Betamimetics for inhibiting preterm labour

Efficacy of Transdermal Nitroglycerin Patch for the Arrest of Preterm Labor: A Retrospective Study

Background Transdermal nitroglycerin (NTG) is a potent smooth muscle relaxant acting as a tocolytic agent by acting on the uterine muscles. The transdermal patch allows for continuous and controlled release of NTG through the skin into the bloodstream. This method offers the advantage of sustained drug delivery over a prolonged period. Objective of the study The study aimed to evaluate the efficacy of NTG patches for the arrest of preterm labor. Materials and methods This retrospective study comprised 100 patients admitted to our tertiary care center, ranging from 27 to 35 weeks of gestation, exhibiting preterm labor, uterine contractions, effacement, and dilatation of the cervix, without comorbidities and complications. Results In this study, it was observed that the incidence of preterm labor was higher among women aged 21-25 years. Pregnancy duration was extended by an average of approximately 28.63 days in our study cohort, with 90% of patients experiencing a prolongation of pregnancy to 48 hours after the application of a transdermal NTG patch. Parity distribution showed 50% of patients having a parity of G2-G4 and 30% being primigravida. However, 40% of the participants reported experiencing side effects, including headaches (15%) and local reactions (25%), while 60% did not experience any adverse effects. Conclusion In this study we found that the application of transdermal NTG patches led to a mean prolongation of pregnancy by 28.63 days, allowing time for the administration of steroids and fetal maturation. The inhibition of preterm contractions was successful, with an efficacy rate of 92%. These findings suggest the potential effectiveness of transdermal NTG patches as a tocolytic agent in managing preterm labor. However, the occurrence of side effects highlights the importance of careful monitoring and management during treatment.

The combined uterorelaxant effect of sildenafil and terbutalin in the rat: The potential benefit of co-administration of low doses

Aims

Our aims were to investigate the uterus relaxant effect of sildenafil alone and co-administered with β2-mimetic terbutaline in an isolated organ bath and to perform in vivo smooth muscle electromyographic studies in pregnant rats. The modifications in uterine cAMP/cGMP levels were also detected.

Main methods

Contractions of non-pregnant and 5/15/18/20/22-day pregnant uterine rings were measured in an isolated organ bath system in the presence of sildenafil alone or with terbutaline. The uterine levels of cAMP and cGMP were determined by commercial ELISA assays. The in vivo efficacy of the combination was measured by smooth muscle electromyography.

Key findings

Sildenafil reduced uterine contractions in vitro and in vivo; additionally, terbutaline significantly increased the uterorelaxant effect of sildenafil in the lower concentration or dose ranges. Terbutaline enhanced the cGMP level increasing effect of sildenafil.

Significance

The co-administration of sildenafil and terbutaline could be a promising tocolytic combination to reduce maternal and foetal adverse events and increase efficacy.

Fetal echocardiographic evaluation before and after nifedipine treatment in preterm labor

OBJECTIVE

To assess the effect of nifedipine used for tocolysis on cardiac morphology and functions.

METHODS

The study included 47 pregnant women diagnosed with preterm labor at 32-33 weeks. Fetal echocardiographic evaluation was performed with two-dimensional (2D) imaging, M-mode, pulsed wave (PW) Doppler, and tissue Doppler imaging (TDI) before and after the 48^th hour of nifedipine treatment.

RESULTS

No significant change was observed in Doppler parameters (pulsatility indices of the umbilical artery, middle cerebral artery, ductus venosus) and cardiac morphology (cardiothoracic ratio, end-diastolic longitudinal diameters, sphericity indices, wall thickness) after nifedipine treatment. The parameters obtained with TDI (e', a', s', e'/a', E/e' of mitral and tricuspid valves), M- mode (TAPSE, MAPSE), pulsed Doppler (myocardial performance index, left cardiac output, right cardiac output, tricuspid E, A waves, tricuspid E/A ratio, mitral E, A waves, mitral E/A ratio) did not change after nifedipine treatment.

