The Randomized Nitric Oxide Tocolysis Trial (RNOTT) for the treatment of preterm labor

Evaluation of nitric acid donor, transdermal glycerol trinitrate patches for facilitating cervical ripening: a randomised controlled trial

PURPOSE

To evaluate the efficacy and safety of transdermal glycerol trinitrate skin patches as an additive and effective agent for facilitating cervical ripening for labour induction.

METHODS

This was a double-blinded prospective randomised clinical trial carried out in a major obstetric unit in India. Women who planned for labour induction were randomly allocated for induction either by combined application of glycerol trinitrate skin patches [GTN patch] and intracervical dinoprostone gel or by the gel only. Sample randomisation was done using a stratified block randomisation technique with a sealed envelope. The numbers designating the group allocation sequence were concealed from doctors, research staff, and investigators. Six hourly improvements were assessed in the modified Bishop's score, induction-delivery time interval, the need for oxytocin, maternal side effects and foetal outcomes. Data were analysed using SPSS software.

RESULTS AND DISCUSSION

Recruitment Bishop scores, parity and gestational age were matched in both cases and the control group. The modified Bishop's score was statistically improved in study groups, as evidenced compositely and irrespective of parity. The two groups appeared to have no significant differences regarding other outcomes. The additional application of the GTN patch seems helpful to accelerate the progress of labour but could not yield any favourable labour outcome. The GTN patch does not impose additional feto-maternal adverse effects apart from increased incidences of headaches.

Evidence of Nitric Oxide Impairment During Hypertensive Pregnancies

Hypertensive disorders of pregnancy complicate up to 10% of pregnancies worldwide, and they can be classified into (1) gestational hypertension, (2) preeclampsia, (3) chronic hypertension and (4) chronic hypertension with preeclampsia. Nitric oxide (NO) plays an essential role in the haemodynamic adaptations observed during pregnancy. It has been shown that the nitric oxide pathway's dysfunction during pregnancy is associated with placental- and vascular-related diseases such as hypertensive disorders of pregnancy. This review aims to present a brief definition of hypertensive disorders of pregnancy and physiological maternal cardiovascular adaptations during pregnancy. We also detail how NO signalling is altered in the (a) systemic vasculature, (b) uterine artery/spiral arteries, (c) implantation and (d) placenta of hypertensive disorders during pregnancy. We conclude by summarizing the anti-hypertensive therapy of hypertensive disorders of pregnancy as a specific management strategy.

Tocolytics for delaying preterm birth: a network meta-analysis (0924)

BACKGROUND

Preterm birth is the leading cause of death in newborns and children. Tocolytic drugs aim to delay preterm birth by suppressing uterine contractions to allow time for administration of corticosteroids for fetal lung maturation, magnesium sulphate for neuroprotection, and transport to a facility with appropriate neonatal care facilities. However, there is still uncertainty about their effectiveness and safety.

OBJECTIVES

To estimate relative effectiveness and safety profiles for different classes of tocolytic drugs for delaying preterm birth, and provide rankings of the available drugs.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov (21 April 2021) and reference lists of retrieved studies.

SELECTION CRITERIA

We included all randomised controlled trials assessing effectiveness or adverse effects of tocolytic drugs for delaying preterm birth. We excluded quasi- and non-randomised trials. We evaluated all studies against predefined criteria to judge their trustworthiness.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed the trials for inclusion and risk of bias, and extracted data. We performed pairwise and network meta-analyses, to determine the relative effects and rankings of all available tocolytics. We used GRADE to rate the certainty of the network meta-analysis effect estimates for each tocolytic versus placebo or no treatment.

MAIN RESULTS

This network meta-analysis includes 122 trials (13,697 women) involving six tocolytic classes, combinations of tocolytics, and placebo or no treatment. Most trials included women with threatened preterm birth, singleton pregnancy, from 24 to 34 weeks of gestation. We judged 25 (20%) studies to be at low risk of bias. Overall, certainty in the evidence varied. Relative effects from network meta-analysis suggested that all tocolytics are probably effective in delaying preterm birth compared with placebo or no tocolytic treatment. Betamimetics are possibly effective in delaying preterm birth by 48 hours (risk ratio (RR) 1.12, 95% confidence interval (CI) 1.05 to 1.20; low-certainty evidence), and 7 days (RR 1.14, 95% CI 1.03 to 1.25; low-certainty evidence). COX inhibitors are possibly effective in delaying preterm birth by 48 hours (RR 1.11, 95% CI 1.01 to 1.23; low-certainty evidence). Calcium channel blockers are possibly effective in delaying preterm birth by 48 hours (RR 1.16, 95% CI 1.07 to 1.24; low-certainty evidence), probably effective in delaying preterm birth by 7 days (RR 1.15, 95% CI 1.04 to 1.27; moderate-certainty evidence), and prolong pregnancy by 5 days (0.1 more to 9.2 more; high-certainty evidence). Magnesium sulphate is probably effective in delaying preterm birth by 48 hours (RR 1.12, 95% CI 1.02 to 1.23; moderate-certainty evidence). Oxytocin receptor antagonists are probably effective in delaying preterm birth by 48 hours (RR 1.13, 95% CI 1.05 to 1.22; moderate-certainty evidence), are effective in delaying preterm birth by 7 days (RR 1.18, 95% CI 1.07 to 1.30; high-certainty evidence), and possibly prolong pregnancy by 10 days (95% CI 2.3 more to 16.7 more). Nitric oxide donors are probably effective in delaying preterm birth by 48 hours (RR 1.17, 95% CI 1.05 to 1.31; moderate-certainty evidence), and 7 days (RR 1.18, 95% CI 1.02 to 1.37; moderate-certainty evidence). Combinations of tocolytics are probably effective in delaying preterm birth by 48 hours (RR 1.17, 95% CI 1.07 to 1.27; moderate-certainty evidence), and 7 days (RR 1.19, 95% CI 1.05 to 1.34; moderate-certainty evidence). Nitric oxide donors ranked highest for delaying preterm birth by 48 hours and 7 days, and delay in birth (continuous outcome), followed by calcium channel blockers, oxytocin receptor antagonists and combinations of tocolytics. Betamimetics (RR 14.4, 95% CI 6.11 to 34.1; moderate-certainty evidence), calcium channel blockers (RR 2.96, 95% CI 1.23 to 7.11; moderate-certainty evidence), magnesium sulphate (RR 3.90, 95% CI 1.09 to 13.93; moderate-certainty evidence) and combinations of tocolytics (RR 6.87, 95% CI 2.08 to 22.7; low-certainty evidence) are probably more likely to result in cessation of treatment. Calcium channel blockers possibly reduce the risk of neurodevelopmental morbidity (RR 0.51, 95% CI 0.30 to 0.85; low-certainty evidence), and respiratory morbidity (RR 0.68, 95% CI 0.53 to 0.88; low-certainty evidence), and result in fewer neonates with birthweight less than 2000 g (RR 0.49, 95% CI 0.28 to 0.87; low-certainty evidence). Nitric oxide donors possibly result in neonates with higher birthweight (mean difference (MD) 425.53 g more, 95% CI 224.32 more to 626.74 more; low-certainty evidence), fewer neonates with birthweight less than 2500 g (RR 0.40, 95% CI 0.24 to 0.69; low-certainty evidence), and more advanced gestational age (MD 1.35 weeks more, 95% CI 0.37 more to 2.32 more; low-certainty evidence). Combinations of tocolytics possibly result in fewer neonates with birthweight less than 2500 g (RR 0.74, 95% CI 0.59 to 0.93; low-certainty evidence). In terms of maternal adverse effects, betamimetics probably cause dyspnoea (RR 12.09, 95% CI 4.66 to 31.39; moderate-certainty evidence), palpitations (RR 7.39, 95% CI 3.83 to 14.24; moderate-certainty evidence), vomiting (RR 1.91, 95% CI 1.25 to 2.91; moderate-certainty evidence), possibly headache (RR 1.91, 95% CI 1.07 to 3.42; low-certainty evidence) and tachycardia (RR 3.01, 95% CI 1.17 to 7.71; low-certainty evidence) compared with placebo or no treatment. COX inhibitors possibly cause vomiting (RR 2.54, 95% CI 1.18 to 5.48; low-certainty evidence). Calcium channel blockers (RR 2.59, 95% CI 1.39 to 4.83; low-certainty evidence), and nitric oxide donors probably cause headache (RR 4.20, 95% CI 2.13 to 8.25; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

