Randomized comparison of intravenous nitroglycerin and magnesium sulfate for treatment of preterm labor

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.

Prehospital Breech Delivery with Fetal Head Entrapment -A Case Report and Review

We present a case in which an emergency medical services (EMS) crew was called for a precipitous breech delivery with fetal head entrapment that was unrelieved following standard prehospital interventions and eventually resulted in neonatal cardiac arrest and death. Although this is a rare occurrence, EMS responders must have adequate training and guidelines on how to assist with vaginal delivery of breech presentation and how to appropriately manage fetal head entrapment in the field. There is little literature to provide guidance but it appears that standard EMS teaching does not represent current best obstetrical practice. We review the available literature, make expert recommendations, and provide a sample new treatment guideline for basic life support, advanced life support, and EMS physician response.

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.

Magnesium sulfate therapy for the prevention of cerebral palsy in preterm infants: a decision-analytic and economic analysis

OBJECTIVE

We sought to estimate the cost-effectiveness of magnesium neuroprophylaxis for all women at risk for preterm birth <32 weeks.

STUDY DESIGN

A decision analytic and cost-effectiveness model was designed to compare use of magnesium for neuroprophylaxis vs no treatment for women at risk for preterm birth <32 weeks due to preterm premature rupture of membranes or preterm labor from 24-32 weeks. Outcomes included neonatal death and moderate-severe cerebral palsy. Effectiveness was reported in quality-adjusted life years.

RESULTS

Magnesium for neuroprophylaxis led to lower costs ($1739 vs $1917) and better outcomes (56.684 vs 56.678 quality-adjusted life years). However, sensitivity analysis revealed the model to be sensitive to estimates of effect of magnesium on risk of moderate or severe cerebral palsy as well as neonatal death.

CONCLUSION

Based on currently published evidence for efficacy, magnesium for neuroprophylaxis in women at risk to deliver preterm is cost-effective.

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.

A cost decision analysis of 4 tocolytic drugs

OBJECTIVE

The purpose of this study was to determine the optimal tocolytic agent, based on a cost decision analysis.

STUDY DESIGN

A PubMed search of commonly used tocolytics was performed to determine the probability of adverse events. Cost for an agent was determined by acquisition cost and the probability and cost of adverse events. A decision tree was constructed to determine which tocolytic had the lowest total costs, with subsequent sensitivity analysis.

RESULTS

A total of 19 clinical trials combined for a cohort of 1073 patients (indomethacin, 176 patients; magnesium sulfate, 451 patients; nifedipine, 176 patients; and terbutaline, 270 patients). The probability of adverse events was 57.9% for terbutaline, 22.0% for magnesium sulfate, 27.2% for nifedipine, and 11.4% for indomethacin. Nifedipine ($16.75) and indomethacin ($15.40) were the least expensive treatment options, compared with magnesium sulfate ($197.90) and terbutaline ($399.02) because of the cost of monitoring and treating adverse events.

CONCLUSION

If one elects a tocolytic, both nifedipine and indomethacin should be the agents of choice, based on a cost decision analysis.

Randomized comparison of intravenous terbutaline vs nitroglycerin for acute intrapartum fetal resuscitation

OBJECTIVE

The purpose of this study was to compare terbutaline and nitroglycerin for acute intrapartum fetal resuscitation.

STUDY DESIGN

Women between 32-, 42 weeks' gestation were assigned randomly to 250 microg of terbutaline or 400 microg nitroglycerin intravenously for nonreassuring fetal heart rate tracings in labor. The rate of successful acute intrapartum fetal resuscitation and the maternal hemodynamic changes were compared. Assuming a 50% failure rate in the terbutaline arm, we calculated that a total of 110 patients would be required to detect a 50% reduction in failure in the nitroglycerin group (50% to 25%), with an alpha value of .05, a beta value of .20, and a power of 80%.

RESULTS

One hundred ten women had nonreassuring fetal heart rate tracings in labor; 57 women received terbutaline, and 53 women received nitroglycerin. Successful acute resuscitation rates were similar (terbutaline 71.9% and nitroglycerin 64.2%; P = .38). Terbutaline resulted in lower median contraction frequency per 10 minutes (2.9 [25-75 percentile, 1.7- 3.3] vs 4 [25-75 percentile, 2.5- 5]; P < .002) and reduced tachysystole (1.8% vs 18.9%; P = .003). Maternal mean arterial pressures decreased with nitroglycerin (81-76 mm Hg; P = .02), but not terbutaline (82-81 mm Hg; P = .73).

CONCLUSION

Although terbutaline provided more effective tocolysis with less impact on maternal blood pressure, no difference was noted between nitroglycerin and terbutaline in successful acute intrapartum fetal resuscitation.

Magnesium Sulfate: The First-Line Tocolytic

Magnesium sulfate has become the first-line tocolytic for short-term use to arrest idiopathic preterm labor. The reasons for its acceptance include familiarity of the drug, ease of use, and the virtual absence of serious maternal side effects. Sufficient data exist showing its efficacy if used in higher doses. Attention to treating preterm labor has shifted to seeking answers about the fundamental causes. Gathering information about the specific causes and designing tailor-made treatment protocols for each of the numerous potential causes is essential. Scientifically sound research is needed to obtain answers about the important clinical questions surrounding magnesium sulfate.

