence of aminoguanidine in phenylephrine precontracted MUA rings. The vasorelaxation response was recorded isometrically by a highly sensitive isometric force transducer automatic organ bath connected to powerlab and analysed using Labchart 7.1.3 software. The maximal vasorelaxation (Rmax) obtained from eugenol, curcumin and nanocurcumin -induced concentration related contractile response elicited in PE- precontracted ED+ MUA rings was 49.5%, 42.6%, and 40.4% in NP, and 79.5%, 55.5%, and 44.1% in P Ch. Aminoguanidine attenuated the Rmax of eugenol, curcumin and nanocurcumin to 28.2%, 28.5%, and 16.4% in MUA of NP, and 57.2%, 57.4%, and 38.0% in MUA of P Ch, respectively. The results demonstrated that vasorelaxation to (i) Eugenol is partly mediated by partial activation of aminoguanidine-sensitive iNOS in the uterine artery and this pathway is augmented in pregnancy, (ii) Nanocurcumin is mediated by activation of aminoguanidine-sensitive iNOS in the uterine artery of NP, but not in P Ch and (iii) Curcumin is mediated by minimal activation of aminoguanidine sensitive iNOS only in the uterine artery of NP, but not in P Ch. In conclusion, eugenol and nanocurcumin possess a greater potential than curcumin in the control of hypertension due to partial activation of iNOS. These nutraceuticals could be useful to improve blood flow to the uterus to maintain oestrus cycle, maternal and fetal health.

Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data

BACKGROUND

The efficacy of vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix has been questioned after publication of the OPPTIMUM study.

OBJECTIVE

To determine whether vaginal progesterone prevents preterm birth and improves perinatal outcomes in asymptomatic women with a singleton gestation and a midtrimester sonographic short cervix.

STUDY DESIGN

We searched MEDLINE, EMBASE, LILACS, and CINAHL (from their inception to September 2017); Cochrane databases; bibliographies; and conference proceedings for randomized controlled trials comparing vaginal progesterone vs placebo/no treatment in women with a singleton gestation and a midtrimester sonographic cervical length ≤25 mm. This was a systematic review and meta-analysis of individual patient data. The primary outcome was preterm birth <33 weeks of gestation. Secondary outcomes included adverse perinatal outcomes and neurodevelopmental and health outcomes at 2 years of age. Individual patient data were analyzed using a 2-stage approach. Pooled relative risks with 95% confidence intervals were calculated. Quality of evidence was assessed using the GRADE methodology.

RESULTS

Data were available from 974 women (498 allocated to vaginal progesterone, 476 allocated to placebo) with a cervical length ≤25 mm participating in 5 high-quality trials. Vaginal progesterone was associated with a significant reduction in the risk of preterm birth <33 weeks of gestation (relative risk, 0.62; 95% confidence interval, 0.47-0.81; P = .0006; high-quality evidence). Moreover, vaginal progesterone significantly decreased the risk of preterm birth <36, <35, <34, <32, <30, and <28 weeks of gestation; spontaneous preterm birth <33 and <34 weeks of gestation; respiratory distress syndrome; composite neonatal morbidity and mortality; birthweight <1500 and <2500 g; and admission to the neonatal intensive care unit (relative risks from 0.47-0.82; high-quality evidence for all). There were 7 (1.4%) neonatal deaths in the vaginal progesterone group and 15 (3.2%) in the placebo group (relative risk, 0.44; 95% confidence interval, 0.18-1.07; P = .07; low-quality evidence). Maternal adverse events, congenital anomalies, and adverse neurodevelopmental and health outcomes at 2 years of age did not differ between groups.

CONCLUSION

Vaginal progesterone decreases the risk of preterm birth and improves perinatal outcomes in singleton gestations with a midtrimester sonographic short cervix, without any demonstrable deleterious effects on childhood neurodevelopment.

Mifepristone vs balloon catheter for labor induction in previous cesarean: a randomized controlled trial

OBJECTIVE

To compare oral mifepristone (400 mg) with trans-cervical balloon catheter for induction of labor (IOL) in post date women with previous one cesarean section (CS).

METHODS

In this randomized trial, post date pregnant women (gestation 40 weeks 5 days), with previous one low segment CS (no previous vaginal delivery) were induced either with oral mifepristone (400 mg) or balloon catheter [Foley's catheter (16 Fr); bulb filled with 30 ml normal saline]. They were re-assessed 24 and 48 h later. If at any time Bishop Score was >6; amniotomy was done, followed by oxytocin infusion. Primary outcome of the study was labor onset after first manoeuvre. Secondary outcomes were cervical ripening, need of oxytocin, vaginal delivery and CS, in two groups.

RESULTS

From June 2012 to September 2015, we enrolled 107 women. Out of these, 57 received oral tablet mifepristone (400 mg) and 50 were inserted with balloon catheter. Labor onset after first manoeuvre was statistically significantly more in mifepristone group (37/57 vs. 13/50, respectively; p value 0.000). Bishop Score after 24 h was better in balloon catheter (p value 0.000). More women with balloon catheter required oxytocin for IOL (37/50 vs. 20/57, respectively; p value 0.000) along with higher dose [840 (320) mU vs 560 (120) mU, respectively, p value 0.000]. Failure of induction was statistically significantly higher in balloon catheter group (8 out of 50 vs. 2 out of 57, respectively, p value 0.043). There was no statistically significant difference in normal delivery or CS in either group (p value 0.242 and 0.331, respectively).