Compared with placebo or no tocolytic treatment, all tocolytic drug classes that we assessed (betamimetics, calcium channel blockers, magnesium sulphate, oxytocin receptor antagonists, nitric oxide donors) and their combinations were probably or possibly effective in delaying preterm birth for 48 hours, and 7 days. Tocolytic drugs were associated with a range of adverse effects (from minor to potentially severe) compared with placebo or no tocolytic treatment, although betamimetics and combination tocolytics were more likely to result in cessation of treatment. The effects of tocolytic use on neonatal outcomes such as neonatal and perinatal mortality, and on safety outcomes such as maternal and neonatal infection were uncertain.

Implications of Oxidative and Nitrosative Post-Translational Modifications in Therapeutic Strategies against Reperfusion Damage

Post-translational modifications based on redox reactions "switch on-off" the biological activity of different downstream targets, modifying a myriad of processes and providing an efficient mechanism for signaling regulation in physiological and pathological conditions. Such modifications depend on the generation of redox components, such as reactive oxygen species and nitric oxide. Therefore, as the oxidative or nitrosative milieu prevailing in the reperfused heart is determinant for protective signaling, in this review we defined the impact of redox-based post-translational modifications resulting from either oxidative/nitrosative signaling or oxidative/nitrosative stress that occurs during reperfusion damage. The role that cardioprotective conditioning strategies have had to establish that such changes occur at different subcellular levels, particularly in mitochondria, is also presented. Another section is devoted to the possible mechanism of signal delivering of modified proteins. Finally, we discuss the possible efficacy of redox-based therapeutic strategies against reperfusion damage.

Safety and Efficacy of Tocolytics for the Treatment of Spontaneous Preterm Labour

BACKGROUND

Preterm birth is the major cause of perinatal mortality and morbidity worldwide. Attempts to reduce the burden may be proactive using biochemical or biophysical prediction and preventative measures. If these efforts fail, then the approach may have to be reactive using tocolytics to inhibit spontaneous preterm labour.

OBJECTIVE

We have reviewed the evidence concerning the safety and efficacy of various classes of tocolytic agents.

RESULTS

The evidence to support the use of magnesium sulfate or nitric oxide donors as a tocolytic is poor. Compared to placebo or no treatment, there is evidence to support the efficacy of calcium channel blockers (mainly nifedipine), prostaglandin synthetase inhibitors (mainly indomethacin and sulindac), oxytocin receptor antagonists (mainly atosiban) and β2-agonists (mainly ritodrine, terbutaline, salbutamol and fenoterol). Maternal safety concerns have reduced the use of β2-agonists. Fetal safety and gestational age restrictions have largely condemned prostaglandin synthetase inhibitors to second-line therapy. First-line therapy in Europe and other parts of the world outside the USA and Australia is limited to calcium channel blockers and oxytocin receptor antagonists. With respect to efficacy, atosiban and nifedipine are similar, but the robustness of the evidence favours atosiban. With respect to safety, atosiban is clearly the safest tocolytic as there are fetomaternal concerns with nifedipine, particularly in high daily doses.

CONCLUSION

The perfect tocolytic that is uniformly effective and safe does not exist. Cost, licensing and informed consent are considerations involved in the choice. Efforts continue to develop and introduce other or better agents, including novel compounds such as progesterone, PGF2α antagonists and statins.

Fetal fibronectin testing for reducing the risk of preterm birth

BACKGROUND

Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervicovaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help in selecting which women are at significant risk for preterm birth. This is an update of a review first published in 2008.

OBJECTIVES

To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.