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

OBJECTIVE

This study was undertaken to assess the effectiveness of glyceryl trinitrate (GTN) patches in comparison with beta2 sympathomimetics (beta2) for the treatment of preterm labor.

STUDY DESIGN

A multicenter, multinational, randomized controlled trial was conducted in tertiary referral teaching hospitals. Women in threatened preterm labor with positive fetal fibronectin or ruptured membranes between 24 and 35 weeks' gestation were recruited and randomly assigned to either beta2 or GTN with rescue beta2 tocolysis if moderate-to-strong contractions persisted at 2 hours. Obstetric and neonatal outcomes were assessed.

RESULTS

Two hundred thirty-eight women were recruited and randomly assigned, 117 to beta2 and 121 to GTN. On a strict intention-to-treat basis, there was no significant difference in the time to delivery using Kaplan-Meier curves (P = .451). At 2 hours, 27% of women receiving beta2 had moderate or stronger contractions compared with 53% in the GTN group (P < .001). This led to 35% of women in the GTN group receiving rescue treatment. If delivery or requirement for beta2 rescue are regarded as treatment failure, then a significant difference was observed between the 2 arms (P = .0032). There were no significant differences in neonatal outcomes.

CONCLUSION

GTN is a less efficacious tocolytic compared with ss2 sympathomimetics.

Évaluation de l'algorithme de prise en charge des appels pour menace d'accouchement prématuré utilisé par la cellule de transfert périnatal de la région Rhône-Alpes

OBJECTIVE

Preterm labor is one of the major causes of concern for level I and II obstetricians. The purpose of this study was to determine the incidence of in utero transfer performed for preterm labor. We also aimed to evaluate the algorithm we used in case of call for preterm labor. This algorithm allowed us to study the rate of endovaginal sonography use prior to in utero transfer, to calculate its predictive value and to evaluate the risk of delivery during transfer.

PATIENTS AND METHOD

We conducted an 8-months prospective study of all calls for preterm labor received at a regional call center in France (EU). All obstetrical data were entered in a computerized anonymous database. Three months after the first call midwives collected data from the receiving hospital.

RESULTS

Calls for preterm labor account for 40% of calls for in utero transfer. Two hundred and sixty-five calls have been received for preterm labor; among them 50 cases were associated with a preterm rupture of membrane, a maternal or fetal pathology and 14 cases were lost for follow-up. Those 64 cases were excluded leaving 201 cases for analysis. Twenty-eight had a cervix dilated 4 cm, or more, while 173 had a cervix dilated less than 4 cm. Fifty percent of woman that had a cervical dilatation of 4 cm or more delivered more than 4 h after the call. Among the 173 patients that had a cervix dilated less than 4 cm, 71% had not delivered 7 days after the hotline call and 26% had an endovaginal ultrasonography performed before the transfer. None of the women that had a cervical length longer than 27 mm delivered in the 7 following days. None of the 176 women that were transferred delivered during the transfer.

DISCUSSION AND CONCLUSION

In utero transfer for preterm labor is the leading cause of in utero transfer. Endovaginal ultrasonography prior to transfer should be performed in order to avoid unnecessary transfer. Women who have a preterm labor with a cervical dilatation of 4 cm or more are not an absolute contra-indication to in utero transfer. In those cases the transfer indication should be discussed on a case-to-case basis including the actual term and the distance between hospitals.

Sublingual nitroglycerin versus intravenous ritodrine as tocolytic for external cephalic version: a double-blinded randomized trial

OBJECTIVE

The purpose of this study was to compare the efficacy of sublingual nitroglycerin with that of intravenous ritodrine as a tocolytic agent for external cephalic version in nulliparous women.

STUDY DESIGN

We performed a double-blinded, randomized trial. Nulliparous patients, between 36 and 40 weeks of gestation, were assigned randomly to receive either (1) an intravenous infusion of ritodrine (111 microg/min) for 20 minutes, followed by two puffs of sublingual placebo or (2) an intravenous infusion of sodium chloride 0.9% (placebo) for 20 minutes, followed by two puffs of sublingual 0.4 mg of nitroglycerin. Three minutes after the administration of the sublingual spray, an external cephalic version was attempted. The rate of successful external cephalic version and side effects was compared between groups.

RESULTS

Of 74 randomly assigned patients, 38 patients received intravenous ritodrine, and 36 patients received sublingual nitroglycerin. Although not statistically significant, the rate of the successful external cephalic version was higher in the ritodrine group compared with the nitroglycerin group (45% vs 25%, P =.075). The rate of headaches was higher in patients who received nitroglycerin (28% vs 8%, P =.02). Mean blood pressure and maternal heart rate were lower in the nitroglycerin group 10 minutes after the administration of the medication. However, there was no significant difference in the rate of palpitations, hypotension, or fetal bradycardia between the two groups.