CONCLUSION

Oral mifepristone (400 mg) is associated with statistically significantly higher incidence of labor onset in post date pregnant women with previous one CS, as compared to balloon catheter. Both methods are primarily for cervical ripening and oxytocin should not be delayed in the absence of onset of labor.

CLINICAL TRIAL REGISTRATION

Clinical Trials Registry-India, www.ctri.nic.in , CTRI/2012/05/003634.

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.

Changes in Cervical Nitric Oxide Concentration Correlate With Bishop Score and Cervical Length Modifications in Prostaglandin E2-Mediated Induction of Labor

OBJECTIVE

Nitric oxide (NO) plays a fundamental role in cervical ripening and it is synthesized in the human cervix. We studied the effect of the dinoprostone on cervical NO release in pregnant women, and we investigated the relationship between cervical NO metabolites, cervical length, and Bishop score.

METHODS

Seventy-seven women underwent induction of labor at > or = 37 weeks of gestation, due to post-term pregnancy (23.8%), oligohydramnios (36.3) or preeclampsia (29.9%). Cervical fluid samples for NO metabolites (NOx), Bishop score, and cervical length were assessed immediately before (time 0 [T0]) and 6 hours after (T6) the local application of dinoprostone, a commercially available prostaglandin E2 (PGE2) analog.

RESULTS

The mean patients' age was 34 +/- 3.2 years, mean gestational age at enrollment was 284 +/- 9.2 days, and nulliparous represented 31.2% of the study population. At time 0, Bishop score was less than 4 in 74% (57/77) of the subjects, mean cervical length was 28.6 +/- 5.8 mm, mean NOx concentration was 208.6 +/- 103.8 microM/mL; 6 hours later, at T6, the mean cervical length decreased to 19.5 +/- 8.8 mm, and the mean NOx concentration increased up to 316.7 +/- 240.9 microM/mL. Data were unaffected by parity or by regular uterine contraction patterns. A statistically significant positive correlation was found between changes in cervical NOx levels and Bishop score modification (P < .01; r = .494), as well as between the modification of NO metabolites concentration and cervical shortening (P < .01; r = .307).

CONCLUSIONS

Prostaglandin (PG)-induced cervical ripening is associated with local NO release. NO plays an active role in cervical remodeling since it positively correlates with both cervical shortening and Bishop score increase. NO oxide and PG are the two pathways that, cross activating each other, trigger the cascade of events responsible of cervical ripening.

Leukocyte Density and Proinflammatory Mediator Expression in Regional Human Fetal Membranes and Decidua Before and During Labot at Term

OBJECTIVES

The region of fetal membranes overlying the cervix, known as the zone of altered morphology (ZAM), is considered to be the principle site of membrane inflammatory activity and extracellular matrix remodelling. We wished to quantify the relative contribution of each area of fetal membranes to the inflammatory process of parturition. Specifically, we aimed to quantify and compare (1) leukocyte densities in three regions of fetal membranes and decidua before and during spontaneous labor at term, and (2) mRNA expression of interleukin (IL)-1beta, IL-6, IL-8, cyclo-oxygenase type 1 (COX-1), and COX-2 in three regions of fetal membranes and decidua before and during spontaneous labor at term.

METHODS

Biopsies of fetal membranes and decidua were obtained from pregnant women delivered by cesarean section at term both before and during spontaneous labor (n = 8 both groups). Fetal membranes were sampled from three areas, the ZAM, midzone (MZ), and periplacental (PP) regions. Leukocytes were identified by immunohistochemistry and their density quantified. Inflammatory mediator expression was quantified using TaqMan technology (Applied Biosystems, Foster City, CA).

RESULTS

There was a significantly greater density of leukocytes in (1) the PP region of membranes compared with the ZAM, and (2) the decidua compared with amnion, amniotic connective tissue, and chorion. IL-1beta, IL-6, and IL-8 mRNA expression was significantly greater in all regions following spontaneous labor compared with nonlaboring tissues. There were no regional differences in cytokine expression within the fetal membranes. Choriodecidua expressed significantly more IL-1beta mRNA than amnion. Amnion expressed more COX-2 mRNA than choriodecidua.

CONCLUSIONS

All regions of fetal membranes and decidua contribute to the inflammatory process of human parturition; however, their relative contributions differ in magnitude. Although the ZAM may be specifically important for membrane rupture, it does not appear to play a key or exclusive role in the other inflammatory processes of parturition. When studying fetal membranes, it is relevant to identify and define the area sampled for consistency and comparison with other studies.

A Retrospective Case-Control Study Evaluating the Role of Mifepristone for Induction of Labor in Women with Previous Cesarean Section

OBJECTIVE

To investigate the role of "mifepristone" for induction of labor (IOL) in pregnant women with prior cesarean section (CS).