SEARCH METHODS

For this update, we searched Cochrane Pregnancy and Childbirth's Trials Register (7 September 2018), ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (7 September 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomized controlled trials of pregnant women screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data, and checked them for accuracy. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We identified 16 trials, of which six were eligible for inclusion. The six included studies randomized 546 women with singleton gestations and threatened preterm labor (PTL) at 23 0/7 to 34 6/7 weeks. A total of 277 women were randomized to knowledge and 269 to no knowledge of FFN. No trials were identified on asymptomatic women or multiple gestations.The risk of bias of included studies was mixed. For selected important outcomes, preterm birth before 37, 34, and 32 weeks, and maternal hospitalization, we graded the quality of the evidence and created a 'Summary of findings' table. For these outcomes, the evidence was graded as mainly low quality due to the imprecision of effect estimates.Management based on knowledge of FFN results may reduce preterm birth before 37 weeks (21.6%) versus controls without such knowledge (29.2%) (risk ratio (RR) 0.72, 95% confidence interval (CI) 0.52 to 1.01; 4 trials; 357 women; low-quality evidence). However, management based on knowledge of FFN results may make little or no difference to preterm birth before 34 (RR 1.09, 95% CI 0.54 to 2.18; 4 trials; 357 women; low-quality evidence) or maternal hospitalization (RR 1.06, 95% CI 0.79 to 1.43; 5 trials; 441 women; low-quality evidence). The evidence for preterm birth before 32 weeks is uncertain because the quality was found to be very low (average RR 0.79, 95% CI 0.16 to 3.96; 4 trials; 357 women; very low-quality evidence).For all other outcomes, for which there were available data (preterm birth less than 28 weeks; gestational age at delivery (weeks); birthweight less than 2500 g; perinatal death; tocolysis; steroids for fetal lung maturity; time to evaluate; respiratory distress syndrome; neonatal intensive care unit (NICU) admission; and NICU days), knowledge of FFN results may make little or no difference to the outcomes.

AUTHORS' CONCLUSIONS

The evidence from this review suggests that management based on knowledge of FFN results may reduce preterm birth before 37 weeks. However, our confidence in this result is limited as the evidence was found to be of low quality. Effects on other substantive outcomes are uncertain due to serious concerns in study design, inconsistency, and imprecision of effect estimates. No trials were identified on asymptomatic women, or multiple gestations.Future studies are needed that include specific populations (e.g. singleton gestations with symptoms of preterm labor), a study group managed with a protocol based on the FFN results, and that report not only maternal but also important perinatal outcomes. Cost-effectiveness analyses are also needed.

Effectiveness of Tocolytic Agents on Prevention of Preterm Delivery, Neonatal Morbidity, and Mortality: Is There a Consensus? A Review of the Literature

Preterm delivery presents the main cause of neonatal morbidity and mortality worldwide. The rate of preterm delivery is 12% to 13% in the United States, of which 29% concerns preterm deliveries before 34 weeks of gestation. Basic parameter of prevention strategy is implementation of tocolytic therapy in cases of threatened preterm labor. Several therapeutic approaches have been proposed, among which betamimetic agonists, calcium channel blockers, magnesium sulfate, oxytocin receptor blockers, nitrates, and prostaglandin inhibitors, whereas new alternatives such as usage of thiocolchicoside have also been reported. This article is one among few that aims to review the comparative effectiveness of various tocolytic agents regarding prevention of preterm delivery, impact on perinatal morbidity and mortality, neonatal health status, and maternal complications. Main conclusions of recent randomized control trials and meta-analyses are summarized to assess about which agents consensus already exists on their effectiveness, which agents should be further studied to achieve conclusions, as well as those that are rather unlikely to have significant tocolytic impact or any other benefit on neonatal outcome.

Glyceryl trinitrate for the treatment of preterm labor

OBJECTIVE

This study was conducted to compare the tocolytic efficacy of glyceryltrinitrate (GTN) with that of magnesium sulfate (MgSO4) and to investigate serum nitric oxide metabolites before and after tocolysis.

MATERIAL AND METHODS

In total, 48 women between 27 and 34 weeks' gestation with threatened preterm labor and intact membranes were randomly allocated to receive either GTN or MgSO4 tocolysis. Main outcome measures included tocolytic efficacy and maternal side effect(s) of the tocolytic agent. Obstetric and neonatal outcomes as well as pretreatment and posttreatment nitric oxide (NO) metabolites were assessed.

RESULTS

Forty-one patients were included into the final analysis. Uterine contraction cessation times were 3.66±1.28 and 6.83±3.47 hours for GTN and MgSO4 groups, respectively. Similarly, maternal side effects were significantly lower in the GTN group than in the MgSO4 group, and no serious maternal side effects were recorded. Serum NO metabolite levels before treatment were significantly lower in the treatment groups than in the controls. Serum nitrite levels were significantly increased after tocolytic treatment both in MgSO4 and GTN groups.

CONCLUSION

GTN effectively delays preterm delivery and reduces neonatal morbidity and mortality with less maternal side effects and seems to be an effective and safe alternative to MgSO4.

Nitric oxide donors for treating preterm labour

BACKGROUND

A number of tocolytics have been advocated for the treatment of threatened preterm labour in order to delay birth. The rationale is that a delay in birth may be associated with improved neonatal morbidity or mortality. Nitric oxide donors, such as nitroglycerin, have been used to relax the uterus. This review addresses their efficacy, adverse effects and influence on neonatal outcome.

OBJECTIVES

To determine whether nitric oxide donors administered in threatened preterm labour are associated with a delay in birth, adverse effects or improved neonatal outcome.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (1 December 2013).

SELECTION CRITERIA

Randomised controlled trials of nitric oxide donors administered for tocolysis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Twelve trials, including a total of 1227 women at risk of preterm labour, contributed data to this updated review. The methodological quality of trials was mixed; trials comparing nitric oxide donors with other types of tocolytics were not blinded and this may have had an impact on findings.Three studies compared nitric oxide donors (glyceryl trinitrate (GTN)) with placebo. There was no significant evidence that nitric oxide donors prolonged pregnancy beyond 48 hours (average risk ratio (RR) 1.19, 95% confidence interval (CI) 0.74 to 1.90, two studies, 186 women), and although for most adverse effects there was no significant difference between groups, women in the active treatment group in one study were at higher risk of experiencing a headache. For infant outcomes there was no significant evidence that nitric oxide donors reduced the risk of neonatal death or serious morbidity (stillbirth RR 0.36, 95% CI 0.01 to 8.59, one study, 153 infants; neonatal death RR 0.43, 95% CI 0.06 to 2.89, two studies, 186 infants). One study, using a composite outcome, reported a reduced risk of serious adverse outcomes for infants in the GTN group which approached statistical significance (RR 0.29, 95% CI 0.08 to 1.00, 153 infants). Overall, these studies were underpowered to identify differences between groups for most outcomes.When nitric oxide donors were compared with other tocolytic drugs there was no significant evidence that nitric oxide donors performed better than other tocolytics (betamimetics, magnesium sulphate, a calcium channel blocker or a combination of tocolytics) in terms of pregnancy prolongation, although nitric oxide donors appeared to be associated with a reduction in most adverse effects, apart from headache. There was no significant difference between groups for infant morbidity or mortality outcomes.