CONCLUSION

To date, this is the first study to examine the effects of nifedipine on the fetal heart using the TDI. Since nifedipine is a drug that is frequently used and well-tolerated in the prevention of preterm labor, it is crucial that it does not cause changes in fetal cardiac parameters during tocolysis. Therefore, we used TDI in addition to conventional methods to evaluate the effect of nifedipine, which is frequently used in obstetrics, on cardiac functions in the early period. Nifedipine treatment seems not to affect systolic or diastolic functions. This indicates that nifedipine is reliable on cardiac functions and morphology in pregnancies treated for preterm labor.

Chinese Herbal Medicines Have Potentially Beneficial Effects on the Perinatal Outcomes of Pregnant Women

Introduction: Tocolytic treatment is beneficial to pregnant women with a risk of premature labor or miscarriage. However, previous reports have shown that progestogen might not be effective and ritodrine may increase the risk of maternal vascular-related diseases. Chinese herbal products (CHP) are used as alternative therapies for pregnant women. The goal was to evaluate the efficacy of combined tocolytic therapy and CHP therapy in pregnancy outcomes for pregnant women in Taiwan.

Materials and Methods: We conducted a retrospective cohort study based on the National Health Insurance Research Database. A total of 47,153 pregnant women treated with tocolytics aged 18–50 years from 2001 to 2015 were selected from two million random samples. According to the medical use of tocolytics and CHP, we divided the users into two groups: western medicine (WM) only (n = 40,961) and WM/CHP (n = 6,192) groups. A propensity score (PS)-matched cohort (6,192 pairs) was established based on baseline confounders. All participants were followed up to perinatal outcomes. Conditional logistic regression analysis was used to examine the effects of CHP use on the odds of miscarriage and preterm birth.

Results: The adjusted odds ratio (OR) for premature birth in the WM/CHP group (n = 411, 6.64%) was significantly lower than in the WM group (n = 471, 7,61%) (0,86, 95% confidence interval [CI], 0.74–0.99). Further subgroup analysis based on the usage of formulae that activate blood and remove stasis or purgative formulae, the adjusted OR of preterm birth of those using these formulae was significantly lower in the WM/CHP group (n = 215, 6.32%) than that in the WM group (n = 265, 7.77%) (OR: 0.79, 95% CI: 0.65–0.96).

Conclusion: We found that the combination of CHP and tocolytics can be beneficial to pregnant women in the prevention of premature birth. Further research is required to investigate causal relationships.

Myometrial-derived CXCL12 promotes lipopolysaccharide induced preterm labour by regulating macrophage migration, polarization and function in mice

Preterm birth is a major contributor to neonatal mortality and morbidity. Infection results in elevation of inflammation-related cytokines followed by infiltration of immune cells into gestational tissue. CXCL12 levels are elevated in preterm birth indicating it may have a role in preterm labour (PTL); however, the pathophysiological correlations between CXCL12/CXCR4 signalling and premature labour are poorly understood. In this study, PTL was induced using lipopolysaccharide (LPS) in a murine model. LPS induced CXCL12 RNA and protein levels significantly and specifically in myometrium compared with controls (3-fold and 3.5-fold respectively). Highest levels were found just before the start of labour. LPS also enhanced the infiltration of neutrophils, macrophages and T cells, and induced macrophage M1 polarization. In vitro studies showed that condition medium from LPS-treated primary smooth muscle cells (SMC) induced macrophage migration, M1 polarization and upregulated inflammation-related cytokines such as interleukin (IL)-1, IL-6 and tumor necrosis factor alpha (TNF-α). AMD3100 treatment in pregnant mice led to a significant decrease in the rate of PTL (70%), prolonged pregnancy duration and suppressed macrophage infiltration into gestation tissue by 2.5-fold. Further, in-vitro treatment of SMC by AMD3100 suppressed the macrophage migration, decreased polarization and downregulated IL-1, IL-6 and TNF-α expression. LPS treatment in pregnant mice induced PTL by increasing myometrial CXCL12, which recruits immune cells that in turn produce inflammation-related cytokines. These effects stimulated by LPS were completely reversed by AMD3100 through blocking of CXCL12/CXCR4 signalling. Thus, the CXCL12/CXCR4 axis presents an excellent target for preventing infection and inflammation-related PTL.