METHODS

In this retrospective study, all pregnant women with prior CS who received oral mifepristone (400 mg) for IOL (as per clear obstetric indications) [group 1] were compared with pregnant women with prior CS who had spontaneous onset of labor (SOL) [group 2], with respect to incidence of vaginal delivery, CS, duration of labor, and various maternal and fetal outcomes.

RESULTS

During the study period, 72 women received mifepristone (group 1) for IOL and 346 had SOL (group 2). In group 1 after mifepristone administration, 40 (55.6 %) women had labor onset, and 24 (33.3 %) women had cervical ripening (Bishop Score ≥ 8) within 48 h. There were no statistically significant differences with respect to duration of labor (p value: 0.681), mode of delivery (i.e., normal delivery or CS-p value: 0.076 or 0.120, respectively), or maternal (blood loss or scar dehiscence/rupture uterus), or fetal outcomes (NICU admission) compared to women with previous CS with SOL (group 2). However, the need of oxytocin (p value 0.020) and dose of oxytocin requirement (p value 0.008) were more statistically significant in group 1.

CONCLUSION

Mifepristone may be considered as an agent for IOL in women with prior CS.

Direct electrical stimulation softens the cervix in pregnant and nonpregnant rats

OBJECTIVE

The objective of the study was to determine the effects of electrical stimulation (ES) on cervical ripening in pregnant and nonpregnant rats.

STUDY DESIGN

Timed pregnant and nonpregnant Sprague-Dawley rats (n = 6-7/group) were used. Cervical ES for pregnant rats was performed in vivo on day 15 of gestation by inserting an electrical probe into the vagina in contact with the cervix. Parameters of ES varied from 0.1 to 0.2 mA, 10 pulses per second, 20 milliseconds pulse duration, and repeating pulses for 15, 30, 60, and 120 minutes for pregnant ES groups and similar times for sham control groups with electrode but without ES. Nonpregnant ES groups were stimulated with only 0.2 mA for 30 minutes. Cervical collagen was measured in controls and following ES at various times using light-induced fluorescence (LIF) of collagen. Photographs were taken following ES, and some rats were killed, the cervices were isolated, and cervical extensibility was estimated.

RESULTS

LIF values of pregnant rats are significantly lower (P < .001) and extensibility greater (P < .05) in the ES treatment groups compared with the control groups on days 16 and 17 of pregnancy. Similarly LIF is lower (P < .05) and extensibility values greater (P < .05) in nonpregnant rats treated with ES. No adverse effects, including altered delivery time, pup weights, or damage to cervix, were produced by low current levels of ES needed to soften the cervix.

CONCLUSION

The following conclusions were reached: (1) application of ES rapidly produces softening and ripening of the cervix in pregnant and nonpregnant rats; (2) ES treatment does not produce early delivery; (3) the exact mechanism for ES ripening is not yet known; and (4) ES might be used clinically to ripen the cervix when needed.

Outpatient cervical ripening by nitric oxide donors for prolonged pregnancy: a randomized controlled trial

OBJECTIVE

To assess whether outpatient cervical ripening at 41 0/7 weeks of gestation with the nitric oxide donor isosorbide mononitrate reduces cesarean delivery rates in nulliparous women with an unfavorable cervix.

METHODS

We recruited nulliparous pregnant women with a Bishop score less than 6 in a randomized, multicenter, double-blind, placebo-controlled trial. Women received 40 mg vaginal isosorbide mononitrate or a placebo at 41 0/7, 41 2/7, and 41 4/7 weeks of gestation. They returned home between visits. At 41 5/7 weeks of gestation, for women who had not yet given birth, labor was induced with oxytocin or prostaglandins, depending on cervical status. We needed 685 women per group to detect a 25% reduction in the cesarean delivery rate, the primary outcome measure, from 25% in the placebo group to 18.75% in the isosorbide mononitrate group (1-β=0.8, α=0.05, two-sided).

RESULTS

The NOCETER (NO donors for reduction of CEsareans at TERm) trial was a negative study. The cesarean delivery rate was 27.3% (185/678) in the isosorbide mononitrate group and 27.2% (186/684) in the placebo group (relative risk 1.00, 95% confidence interval [CI] 0.84-1.19). None of the maternal secondary efficacy outcomes differed between groups. Side effects were more common among women receiving isosorbide mononitrate than in the placebo group (78.8% [534/678] compared with 27.9% [191/684], relative risk 2.82, 95% CI 2.49-3.20). Composite perinatal morbidity did not differ between groups.

CONCLUSION

Outpatient cervical ripening with vaginal isosorbide mononitrate for prolonged pregnancy in nulliparous women does not reduce cesarean delivery rate.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00930618.

Amniotic fluid "sludge" is an independent risk factor for preterm delivery

OBJECTIVE

To determine the prevalence and the clinical significance of amniotic fluid "sludge" (AFS) in asymptomatic patients at low and high risk for spontaneous preterm delivery.