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to support the routine administration of nitric oxide donors in the treatment of threatened preterm labour.

Pharmacogenomics of 17-alpha hydroxyprogesterone caproate for recurrent preterm birth prevention

OBJECTIVE

We hypothesized that genetic variation affects responsiveness to 17-alpha hydroxyprogesterone caproate (17P) for recurrent preterm birth prevention.

STUDY DESIGN

Women of European ancestry with ≥1 spontaneous singleton preterm birth at <34 weeks' gestation who received 17P were recruited prospectively and classified as a 17P responder or nonresponder by the difference in delivery gestational age between 17P-treated and -untreated pregnancies. Samples underwent whole exome sequencing. Coding variants were compared between responders and nonresponders with the use of the Variant Annotation, Analysis, and Search Tool (VAAST), which is a probabilistic search tool for the identification of disease-causing variants, and were compared with a Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway candidate gene list. Genes with the highest VAAST scores were then classified by the online Protein ANalysis THrough Evolutionary Relationships (PANTHER) system into known gene ontology molecular functions and biologic processes. Gene distributions within these classifications were compared with an online reference population to identify over- and under- represented gene sets.

RESULTS

Fifty women (9 nonresponders) were included. Responders delivered 9.2 weeks longer with 17P vs 1.3 weeks' gestation for nonresponders (P < .001). A genome-wide search for genetic differences implicated the NOS1 gene to be the most likely associated gene from among genes on the KEGG candidate gene list (P < .00095). PANTHER analysis revealed several over-represented gene ontology categories that included cell adhesion, cell communication, signal transduction, nitric oxide signal transduction, and receptor activity (all with significant Bonferroni-corrected probability values).

CONCLUSION

We identified sets of over-represented genes in key processes among responders to 17P, which is the first step in the application of pharmacogenomics to preterm birth prevention.

Tocolytics for preterm premature rupture of membranes

BACKGROUND

In women with preterm labor, tocolysis has not been shown to improve perinatal mortality; however, it is often given for 48 hours to allow for the corticosteroid effect for fetal maturation. In women with preterm premature rupture of membranes (PPROM), the use of tocolysis is still controversial. In theory, tocolysis may prolong pregnancy in women with PPROM, thereby allowing for the corticosteroid benefit and reducing the morbidity and mortality associated with prematurity.

OBJECTIVES

To assess the potential benefits and harms of tocolysis in women with preterm premature rupture of membranes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (15 January 2014).

SELECTION CRITERIA

We included pregnant women with singleton pregnancies and PPROM (23 weeks to 36 weeks and six days). We included any tocolytic therapy compared to no tocolytic, placebo, or another tocolytic.

DATA COLLECTION AND ANALYSIS

All review authors assessed the studies for inclusion. We extracted and quality assessed data.

MAIN RESULTS

We included eight studies with a total of 408 women. Seven of the studies compared tocolysis to no tocolysis. One study compared nifedipine to terbutaline. Compared to no tocolysis, tocolysis was not associated with a significant effect on perinatal mortality in women with PPROM (risk ratio (RR) 1.67; 95% confidence interval (CI) 0.85 to 3.29). Tocolysis was associated with longer latency (mean difference (MD) 73.12 hours; 95% CI 20.21 to 126.03; three trials of 198 women) and fewer births within 48 hours (average RR 0.55; 95% CI 0.32 to 0.95; six trials of 354 women; random-effects, Tau² = 0.18, I² = 43%) compared to no tocolysis. However, tocolysis was associated with increased five-minute Apgar of less than seven (RR 6.05; 95% CI 1.65 to 22.23; two trials of 160 women) and increased need for ventilation of the neonate (RR 2.46; 95% CI 1.14 to 5.34; one trial of 81 women). In the subgroup analysis comparing betamimetic to no betamimetics, tocolysis was associated with increased latency and borderline significance for chorioamnionitis. Prophylactic tocolysis with PPROM was associated with increased overall latency, without additional benefits for maternal/neonatal outcomes. For women with PPROM before 34 weeks, there was a significantly increased risk of chorioamnionitis in women who received tocolysis. However, neonatal outcomes were not significantly different. There were no significant differences in maternal/neonatal outcomes in subgroup analyses comparing cox inhibitor versus no tocolysis, calcium channel blocker versus betamimetic, antibiotic, corticosteroid or combined antibiotic/corticosteroid.

AUTHORS' CONCLUSIONS

Our review suggests there is insufficient evidence to support tocolytic therapy for women with PPROM, as there was an increase in maternal chorioamnionitis without significant benefits to the infant. However, studies did not consistently administer latency antibiotics and corticosteroids, both of which are now considered standard of care.

Transdermal nitroglycerin for the treatment of preterm labor: a systematic review and metaanalysis

OBJECTIVE

The purpose of this study was to evaluate the efficacy and safety of transdermal nitroglycerin as a tocolytic agent in women with preterm labor.

STUDY DESIGN

We conducted a systematic review and metaanalysis of randomized controlled trials.