CONCLUSION

When compared with intravenous ritodrine, sublingual nitroglycerin was associated with a higher rate of headache, lower blood pressure, and a trend toward a lower rate of successful external cephalic version.

Local and systemic tolerability of magnesium sulphate for tocolysis

An open-label, randomised, parallel-group, study was conducted in three study centres in women with premature labor and indication for a single agent intravenous tocolysis therapy with magnesium sulphate. The aim of this study was to examine the local and general tolerability and side-effects of magnesium sulphate for tocolysis. Furthermore, we tested the tolerability of a ready-for-use magnesium solution. No measurements of efficacy were performed during this study. Initially, patients received a loading dose of 4.0 g magnesium sulphate administered over 30 min. Thereafter, a continuous intravenous infusion of 1-2 g magnesium sulphate per hour up to 21 days was given. Venous score (Maddox), vital signs, adverse events as well as general tolerability (assessed by investigator and patients) and blood parameters were assessed. We showed good local and systemic tolerability of high dose magnesium sulphate for tocolysis. Only seven patients (15%) were withdrawn from the study prematurely due to minor adverse events. Potential serious complications of MgSO(4) such as respiratory arrest or clinically relevant respiratory depression were not observed. The most frequently reported local adverse events were injection site pain, itching, erythema, swelling, induration and palpable venous cord. The most common systemic adverse events considered to be possibly related to the study drugs involved the nervous system (dizziness) followed by the digestive system (nausea, constipation). Systolic and diastolic blood pressure changed only slightly during the treatment. Respiratory rate and body temperature remained stable also. Toxic magnesium levels (>2.5 mmol/l) were not observed. The assessment of the clinical investigators with regard to tolerability was very good or good in 72.5% of the patients. The introduction of the ready-to-use solution has the advantage of eliminating the need to mix the solution prior to administration. This means a lower risk of overdose and contamination.

Magnesium sulphate for preventing preterm birth in threatened preterm labour

BACKGROUND

Magnesium sulphate is used to inhibit uterine activity in women in preterm labour to prevent preterm birth.

OBJECTIVES

To assess the effectiveness and safety of magnesium sulphate therapy given to women in threatened preterm labour with the aim of preventing preterm birth and its sequelae.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (May 2002) and the Cochrane Controlled Trials Register (The Cochrane Library, Issue 2, 2002).

TYPES OF PARTICIPANTS

Women thought to be in preterm labour. Types of interventions: Magnesium sulphate as the only tocolytic, administered intravenously or orally, compared with either placebo, no treatment or alternative tocolytic therapy. Types of outcome measures: Measures of effectiveness, complications, women's satisfaction with their care and health service use.

DATA COLLECTION AND ANALYSIS

Assessments of trial eligibility, quality and data extractions were done by at least two of the reviewers.

MAIN RESULTS

Over 2000 women were recruited into the 23 included trials. Only nine trials were rated of high quality for the concealment of allocation. In the magnesium sulphate versus control (all studies) no difference was seen for the risk of birth within 48 hours of treatment for women given magnesium sulphate compared with controls when using a random effects model (relative risk (RR) 0.85, 95% confidence interval (CI) 0.58-1.25, 11 trials, 881 women). No benefit was seen for magnesium sulphate on the risk of giving birth preterm (<37 weeks) or very preterm (<34 weeks). The risk of death (fetal and paediatric) was higher for infants exposed to magnesium sulphate (RR 2.82, 95% CI 1.20-6.62, 7 trials, 727 infants). There were only two fetal deaths, both in the magnesium sulphate group in one study. The six other trials reported there were no fetal deaths. No differences for total paediatric mortality were shown in the six trials with data. No beneficial effect was seen from using magnesium sulphate on the risk of other neonatal morbidity. A non-significant reduction in the risk of cerebral palsy was reported at follow up at 18 months corrected age (RR 0.14, 95% CI 0.01-2.60, 1 trial, 99 children).

REVIEWER'S CONCLUSIONS

Magnesium sulphate is ineffective at delaying birth or preventing preterm birth, and its use is associated with an increased mortality for the infant. Any further trials should be of high quality, large enough to assess serious morbidity and mortality, compare different dose regimens, and provide neurodevelopmental status of the child.

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.

New developments in the management of preterm labor

Current management of preterm labor has not changed the incidence of preterm delivery; therefore, significant research effort has been concentrated on the search for new methods of management. New tocolytics like inhibitors of cyclooxygenase 2 and nitric oxide donors have been tested in animal models and in preliminary clinical trials with promising results. Inhibition of cervical ripening may be one alternative to tocolysis. This new approach has a potential to be a valuable method of management of preterm labor if human studies confirm the promising results reported in animals. Growing evidence suggests that premature delivery may be associated with infection or fetal growth abnormalities, with dire consequences to the fetus. If these associations are to be included in risk and benefit assessment, then inhibition of preterm labor may prove to be detrimental to the fetus.