METHOD

A prospective cohort study was conducted on 195 singleton pregnancies at low or high risk for preterm birth (PTB) between the 16th and 26th weeks. Cervical length (CL) <25 mm and the presence of AFS were evaluated. The risk for preterm delivery before 28, 32, 35 and 37 weeks were determined according to the presence of AFS, CL < 25 mm and history of high risk for PTB. Stepwise logistic regression was performed to compare variables.

RESULTS

AFS was an independent risk factor for PTB < 35 weeks (OR: 3.08, 95% CI: 1.13-8.34, p = 0.027) but not for PTB < 28, 32 and 37 weeks. CL < 25 mm was an independent risk factor for PTB < 28, 32 and 35 but not for PTB < 37 weeks. High risk for PTB was not found as an independent risk factor for PTB.

CONCLUSION

AFS is an independent risk factor for PTB before 35 weeks.

Cell-specific expression and immunolocalization of nitric oxide synthase isoforms and soluble guanylyl cyclase α and β subunits in postnatal porcine uteri

The aim of the present study was to investigate the cellular expression and immunolocalization of nitric oxide synthase (NOS) isoforms and soluble guanylyl cyclase (sGC) subunits in postnatal porcine uteri. Immunohistochemical experiments showed that three isoforms of NOS were mainly localized in the uterine luminal and glandular epithelium and myometrium, and the intensity of immunostaining for iNOS and eNOS was increased gradually with temporal development of the postnatal uterus. In addition, sGC subunits, sGCα1 and β, were present in the uterine luminal and glandular epithelium, myometrium and stromal cells. The uterine NOS activity data showed that the total NOS and iNOS activities were significantly increased at postnatal days 21 and 35. Although constitutive NOS activity was increased at postnatal day 21, it decreased subsequently at postnatal day 35. Immunoblot analysis revealed that iNOS protein expression was significantly increased at postnatal days 21 and 35. Furthermore, sGCα1 protein expression was not significantly changed throughout days 7 to 35. Collectively, our findings suggest that NO/cGMP signaling is involved in the process of postnatal porcine uterine development.

Inhibitory effect of progesterone on cervical tissue formation in a three-dimensional culture system with human cervical fibroblasts

Progesterone supplementation is recommended to prevent preterm birth in women with a short cervix, but the mechanism is unclear. We hypothesize that progesterone acts by altering the composition of the cervical extracellular matrix (ECM). We tested this hypothesis using human cervical fibroblasts in both two-dimensional (2D) and three-dimensional (3D) cultures. For 2D culture, cells were seeded in 6-well plates and cultured with media supplemented with estradiol (10(-8) M), progesterone (10(-7) or 10(-6) M), and vehicle. For 3D culture, the cells were cultured on a porous silk protein scaffold system. Progesterone and estrogen receptors were documented by immunohistochemistry and Western blot analysis. In both 2D and 3D cultures, decreased collagen synthesis was seen with increased progesterone concentration. Three-dimensional cultures could be maintained significantly longer than 2D cultures, and the morphology of 3D cultures appeared similar to native cervical tissue. Thus, further studies were performed in 3D culture. To determine the effect of progesterone concentration, the 3D scaffolds were cultured with estradiol (10(-8) M) and five conditions: vehicle; 10(-9), 10(-8), or 10(-7) M progesterone; or 10(-7) M progesterone plus 10(-6) M mifepristone. The highest progesterone concentration correlated with the least amount of collagen synthesis. Collagen synthesis progressively increased as progesterone concentration decreased. This effect was partially antagonized by mifepristone, suggesting the mechanism is mediated by the progesterone receptor. This hormonally responsive 3D culture system supports the hypothesis that progesterone has a direct effect on remodeling cervical ECM during pregnancy. The 3D culture system could be useful for studying the mechanism of progesterone effects on the cervix.

Inflammation and Neurotransmission of the Vescico-Uterine Space in Cesarean Sections

Collagen IV and laminin play a key role in regulating stiffness, elasticity and flexibility of the vescico-uterine space (VUS) tissue. The neurotensin (NT), the neuropeptide tyrosine (NPY) and the protein gene product 9.5 (PGP 9.5) possessing vasorelaxation and tissue vascularization activities, play key roles in cervical ripening, scar innervations and pain control. We propose that the integrity of these substances in VUS tissue is compromised after Cesarean section (CS), since wound healing disturbances and pelvic pain, as well as pregnancy and delivery complications, are related with lower uterine segment dysfunctions after CS. Therefore, the contents of collagen IV, laminin, NT, NPY and PGP 9.5 nerve fibres from the VUS tissue samples obtained during the first CS and the repeated CS were comparatively studied. VUS specimens were collected from 104 patients during CS and evaluated by immunohistochemistry. Collagen IV and laminin were mostly found in the vascular membrane bounds and their images were quantitatively evaluated by Quantimet Leica analyzer software. Differences of collagen IV, laminin, NT, NPY and PGP 9.5 values in VUS tissue between the first CS and the repeat CS samples were calculated by Student's Mest. Reduced laminin and increased collagen IV values were observed in the VUS scar tissue after the repeated CS in comparison with those of VUS intact tissue obtained during the first CS. Significantly higher values of nerve fibres, containing NT, NPY and PGP 9.5 were registered in intact VUS tissue samples, respectively 5±0.7, 7±0.6 and 5±0.9 CU, than those of VUS scar tissue samples obtained during the repeated CS, respectively 3±0.6,2±0.4 and 3±0.7 CU (p<0.05). The authors observed increased collagen IV and reduced laminin values after the repeated CS which might be the key signs of inflammatory damage of VUS scar tissue by CS. These findings were strengthened by the registration of decreased NT, NPY and PGP 9.5 values in the same samples, which are important neurotransmitters and are responsible for optimal wound healing, pain control and lower uterine segment functions.