RESULTS

Thirteen studies were included (1302 women) comparing transdermal nitroglycerin vs placebo (2 studies; n = 186); β2-adrenergic receptor agonists (9 studies; n = 1024); nifedipine (1 study; n = 50); and magnesium sulfate (1 study; n = 42). There were no significant differences between transdermal nitroglycerin and placebo for delivery within 48 hours of the initiation of treatment or at <28, <34, or <37 weeks of gestation, adverse neonatal outcomes, and neurodevelopmental status at 24 months of life. Nevertheless, 1 study found a marginally significant reduction in the risk of a composite outcome of major neonatal morbidity and perinatal death (3/74 [4.1%] vs 11/79 [13.9%]; relative risk, 0.29; 95% confidence interval, 0.08-1.00). When compared with β2-adrenergic receptor agonists, transdermal nitroglycerin was associated with a significant reduction in the risk of preterm birth at <34 and <37 weeks of gestation, admission to the neonatal intensive care unit, use of mechanical ventilation, and maternal side effects. There were no significant differences between transdermal nitroglycerin and nifedipine and magnesium sulfate in delivery within 48 hours of treatment and pregnancy prolongation, respectively. Overall, women who received transdermal nitroglycerin had a higher risk of headache.

CONCLUSION

Although transdermal nitroglycerin appears to be more effective than β2-adrenergic receptor agonists, the current evidence does not support its routine use as a tocolytic agent for the treatment of preterm labor. Further double-blind placebo-controlled trials are needed.

Tocolytic therapy for preterm delivery: systematic review and network meta-analysis

OBJECTIVE

To determine the most effective tocolytic agent at delaying delivery.

DESIGN

Systematic review and network meta-analysis.

DATA SOURCES

Cochrane Central Register of Controlled Trials, Medline, Medline In-Process, Embase, and CINAHL up to 17 February 2012.

STUDY SELECTION

Randomised controlled trials of tocolytic therapy in women at risk of preterm delivery.

DATA EXTRACTION

At least two reviewers extracted data on study design, characteristics, number of participants, and outcomes reported (neonatal and maternal). A network meta-analysis was done using a random effects model with drug class effect. Two sensitivity analyses were carried out for the primary outcome; restricted to studies at low risk of bias and restricted to studies excluding women at high risk of preterm delivery (those with multiple gestation and ruptured membranes).

RESULTS

Of the 3263 titles initially identified, 95 randomized controlled trials of tocolytic therapy were reviewed. Compared with placebo, the probability of delivery being delayed by 48 hours was highest with prostaglandin inhibitors (odds ratio 5.39, 95% credible interval 2.14 to 12.34) followed by magnesium sulfate (2.76, 1.58 to 4.94), calcium channel blockers (2.71, 1.17 to 5.91), beta mimetics (2.41, 1.27 to 4.55), and the oxytocin receptor blocker atosiban (2.02, 1.10 to 3.80). No class of tocolytic was significantly superior to placebo in reducing neonatal respiratory distress syndrome. Compared with placebo, side effects requiring a change of medication were significantly higher for beta mimetics (22.68, 7.51 to 73.67), magnesium sulfate (8.15, 2.47 to 27.70), and calcium channel blockers (3.80, 1.02 to 16.92). Prostaglandin inhibitors and calcium channel blockers were the tocolytics with the best probability of being ranked in the top three medication classes for the outcomes of 48 hour delay in delivery, respiratory distress syndrome, neonatal mortality, and maternal side effects (all cause).

CONCLUSIONS

Prostaglandin inhibitors and calcium channel blockers had the highest probability of delaying delivery and improving neonatal and maternal outcomes.

Tocolytics for preterm premature rupture of membranes

BACKGROUND

In women with preterm labor, tocolysis has not been shown to improve perinatal mortality; however, it is often given for 48 hours to allow for the corticosteroid effect for fetal maturation. In women with preterm premature rupture of membranes (PPROM), the use of tocolysis is still controversial. In theory, tocolysis may prolong pregnancy in women with PPROM, thereby allowing for the corticosteroid benefit and reducing the morbidity and mortality associated with prematurity.

OBJECTIVES

To assess the potential benefits and harms of tocolysis in women with preterm premature rupture of membranes.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (6 April 2011), CENTRAL (The Cochrane Library 2011, Issue 1), MEDLINE (1966 to 6 April 2011) and EMBASE (1974 to 6 April 2011).

SELECTION CRITERIA

We included pregnant women with singleton pregnancies and PPROM (23 weeks to 36 weeks and six days). We included any tocolytic therapy compared to no tocolytic, placebo, or another tocolytic.

DATA COLLECTION AND ANALYSIS

All review authors assessed the studies for inclusion. We extracted and quality assessed data.

MAIN RESULTS

We included eight studies with a total of 408 women. Seven of the studies compared tocolysis to no tocolysis. One study compared nifedipine to terbutaline. Compared to no tocolysis, tocolysis was not associated with a significant effect on perinatal mortality in women with PPROM (risk ratio (RR) 1.67; 95% confidence interval (CI) 0.85 to 3.29). Tocolysis was associated with longer latency (mean difference (MD) 73.12 hours; 95% CI 20.21 to 126.03; three trials of 198 women) and fewer births within 48 hours (average RR 0.55; 95% CI 0.32 to 0.95; six trials of 354 women; random-effects, T(2) = 0.18, I(2) = 43%) compared to no tocolysis. However, tocolysis was associated with increased five-minute Apgar of less than seven (RR 6.05; 95% CI 1.65 to 22.23; two trials of 160 women) and increased need for ventilation of the neonate (RR 2.46; 95% CI 1.14 to 5.34; one trial of 81 women). In the subgroup analysis comparing betamimetic to no betamimetics, tocolysis was associated with increased latency and borderline significance for chorioamnionitis. Prophylactic tocolysis with PPROM was associated with increased overall latency, without additional benefits for maternal/neonatal outcomes. For patients with PPROM before 34 weeks, there was a significantly increased risk of chorioamnionitis in women who received tocolysis. However, neonatal outcomes were not significantly different. There were no significant differences in maternal/neonatal outcomes in subgroup analyses comparing cox inhibitor versus no tocolysis, calcium channel blocker versus betamimetic, antibiotic, corticosteroid or combined antibiotic/corticosteroid.

AUTHORS' CONCLUSIONS

Our review suggests there is insufficient evidence to support tocolytic therapy for women with PPROM, as there was an increase in maternal chorioamnionitis without significant benefits to the infant. However, studies did not consistently administer latency antibiotics and corticosteroids, both of which are now considered standard of care.