Guideline No. 401: Sonographic Cervical Length in Singleton Pregnancies: Techniques and Clinical Applications

OBJECTIVES

• To assess the association between sonography-derived cervical length measurement and preterm birth. • To describe the various techniques to measure cervical length using sonography. • To review the natural history of the short cervix. • To review the clinical uses, predictive ability, and utility of sonography-measured short cervix.

OUTCOMES

Reduction in rates of prematurity and/or better identification of those at risk, as well as possible prevention of unnecessary interventions.

INTENDED USERS

Clinicians involved in the obstetrical management or cervical imaging of patients at increased risk of a short cervix.

TARGET POPULATION

Women at increased risk of a short cervix or at risk of preterm birth.

EVIDENCE

Literature published up to June 2019 was retrieved through searches of PubMed and the Cochrane Library using appropriate controlled vocabulary and key words (preterm labour, ultrasound, cervix, cervical insufficiency, transvaginal, transperineal, cervical length, fibronectin). Results were restricted to general and systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. There were no date or language restrictions. Grey (unpublished) literature was identified through searching the websites of health technology assessment agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUES

The evidence and this guideline were reviewed by the Diagnostic Imaging Committee of the Society of Obstetricians and Gynaecologists of Canada, and the recommendations were made and graded according to the rankings of the Canadian Task Force on Preventive Health Care (Online Appendix Table A1).

BENEFITS, HARMS, COSTS

Preterm birth is a leading cause of perinatal morbidity and mortality. Use of the sonographic technique reviewed in this guideline may help identify women at risk of preterm birth and, in some circumstances, lead to interventions that may reduce the rate of preterm birth. SUMMARY STATEMENTS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES): RECOMMENDATIONS (CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE GRADING IN PARENTHESES).

The determinant role of IL-6 in the establishment of inflammation leading to spontaneous preterm birth

Preterm birth (PTB) and its consequences are a major public health concern as preterm delivery is the main cause of mortality and morbidity at birth. There are many causes of PTB, but inflammation is undeniably associated with the process of premature childbirth and fetal injury. At present, treatments clinically available mostly involve attempt to arrest contractions (tocolytics) but do not directly address upstream maternal inflammation on development of the fetus. One of the possible solutions may lie in the modulation of inflammatory mediators. Of the many pro-inflammatory cytokines involved in the induction of PTB, IL-6 stands out for its pleiotropic effects and its involvement in both acute and chronic inflammation. Here, we provide a detailed review of the effects of IL-6 on the timing of childbirth, its occurrence during PTB and its indissociable roles with associated fetal tissue damage.

In utero exposure to ritodrine during pregnancy and risk of autism in their offspring until 8 years of age

Beta-2 adrenergic receptor (B2AR) agonists, used as asthma treatments and tocolytics during pregnancy, have recently been reported to be associated with autism in their offspring. However, the particular link between autism and ritodrine, a common type of B2AR agonist used solely as tocolytics, has never been substantiated with any nationwide database. Thus, we aimed to examine the association between in utero exposure of ritodrine and the risk of autism in their offspring using a national database. This population-based cohort study was conducted by merging the Korea National Health Insurance claims database and National Health Screening Program for Infants and Children database. These databases included all women who had delivered singleton between January 2007 and December 2008 in Korea. Out of the total 770,016 mothers, 30,959 (4.02%) were exposed to ritodrine during pregnancy, and 5583 (0.73%) of their children were identified as having autism, defined until 8 years of age. According to our analysis, the overall cumulative incidence of autism up to 8 years was 1.37% in ritodrine exposure group and 0.70% in ritodrine non-exposure group (p < 0.05, log-rank test). By Cox proportional hazard analysis, use of ritodrine in preterm birth was associated with significantly higher hazard of autism [adjusted hazard ratio: 1.23, 95% CI 1.04-1.47], after adjusting for confounding variables including maternal age, parity, cesarean section, preterm labor, steroid use, birth weight, gender, and preeclampsia. Thus, in utero exposure to ritodrine was associated with an increased risk of autism in their offspring.