Vaginal progesterone in women with an asymptomatic sonographic short cervix in the midtrimester decreases preterm delivery and neonatal morbidity: a systematic review and metaanalysis of individual patient data

OBJECTIVE

To determine whether the use of vaginal progesterone in asymptomatic women with a sonographic short cervix (≤ 25 mm) in the midtrimester reduces the risk of preterm birth and improves neonatal morbidity and mortality.

STUDY DESIGN

Individual patient data metaanalysis of randomized controlled trials.

RESULTS

Five trials of high quality were included with a total of 775 women and 827 infants. Treatment with vaginal progesterone was associated with a significant reduction in the rate of preterm birth <33 weeks (relative risk [RR], 0.58; 95% confidence interval [CI], 0.42-0.80), <35 weeks (RR, 0.69; 95% CI, 0.55-0.88), and <28 weeks (RR, 0.50; 95% CI, 0.30-0.81); respiratory distress syndrome (RR, 0.48; 95% CI, 0.30-0.76); composite neonatal morbidity and mortality (RR, 0.57; 95% CI, 0.40-0.81); birthweight <1500 g (RR, 0.55; 95% CI, 0.38-0.80); admission to neonatal intensive care unit (RR, 0.75; 95% CI, 0.59-0.94); and requirement for mechanical ventilation (RR, 0.66; 95% CI, 0.44-0.98). There were no significant differences between the vaginal progesterone and placebo groups in the rate of adverse maternal events or congenital anomalies.

CONCLUSION

Vaginal progesterone administration to asymptomatic women with a sonographic short cervix reduces the risk of preterm birth and neonatal morbidity and mortality.

High iNOS mRNA and protein localization during late pregnancy suggest a role for nitric oxide in mouse pubic symphysis relaxation

Remodeling and relaxation of the mouse pubic symphysis (PS) are central events in parturition. The mouse PS remodels in a hormone-controlled process that involves the modification of the fibrocartilage into an interpubic ligament (IpL), followed by its relaxation prior to parturition. It is recognized that nitric oxide synthase (NOS) and consequently nitric oxide (NO) generation play important roles in extracellular matrix modification, and may promote cytoskeleton changes that contribute to the remodeling of connective tissue, which precedes the onset of labor. To our knowledge, no studies thus far have investigated inducible nitric oxide synthase (iNOS) expression, protein localization, and NO generation in the mouse PS during pregnancy. In this work, we used a combination of the immunolocalization of iNOS, its relative mRNA expression, and NO production to examine the possible involvement of iNOS in remodeling and relaxation of the mouse IpL during late pregnancy. The presence of iNOS was observed in chondrocytes and fibroblast-like cells in the interpubic tissues. In addition, iNOS mRNA and NO production were higher during preterm labor on Day 19 of pregnancy (D19) than NO production on D18 or in virgin groups. The significant increase in iNOS mRNA expression and NO generation from the partially relaxed IpL at D18 to the completely relaxed IpL at D19 may indicate that NO plays an important role in late pregnancy during relaxation of the mouse IpL.

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.

The cost-effectiveness of outpatient (at home) cervical ripening with isosorbide mononitrate prior to induction of labour

OBJECTIVES

To assess the cost-effectiveness of outpatient (at home) cervical ripening with isosorbide mononitrate (IMN) prior to induction of labour.

DESIGN

Economic evaluation was conducted alongside a randomised placebo controlled trial (the IMOP trial).

SETTING

Large UK maternity hospital.

POPULATION

A total of 350 nulliparous women with a singleton pregnancy, cephalic presentation > or = 37 weeks gestation, requiring cervical ripening prior to induction of labour.

INTERVENTIONS

Isosorbide mononitrate (n = 177) or placebo (n = 173) self-administered vaginally at home at 48, 32 and 16 hours prior to the scheduled time of admission for induction.

RESULTS

Mean health service costs between the period of randomisation and discharge for mother and infant were 1254.86 pound sterling in the IMN group and 1242.88 pound sterling in the placebo group, generating a mean cost difference of 11.98 pound sterling (bootstrap mean cost difference 12.86 pound sterling; 95%CI: -106.79 pound sterling, 129.39 pound sterling) that was not statistically significant (P = 0.842). The incremental cost per hour prevented from hospital admission to delivery was 7.53 pound sterling. At the notional willingness to pay threshold of 100 pound sterling per hour prevented from hospital admission to delivery, the probability that IMN is cost-effective was estimated at 0.67. This translated into a mean net monetary benefit of 98.13 pound sterling for each woman given IMN.