Drugs acting on the pregnant uterus

In this review we overview the mechanisms responsible for uterine contractility and relaxation. We then use this as the basis for discussing the two major uterotonins, oxytocin and prostaglandins followed by currently available (although often unlicensed) tocolytics; progesterone, magnesium, calcium channel blockers, oxytocin receptor blockers, β-adrenergic receptor agonists, prostaglandin synthesis inhibitors and nitric oxide donors. In this brief review we have concentrated on the most important mechanisms of action and data obtained on human tissue. By focussing on mechanisms, meta-analyses and Cochrane literature reviews, our aim is to provide insight for clinical usefulness, and highlight where further research is required and where the targets may be.

Anaesthesiological considerations on tocolytic and uterotonic therapy in obstetrics

AIM

Significant side effects of tocolytic and uterotonic substances may be of concern to the anaesthesiologist. Recently, new drugs have been introduced having less side effects for both the mother and the neonate.

METHODS

A literature search was undertaken mainly focusing on meta-analyses, to review the possible side effects that might affect the course of anaesthesia and to suggest which precautions should be considered to prevent the occurrence of significant interactions with anaesthetic manipulations and drugs.

RESULTS

Magnesium sulphate has a proven benefit in lowering systolic blood pressure and preventing the occurrence of eclampsia, but not as a tocolytic. beta-adrenergic agonists are being abandoned due to the availability of tocolytic agents causing less side effects. Calcium channel blockers (CCB) are frequently used but can cause major maternal cardiovascular complications. Nitroglycerin seems to be appreciated as an acute tocolytic rather than a routine substance during pre-term labour. Cyclo-oxygenase-2 inhibitors are still under investigation but their tocolytic benefit is questionable mainly due to foetal side effects. Atosiban is considered the first-choice tocolytic. With respect to oxytocic drugs, oxytocine, prostaglandines and methylergometrine may all cause serious side effects especially when combined. The cardiovascular side effects of prostaglandins and methylergometrine can be life-threatening. Both oxytocin and carbetocin have a rather low risk for maternal complications.

CONCLUSION

Atosiban and CCB are at least as effective tocolytic agents as beta-mimetics but have significantly less side effects. Magnesium sulphate can cause neuromuscular blockade, especially when combined with CCB. Concerning oxytocic agents, short-acting oxyctocin and long-acting carbetocin have the least side effects as compared with prostaglandins and methylergometrine.

Tocolytic therapy: a meta-analysis and decision analysis

OBJECTIVE

To determine the optimal first-line tocolytic agent for treatment of premature labor.

METHODS

We performed a quantitative analysis of randomized controlled trials of tocolysis, extracting data on maternal and neonatal outcomes, and pooling rates for each outcome across trials by treatment. Outcomes were delay of delivery for 48 hours, 7 days, and until 37 weeks; adverse effects causing discontinuation of therapy; absence of respiratory distress syndrome; and neonatal survival. We used weighted proportions from a random-effects meta-analysis in a decision model to determine the optimal first-line tocolytic therapy. Sensitivity analysis was performed using the standard errors of the weighted proportions.

RESULTS

Fifty-eight studies satisfied the inclusion criteria. A random-effects meta-analysis showed that all tocolytic agents were superior to placebo or control groups at delaying delivery both for at least 48 hours (53% for placebo compared with 75-93% for tocolytics) and 7 days (39% for placebo compared with 61-78% for tocolytics). No statistically significant differences were found for the other outcomes, including the neonatal outcomes of respiratory distress and neonatal survival. The decision model demonstrated that prostaglandin inhibitors provided the best combination of tolerance and delayed delivery. In a hypothetical cohort of 1,000 women receiving prostaglandin inhibitors, only 80 would deliver within 48 hours, compared with 182 for the next-best treatment.

CONCLUSION

Although all current tocolytic agents were superior to no treatment at delaying delivery for both 48 hours and 7 days, prostaglandin inhibitors were superior to the other agents and may be considered the optimal first-line agent before 32 weeks of gestation to delay delivery.

Fetal fibronectin testing for reducing the risk of preterm birth

BACKGROUND

Fetal fibronectin (FFN) is an extracellular matrix glycoprotein localized at the maternal-fetal interface of the amniotic membranes, between chorion and decidua, where it is concentrated in this area between decidua and trophoblast. In normal conditions, FFN is found at very low levels in cervico-vaginal secretions. Levels greater than or equal to 50 ng/mL at or after 22 weeks have been associated with an increased risk of spontaneous preterm birth. In fact, FFN is one of the best predictors of preterm birth in all populations studied so far, and can help selecting which women are at significant risk for preterm birth.

OBJECTIVES

To assess the effectiveness of management based on knowledge of FFN testing results for preventing preterm birth.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008), MEDLINE (1966 to December 2007) and all references in identified articles.

SELECTION CRITERIA

Randomized controlled trials of pregnant women between the gestational ages of 22 and 34 weeks screened with FFN for risk of preterm birth. Studies included are based exclusively on knowledge of FFN results versus no such knowledge, and we have excluded studies including women with only positive or only negative FFN results.

DATA COLLECTION AND ANALYSIS

All four authors assessed studies for inclusion and quality and extracted data.

MAIN RESULTS

We identified 13 trials, of which five were eligible for inclusion. The five included studies randomized 474 women, of which 235 were randomized to knowledge and 249 to no knowledge of FFN.Preterm birth less than 37 weeks was significantly decreased with management based on knowledge of FFN results (15.6%) versus controls without such knowledge (28.6%; risk ratio 0.54; 95% confidence interval 0.34 to 0.87). All other outcomes for which there were available data (preterm birth at less than 34, 32, or 28 weeks; gestational age at delivery; birthweight less than 2500 grams; perinatal death; maternal hospitalization; tocolysis; steroids for fetal lung maturity; and time to evaluate) were similar in the two groups. No other maternal or neonatal outcome was available for meaningful analysis.

AUTHORS' CONCLUSIONS

Although FFN is commonly used in labor and delivery units to help in the management of women with symptoms of preterm labor, currently there is not sufficient evidence to recommend its use. Since this review found an association between knowledge of FFN results and a lower incidence of preterm birth before 37 weeks, further research should be encouraged.