Effect of dual tocolysis with fenoterol and atosiban in human myometrium

Objectives To measure the tocolytic effect of the combination of the oxytocin receptor antagonist atosiban with the β-mimetic agent fenoterol on human myometrium of pregnant women. Methods An in vitro study of contractility in human myometrium at the Laboratory of the Department of Obstetrics, University Hospital of Zürich, Switzerland, was performed. Thirty-six human myometrial biopsies were obtained during elective caesarean sections of singleton pregnancies at term. Tissue samples were exposed to atosiban, fenoterol and the combination of atosiban with fenoterol. Contractility was measured as area under the curve during 30 min of spontaneous contractions. The effect of treatment was expressed as the percentage of change from basal activity during 30 min of exposure. Differences were calculated using a paired Wilcoxon signed-rank test. An additive effect of dual tocolysis was assumed when no significant difference was detected between the observed and expected inhibition of dual tocolysis. When inhibition was greater or lower than expected, the dual combination was characterised as "synergistic" or "antagonistic", respectively. Results Atosiban and fenoterol alone suppressed contractions by a median of 43.2% and 29.8%, respectively. The combination of atosiban plus fenoterol was measured at a level of 67.3% inhibition. There was no significant difference in the expected (63.2%) and observed inhibition effect of dual tocolysis (P=0.945). Conclusion This study demonstrated an additive effect of dual tocolysis of atosiban and fenoterol on human myometrium in vitro, but no synergistic or antagonistic effect.

Acute Tocolysis - a Critical Analysis of Evidence-Based Data

Tocolysis is among the most common obstetric measures. The objective is to prolong the pregnancy by at least 48 hours to complete foetal lung maturation and for the in-utero transfer of the pregnant woman to a perinatal centre. The indication for tocolysis is regular, premature contractions (≥ 4/20 min) and a dynamic shortening of the cervical length/cervical opening between 22 + 0 to 33 + 6 weeks of pregnancy. In this connection, the cervical length measured on ultrasound and the determination of biomarkers in the cervicovaginal secretions can be important decision-making aids. Beta sympathomimetics should no longer be used due to the high rate of severe maternal adverse effects. Given controversial data, magnesium sulphate is no longer recommended for tocolysis in current guidelines. Atosiban is as effective for prolonging pregnancy as beta sympathomimetics and nifedipine, has the lowest rate of maternal adverse effects, but also the highest drug costs. Nifedipine and indomethacin are recommended in international guidelines for acute tocolysis, however there are indications of increased neonatal morbidity following indomethacin. Current problems are, above all, the lack of randomised, controlled comparative and placebo-controlled studies, the data which are controversial to some extent, and the insufficient evidence of tocolytics to significantly improve the neonatal outcome.

Medical and Surgical Interventions Available Before a Periviable Birth

Periviable birth contributes disproportionately to perinatal morbidity and mortality. By analyzing the most relevant outcomes after a preterm birth some information can be provided on the potential benefit of interventions. This article discusses surgical and medical interventions that may offer neonatal benefit including cerclage, amniocentesis, progesterone, antenatal corticosteroids, magnesium sulfate for neuroprotection, and tocolysis. Cervical cerclage has the greatest promise at reducing morbidity and mortality related to periviable birth even though it may not reduce the overall preterm birth rate. The use of antenatal corticosteroids, magnesium sulfate, progesterone, and tocolytics may also improve outcome. Studies specifically evaluating these interventions are needed.

Towards evidence-based resuscitation of the newborn infant

Effective resuscitation of the newborn infant has the potential to save many lives around the world and reduce disabilities in children who survive peripartum asphyxia. In this Series paper, we highlight some of the important advances in the understanding of how best to resuscitate newborn infants, which includes monitoring techniques to guide resuscitative efforts, increasing awareness of the adverse effects of hyperoxia, delayed umbilical cord clamping, the avoidance of routine endotracheal intubation for extremely preterm infants, and therapeutic hypothermia for hypoxic-ischaemic encephalopathy. Despite the challenges of performing high-quality clinical research in the delivery room, researchers continue to refine and advance our knowledge of effective resuscitation of newborn infants through scientific experiments and clinical trials.