CONCLUSIONS

Although the probability that IMN is cost-effective approaches 0.7 at seemingly low willingness to pay thresholds for an hour prevented from hospital admission to delivery, our results should be viewed in the light of the clinical findings from the IMOP trial.

Influence of pregnancy and labor on the occurrence of nerve fibers expressing the capsaicin receptor TRPV1 in human corpus and cervix uteri

BACKGROUND

Cervical ripening is a prerequisite for a normal obstetrical outcome. This process, including labor, is a painful event that shares features with inflammatory reactions where peripheral nociceptive pathways are involved. The capsaicin and heat receptor TRPV1 is a key molecule in sensory nerves involved in peripheral nociception, but little is known regarding its role in the pregnant uterus. Therefore, the aim of this study was to investigate human corpus and cervix uteri during pregnancy and labor and non-pregnant controls for the presence of TRPV1.

METHODS

We have investigated human uterine corpus and cervix biopsies at term pregnancy and parturition. Biopsies were taken from the upper edge of the hysterotomy during caesarean section at term (n = 8), in labor (n = 8) and from the corresponding area in the non-pregnant uterus after hysterectomy (n = 8). Cervical biopsies were obtained transvaginally from the anterior cervical lip. Serial frozen sections were examined immunohistochemically using specific antibodies to TRPV1 and nerve markers (neurofilaments/peripherin).

RESULTS

In cervix uteri, TRPV1-immunoreactive fibers were scattered throughout the stroma and around blood vessels, and appeared more frequent in the sub-epithelium. Counts of TRPV1-immunoreactive nerve fibers were not significantly different between the three groups. In contrast, few TRPV1-immunoreactive fibers were found in nerve fascicles in the non-pregnant corpus, and none in the pregnant corpus.

CONCLUSION

In this study, TRPV1 innervation in human uterus during pregnancy and labor is shown for the first time. During pregnancy and labor there was an almost complete disappearance of TRPV1 positive nerve fibers in the corpus. However, cervical innervation remained throughout pregnancy and labor. The difference in TRPV1 innervation between the corpus and the cervix is thus very marked. Our data suggest that TRPV1 may be involved in pain mechanisms associated with cervical ripening and labor. Furthermore, these data support the concept that cervix uteri may be the major site from which labor pain emanates. Our findings also support the possibility of developing alternative approaches to treat labor pain.

Clinical use of nitric oxide donors and L-arginine in obstetrics

Nitric oxide (NO) is a free radical that plays a fundamental role in human physiology, being involved in the homeostasis of different functions. In obstetrics this molecule is determinant in the physiology of labor and cervical ripening; it possibly plays a fundamental role in the etiology of preeclampsia and intrauterine growth restriction, and it could also be utilized in view of its ability to induce smooth muscle relaxation. Several clinical trials have ascertained the ability of the topical application of NO donors to promote cervical ripening, and also labor induction. There is much less evidence on the use of NO donors in the vascular complications of pregnancy, either as prophylactics or therapeutic agents. Due to the capacity of NO to promote relaxation of smooth muscle, NO donors have been employed as tocolytics with performance similar to other agents. Moreover, although anecdotal, the experience of sudden uterine relaxation using NO donors in obstetric emergencies remains of great clinical value.

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.

EMG activity of the muscular and stromal layer of the cervix in relation to EMG activity of the myometrium and cervical dilatation in PGF2α induced parturition in the cow

The goal of this study was to quantify and characterize the electromyographic (EMG) activities in the cervical outer muscular layer and in the cervical stromal layer, and to characterize their relationship with myometrial EMG activity and cervical dilatation during PGF2alpha-induced parturition in term pregnant cows. We continuously measured the EMG activity of the uterine myometrium and cervical outer muscular layer as well as the cervical stromal layer in five cows using bipolar electrodes while at the same time measuring changes in the cervical diameter with ultrasound cervimetry. This we did from the moment a prostaglandin analogue was injected until the expulsion of the calf. In contrast to the cervical stromal layer, the cervical outer muscular layer showed distinct EMG activity, which began to increase at about the same time as the EMG activity of the myometrium, i.e. some 12 h before the start of cervical dilatation. However, the rate of this increase was lower than in the myometrium and it was not characterized, like in the myometrium, by an increase in maximum EMG amplitude. Although the cervical outer muscular layer showed contracture and contraction like EMG activity in unison with in the myometrium, it was also characterized by a more irregular EMG activity, which occurred independently from the myometrium. These data suggest that while the outer muscular layer of the cervix may be considered to be a caudal continuation of the myometrium, it also displays activity independently from the myometrium. The physiological relevance of this activity remains to be explored.

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.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

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.

Isosorbide mononitrate induces increased cervical expression of cyclooxygenase-2, but not of cyclooxygenase-1, at term

OBJECTIVE

Prostaglandin and nitric oxide (NO) are both known to be involved in cervical ripening at term. The aim of the study was to investigate if NO has an effect on cervical expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), the two main isoenzymes involved in prostaglandin synthesis, and to localize these enzymes within the cervix.