Stress and preterm labor and birth in Black women

OBJECTIVE

To examine (a) 3 commonly used measures of stress during pregnancy, (b) changes in stress over time to determine when stress is highest, and (c) whether any of the stress measures predict who will deliver preterm in pregnant Black women.

DESIGN

Prospective descriptive study.

SETTING

Perinatal evaluation center and outpatient clinics of a teaching hospital in the northeast.

PARTICIPANTS

Fifty-nine Black women: 39 were recruited in preterm labor from a Perinatal Evaluation Center, and 20 experiencing healthy pregnancies were recruited from the prenatal clinic.

MEASURES

Stress was measured using 2 paper and pencil tests (the Prenatal Distress Questionnaire and the Perceived Stress Scale) and corticotropin-releasing hormone.

RESULTS

There was not a high correlation between stress measures. Stress at 28 weeks as measured by Prenatal Distress Questionnaire and Perceived Stress Scale was at its highest, but corticotropin-releasing hormone increased to 32 weeks and then decreased.

CONCLUSIONS

Perceived stress, prenatal distress, and corticotropin-releasing hormone do not all appear to be measuring the same phenomenon. Screening for stress in Black women at 28 weeks requires further research as perceived stress levels in Black women experiencing preterm labor around 28 weeks differentiated women who delivered preterm infants from Black women who delivered at term.

Nitric oxide detection by DAF (diaminofluorescein) fluorescence in human myometrial tissue

Nitric oxide (NO) is considered to be involved in the modulation of uterine contractility. In the present pilot study, the direct detection of intracellular NO in pregnant human myometrial tissues has been investigated by using the fluorescent indicator 4,5-diaminofluorescein-2 diacetate (DAF-2DA). Pregnant myometrial tissue samples were obtained during Cesarean sections between week 34 and 40 of gestation before the onset of labor. Living explants were loaded with 10 microM DAF-2DA, stimulated with 1 mM arginine, subsequently fixed with glutaraldehyde and examined by fluorescence microscopy. The presence of NO synthases (NOS) was studied by immunohistochemistry. After application of DAF-2DA, DAF fluorescence was located primarily in blood vessels and to a minor extent in myometrial cells. By immunohistochemistry, strong endothelial NOS (eNOS) staining was found in vessel walls. In myometrial cells weak staining of eNOS and inducible NOS was observed. We conclude that the direct NO detection by DAF-2DA provides a new and independent method to identify sites of NO production in myometrium and other heterogeneous tissues.

Effects of oral l-arginine on the pulsatility indices of umbilical artery and middle cerebral artery in preterm labor

OBJECTIVE

The objective of the study was the estimation of the influence of oral supplementation with low-dose l-arginine on feto-placental circulation in women with threatened preterm labor.

STUDY DESIGN

Oral administration of 3g of L-arginine daily or placebo as a supplement to standard tocolytic therapy was tried in 70 women with threatened preterm delivery, randomly assigned to the L-arginine (n=37) or placebo (n=33) groups. Twenty-five and 20 completed the study, respectively. Doppler velocimetry of pulsatility indices (PI) of the umbilical (UA) and middle cerebral (MCA) arteries as well as pregnancy outcome and biochemical markers of nitric oxide synthesis (plasma amino acid and nitrite/nitrate levels, as well as 24 h nitrite/nitrate excretion with urine) were estimated.

RESULTS

Starting from the second week of therapy, the UA PI values were significantly lower in the L-arginine group than in the placebo group. Moreover, treatment with L-arginine caused a significant increase in MCA PI and cerebro-placental ratio (CPR) values. The changes in feto-placental circulation in the L-arginine group were not associated with any signs of increased nitric oxide synthesis.

CONCLUSION

Oral supplementation with low doses of L-arginine changed feto-placental blood flow distribution in patients with threatened preterm labor. The exact mechanism of L-arginine action on feto-placental circulation requires further investigation.

Fetal surgery

Fetal surgery has emerged from the realm of medical curiosity into an exciting, multidisciplinary specialty now capable of improving patient outcomes for a wide variety of diseases. Recent advances allow prenatal providers to both accurately diagnose and treat many fetal anomalies while maintaining maternal safety. As the initial postnatal health care providers to the majority of these newborns, neonatologists need to be familiar with some of the more recent state-of-the-art procedures currently being used. In this review, the authors discuss the prenatal evaluation process and various operative approaches (ie, open hysterotomy, fetoscopy, and percutaneous) to conduct fetal surgery. They then analyze the effectiveness of some of the more established and experimental prenatal therapies that are being performed for a number of fetal anomalies, including twin-twin transfusion syndrome, thoracic malformations, airway obstruction, congenital diaphragmatic hernia, myelomeningocele, and aortic valve stenosis.

The present and future of tocolysis

This chapter discusses the tocolytic agents currently in use for the treatment of preterm labour and considers them in light of the evidence base. These agents are the beta2 sympathomimetic agonists, magnesium sulphate (MgSO(4)), indomethacin, nifedipine and atosiban. The available evidence for these agents shows that the beta2 agents are effective but have significant maternal side effects and no effect on perinatal outcome. MgSO(4) and glyceryl trinitrate are clearly ineffective. Nifedipine is effective with a low maternal side effect profile and is associated with improved perinatal outcomes. Meta-analyses of the several randomized controlled trials of atosiban show that it is no more effective than other tocolytic therapies. Possible directions for the future will be discussed.

The regulation of uterine relaxation

The regulation of uterine relaxation is poorly understood but research in myometrial tissue and other types of smooth muscle has defined a number of receptors, ion channels and regulatory proteins that are likely to be involved. Some of these proteins are substrates for protein kinases, especially cyclic nucleotide dependent kinases. More research is necessary to identify the key molecules involved in the maintenance of uterine quiescence in pregnancy. The use of tocolytics in preterm labour remains controversial; there is a need to identify better pharmacological targets to provoke safe and selective uterine relaxation and improve neonatal outcome.