STUDY DESIGN

Women with an unripe cervix scheduled for elective caesarean section at term were randomly selected to receive vaginally either the NO donor isosorbide mononitrate (IMN) or placebo 4h before surgery. At the operating theatre, cervical tissue specimens were obtained for immunoblotting and immunohistochemistry.

RESULTS

Increased expression of COX-2 was found in specimens exposed to IMN compared to specimens obtained from women in the placebo group. There was no difference in the expression of COX-1. Immunohistochemistry revealed similar localization of the two enzymes in treated and untreated women.

CONCLUSIONS

Vaginal administration of IMN induces increased cervical expression of COX-2, but not of COX-1. This pathway may be of importance in the process of cervical ripening at term.

Misoprostol induces cervical nitric oxide release in pregnant, but not in nonpregnant, women

OBJECTIVE

The cells of the human uterine cervix synthesize nitric oxide, which may be a factor in cervical ripening. We studied the effect of misoprostol on cervical nitric oxide release in nonpregnant and pregnant women.

STUDY DESIGN

Seventy-two nonpregnant (n=15) and pregnant (n=57; 26 in early pregnancy, 31 in late pregnancy) women were treated with either vaginal misoprostol (n=54) or vaginal placebo (n=18). The dose of misoprostol was 400 mug in nonpregnant and early pregnancy group, and 25 mug in late pregnancy group. Serial cervical fluid samples, collected before and up to 3 hours after misoprostol/placebo, were assessed for the concentration of nitric oxide metabolites by means of the Griess reaction.

RESULTS

Placebo had no effect on cervical fluid nitric oxide metabolite level. In 1 to 3 hours, misoprostol induced 4.3- to 5.2-fold elevations in cervical fluid Nox concentrations in early pregnancy (P < .01), and 4.4- to 18.2-fold elevations in late pregnancy (P < .01), but these responses did not differ significantly from each other. Misoprostol had no effect on cervical fluid nitric oxide metabolites in nonpregnant women. There was a trend towards a relationship between cervical nitric oxide stimulation after misoprostol and cervical ripening.

CONCLUSION

Vaginal misoprostol stimulates cervical nitric oxide release in pregnancy. This suggests a joint action of nitric oxide and prostaglandins in cervical ripening.

mRNA expression and localization of bNOS, eNOS and iNOS in human cervix at preterm and term labour

BACKGROUND

Preterm birth is the primary cause of the neonatal mortality and morbidity. There will be no preterm birth without a cervical softening. Nitric oxide (NO) is shown to be a mediator of term cervical ripening. The aim of this study was to investigate mRNA expression of the three isomers of NO synthases (NOS) and to identify them by immunohistochemistry in the human cervix at preterm birth compared to term.

METHODS

The three isomers of NOS--inducible (iNOS), endothelial (eNOS) and neuronal (bNOS)--were investigated in the human cervix. The expression of mRNA was determined using Real-Time Multiplex RT-PCR. The localisation of synthases in the cervical tissue was analysed using immunohistochemistry. Cervical biopsies were obtained from 4 groups of women without clinical signs of infection: preterm (PTL), term labour (TL), preterm not in labour (PTnotL) and term not in labour (TnotL) patients. One-Way ANOVA, Kruskal-Wallis, Student t-test or Mann-Whitney test were applied as appropriate to determine statistically significant differences among the groups.

RESULTS

Patients in preterm labour had significantly (p < 0.01) higher mRNA levels of all the three NOS isomers compared to those in term labour. Women not in labour, irrespective of gestational age, thus with unripe cervices, had significantly lower eNOS mRNA levels compared to those in labour (p < 0.01). Immunoreactivity for all three NO synthases was observed in each examined sample in all groups. The bNOS staining was the most prominent.

CONCLUSION

The mRNA levels were higher in the preterm labour group compared to the women at term labour. The significant increase of the eNOS mRNA expression, from the unripe to the favourable cervical state during labour, may indicate a role of eNOS and supports the role of NO in the cervical ripening process. All the three synthases were identified by immunohistochemistry in all the groups of study.

Intracervical sodium nitroprusside versus vaginal misoprostol in first trimester surgical termination of pregnancy: a randomized double-blinded controlled trial

BACKGROUND

Results from small-scale randomized studies on the effectiveness of different preparations of nitric oxide donors in cervical priming before first trimester termination of pregnancies are not consistent. We compared sodium nitroprusside gel to misoprostol, the standard agent for cervical priming in this randomized double-blinded controlled trial.

METHODS

Two hundred pregnant patients between 8 to 12 weeks admitted for surgical termination of pregnancy were recruited. They were randomized into either 400 microg vaginal misoprostol and intracervical placebo gel, or 10 mg intracervical sodium nitroprusside gel and placebo tablets 3 h before the procedure. The baseline cervical dilatation and cumulative force required to dilate the cervix from 4 to 9 mm were measured with a tonometer. Blood pressure was measured and side effects were assessed.