Randomized double-blind placebo-controlled trial of transdermal nitroglycerin for preterm labor

OBJECTIVE

Despite advances in perinatal medicine, the incidence of preterm birth continues to increase. The primary goal of tocolytic therapy is to reduce neonatal morbidity and mortality. While studies have demonstrated a prolongation of pregnancy, no tocolytic has been shown to improve neonatal outcomes. The objective of this randomized placebo-controlled trial was to determine the effect of transdermal nitroglycerin on neonatal outcomes in women who present in preterm labor.

STUDY DESIGN

We randomized 153 women in labor between 24 and 32 weeks to receive either transdermal nitroglycerin or placebo patches. The primary outcome was a composite of neonatal morbidity (chronic lung disease, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis) and mortality. Secondary outcomes included birth within 48 hours, birth before 28, 34, and 37 weeks, number of doses of antenatal corticosteroids received, side effects, and adverse events.

RESULTS

Infants born to transdermal nitroglycerin treated mothers (n = 74) had a statistically significantly reduced composite outcome compared to placebo treated mothers (n = 79) (relative risk 0.29 [95% confidence interval 0.08, 1.00] [p = 0.048]; risk difference -0.10 [95% confidence interval -0.19, -0.01); number needed to treat 10 [95% confidence interval 5, 100]). Birth prior to 28 weeks was reduced (relative risk 0.50, 95% confidence interval 0.23, 1.09). Transdermal nitroglycerin caused significantly more maternal side effects (relative risk 1.41, 95% confidence interval 1.06, 1.86).

CONCLUSION

Transdermal nitroglycerin may reduce neonatal morbidity and mortality as a result of decreased risk of birth before 28 weeks.

Neonatal neurodevelopmental outcomes following tocolysis with glycerol trinitrate patches

OBJECTIVE

The object of this study was to determine the effects of maternal tocolysis with glycerol trinitrate (GTN) patches on the neurodevelopment of infants.

STUDY DESIGN

This was a randomized, multicenter, controlled trial comparing the efficacy of GTN patches with standard beta2 agonist as tocolytic therapy. The previously reported outcomes of this study indicated no difference in neonatal mortality or morbidity to hospital discharge. One hundred fifty-six surviving infants from 2 Australian centers were psychometrically assessed using the Griffiths Mental development Scales (revised) at 18 months of age.

RESULTS

There was no difference in psychometric performance between those infants enrolled in either the GTN (81 infants) or beta2 agonist (75 infants) arm of the study.

CONCLUSION

This randomized trial supports no significant difference between GTN patches in comparison with standard beta2 agonist for tocolytic therapy. The results underscore the association between premature labor and adverse infant outcomes.

Drug therapy during labor and delivery, part 2

PURPOSE

The drug therapy of common conditions and complications during labor and delivery and the fetal and neonatal effects of this therapy are examined.

SUMMARY

The pharmacologic therapy of common conditions that occur in labor and delivery primarily involves oxytocin and prostaglandins for cervical ripening and labor induction and systemic and regional narcotic analgesics for pain. Because most medications used in women during labor and delivery do not have Food and Drug Administration-approved labeling, pharmacists should understand the benefits and limitations of medications used in the mother. Although induction and augmentation of labor and the control of pain often require drug therapy, other, less frequent, complications may occur in labor. Drug therapies for these complications include anti-infective agents to treat maternal infection and prevent neonatal diseases; antiretrovirals to reduce perinatal HIV-1 transmission from the mother to the fetus; corticosteroids to prevent fetal lung immaturity; antihypertensives to treat preeclampsia; anticonvulsants to treat eclampsia; antibiotics to prolong pregnancy and improve neonatal outcomes after premature rupture of the membranes; tocolytics for premature labor; and oxytocin, ergot alkaloids, and prostaglandin analogues for postpartum hemorrhage. The fetal and neonatal effects of therapy for the conditions that occur during labor and delivery are usually benign, but significant morbidity and mortality involving the mother, the fetus, and the newborn are ever-present risks.

CONCLUSION

Awareness of the conditions and complications requiring drug therapy during labor and delivery will allow hospital pharmacists to make knowledgeable decisions about the rapid accessibility of critical medications in the labor and delivery unit.

beta-Agonist tocolytic therapy

With the advent of preterm birth prevention programs, increasing numbers of patients are now considered candidates for tocolytic management. Tocolysis' chief benefit is significantly prolonging pregnancy in the hope of avoiding or ameliorating the sequelae of preterm delivery. Three principal indications dominate the use of tocolysis in the treatment of preterm labor: (1) prophylaxis, (2) acute therapy, and (3) maintenance.

Nitric oxide donors for the treatment of preterm labour

BACKGROUND

A number of tocolytics have been advocated for the treatment of threatened preterm labour in order to delay delivery. The rationale is that a delay in delivery may be associated with improved neonatal morbidity or mortality. Nitric oxide donors, such as nitroglycerin, have been used to relax the uterus. This review addresses their efficacy, side effects and influence on neonatal outcome.

OBJECTIVES

To determine whether nitric oxide donors administered in threatened preterm labour are associated with a delay in delivery, adverse side effects or improved neonatal outcome.

SEARCH STRATEGY

A comprehensive search of the Cochrane Pregnancy and Childbirth Group trials register (March 2002) and the Cochrane Controlled Trials Register (The Cochrane Library, Issue 1, 2002) was undertaken.

SELECTION CRITERIA

Randomised controlled trials of nitric oxide donors administered for tocolysis.

DATA COLLECTION AND ANALYSIS

Trial quality assessment and data extraction were done independently by two reviewers.

MAIN RESULTS

Five randomised controlled trials (466 women) were included. Nitroglycerine was the NO donor used in all these trials. Nitric oxide donors did not delay delivery nor improve neonatal outcome when compared with placebo, no treatment or alternative tocolytics such as ritodrine, albuterol and magnesium sulphate. There was, however, a reduction in number of deliveries less than 37 weeks when compared with alternative tocolytics but the numbers of deliveries before 32 and 34 weeks were not influenced. Side effects (other than headache) were reduced in women who received nitric oxide donors rather than other tocolytics. However, women were significantly more likely to experience headache when NO donors had been used.

REVIEWER'S CONCLUSIONS

There is currently insufficient evidence to support the routine administration of nitric oxide donors in the treatment of threatened preterm labour.