RESULTS

The cumulative force to dilate the cervix from 4 to 9 mm was significantly higher in the sodium nitroprusside group, and the difference remained when a sub-group analysis was performed according to parity. Baseline cervical dilatation, duration of operation and operative blood loss were all in favour of misoprostol. Transient drop in blood pressure was observed after sodium nitroprusside treatment.

CONCLUSIONS

Intracervical sodium nitroprusside is not as effective as misoprostol in cervical priming.

Changes in the cervical competence in preterm labour

Cervical competence is a key function in normal and abnormal labour. Remodelling of the cervical structure, by reorientation and changes in the integrity of collagen fibres by an alteration in the content of water, proteoglycans and hyaluronic acid, takes place before parturition. Such morphological changes have been associated with the activation of several biochemical pathways, sharing those of an apyretic, proinflammatory reaction, including the inducible isoform of the nitric oxide synthase (NOS). Nitric oxide (NO) is believed to be the final mediator in the mechanisms that allow ripening of the cervix. A reduction of NO activity in the uterus, together with its activation in the cervix, is hypothesised to be a facilitating factor in human parturition. The local application of NO donors in both animals and humans induces ultrastructural changes similar to those occurring during physiological cervical maturation. NO donors have proven to be clinically effective in facilitating first trimester dilation and curettage. Preliminary data also suggest that in women presenting with threatening preterm labour, there is increased activity of NO in the cervix, which is associated with shortening. A complex interaction between cytokines, prostaglandins (PGs) and NO is the key biochemical pathway accounting for the preterm ripening of the cervix.

Oxytocin Modulates Nitric Oxide Generation by Human Fetal Membranes at Term Pregnancy

PROBLEM

Nitric oxide (NO), an important mediator of the inflammatory response, is involved in several reproductive processes including pregnancy and labor. Uterus, placenta and fetal membranes are significant sources of NO. Presently, there is no information on factors regulating NO production by fetal membranes.

METHOD OF STUDY

Human fetal membranes at term gestation were cultured for 24 hr in the presence of oxytocin. The concentrations of NO metabolites nitrites in culture medium were determined by the Griess reaction. The presence of inducible nitric oxide synthase (iNOS) was determined by reverse transcriptase-polymerase chain reaction and Western blot.

RESULTS

Oxytocin increased nitrite release by fetal membranes. Messenger ribonucleic acid iNOS expression was also enhanced by oxytocin. These effects were more marked in tissues obtained after labor than before labor.

CONCLUSIONS

Oxytocin exerts an overall stimulatory effect on NO release by fetal membranes. This action might be of relevance in the biomolecular processes leading to parturition.

Urinary nitric oxide metabolite changes in spontaneous and induced onset active labor

BACKGROUND

The aim of this prospective, randomized study was to investigate the changes in urinary nitric oxide (NO) metabolite between the latent and the active phases of spontaneous and either prostaglandin E(1) (PGE(1)) or prostaglandin E(2) (PGE(2))-induced labors.

METHODS

Eighty-eight singleton pregnant women at 36-41(+) weeks' gestation without signs of fetal distress were enrolled. The first group consisted of 29 pregnant women in whom labor was induced by PGE(1) applied intravaginally. The second group consisted of 29 pregnant women with labor induced by PGE(2) applied intracervically. The third group consisted of 30 women, who had spontaneous active labor. Clinical data of the three groups were assessed as labor progressed.

RESULTS

Urinary nitric oxide/creatinine (U NO/Cr) decreased significantly after the onset of active labor in all three groups (p < 0.005), with the percentage decline of 42.2%, 28.6% and 10.1%, respectively. The magnitude of the difference in decline in U NO/Cr after active labor between the PGE(1)-induced and the spontaneous labor group was significantly reduced (p = 0.0047) after adjustment for potential confounders using the generalized estimating equations test (GEE). The duration of the latent phase was significantly shortened in the PGE(1)-induced group as compared with the spontaneous labor group (p < 0.01).

CONCLUSIONS

Decreased U NO/Cr may facilitate transition from the latent to the active phase either in spontaneous or induced labors. Our results indicate that U NO/Cr can serve as an easily obtained marker for use in controlling myometrial contractility and cervical ripening at the onset of active labor. The nitric oxide system is present in the human uterus and may contribute to uterine quiescence during pregnancy and show down-regulation in U NO/Cr at the initiation of active labor.

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.

Prostaglandins and the myometrium and cervix

Prostaglandins have long been thought to play important roles in the mechanism of parturition. Here we review the involvement of prostaglandins in myometrial and cervical functions with emphasis on human labor and birth. In addition, the cellular sources of prostaglandins as well as their interactions with various other endocrine, paracrine and physical factors, such as oxytocin, corticotropin releasing hormone, nitric oxide, platelet activating factor, cytokines, endothelin and stretch are also addressed together with their potential role in the molecular reorganization of cervical structure associated with labor and delivery. Finally, the premier role of progesterone in pregnancy maintenance and parturition is juxtaposed with the proposed "fine-tuning", modulatory role of prostaglandins and the above listed factors in the regulation of parturition.