Home uterine monitoring for detecting preterm labour

BACKGROUND

To reduce the morbidity and mortality associated with preterm birth, home uterine activity monitoring aims for early detection of increased contraction frequency, and early intervention with tocolytic drugs to inhibit labour and prolong pregnancy. However, the effectiveness of such monitoring is disputed.

OBJECTIVES

To determine whether home uterine activity monitoring is effective in improving the outcomes for women and their infants considered to be at high risk of preterm birth, when compared with conventional or other care packages that do not include home uterine monitoring.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 October 2014), CENTRAL (The Cochrane Library 2014, Issue 8), MEDLINE (1966 to 31 August 2014), EMBASE (1974 to 31 August 2014), CINAHL (1982 to 31 August 2014) and scanned reference lists of retrieved studies.

SELECTION CRITERIA

Randomised control trials of home uterine activity monitoring, with or without patient education programmes, for women at risk for preterm birth, in comparison to the same care package without home uterine activity monitoring.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We did not attempt to contact authors to resolve queries.

MAIN RESULTS

There were 15 included studies (total number of enrolled participants 6008); 13 studies contributed data. Women using home uterine monitoring were less likely to experience preterm birth at less than 34 weeks (risk ratio (RR) 0.78; 95% confidence interval (CI) 0.62 to 0.99; three studies, n = 1596; fixed-effect analysis) (GRADE high). The significant difference was not evident when we carried out a sensitivity analysis, restricting the analysis to studies at low risk of bias based on study quality (RR 0.75; 95% CI 0.57 to 1.00, one study, 1292 women). There was no significant difference in the rate of perinatal mortality (RR 1.22; 95% CI 0.86 to 1.72; two studies, n = 2589) (GRADE low)There was no significant difference in the number of preterm births at less than 37 weeks (average RR 0.85; CI 0.72 to 1.01; eight studies, n = 4834; random-effects, T² = 0.03, I² = 68%) (GRADE very low). Infants born to women using home uterine monitoring were less likely to be admitted to neonatal intensive care unit (average RR 0.77; 95% CI 0.62 to 0.96; five studies, n = 2367; random-effects, T² = 0.02, I² = 32%) (GRADE moderate). The difference was not statistically significant when only high quality studies were included (RR 0.86; 95% CI 0.74 to 1.01; one study, n = 1292). Women using home uterine monitoring made more unscheduled antenatal visits (mean difference (MD) 0.49; 95% CI 0.39 to 0.62; two studies, n = 3707) (GRADE moderate). Women using home uterine monitoring were also more likely to have prophylactic tocolytic drug therapy (average RR 1.21; 95% CI 1.01 to 1.45; seven studies, n = 4316; random-effects. T² = 0.03, I² = 62%) but this difference was no longer significant when the analysis was restricted to higher quality studies (average RR 1.22; 95% CI 0.90 to 1.65, three studies, n = 3749,random-effects, T² = 0.05, I² = 76%) (GRADE low). One small study reported that the home uterine monitoring group spent fewer days in hospital antenatally. No data on maternal anxiety or acceptability were found.

AUTHORS' CONCLUSIONS

Home uterine monitoring may result in fewer admissions to a neonatal intensive care unit but more unscheduled antenatal visits and tocolytic treatment, but the level of evidence is generally low to moderate. Important group differences were not evident when sensitivity analysis was undertaken using only high quality trials. There is no impact on maternal and perinatal outcomes such as perinatal mortality or incidence of preterm birth.

Use of antenatal corticosteroids and tocolytic drugs in preterm births in 29 countries: an analysis of the WHO Multicountry Survey on Maternal and Newborn Health

BACKGROUND

Despite the global burden of morbidity and mortality associated with preterm birth, little evidence is available for use of antenatal corticosteroids and tocolytic drugs in preterm births in low-income and middle-income countries. We analysed data from the WHO Multicountry Survey on Maternal and Newborn Health (WHOMCS) to assess coverage for these interventions in preterm deliveries.

METHODS

WHOMCS is a facility-based, cross-sectional survey database of birth outcomes in 359 facilities in 29 countries, with data collected prospectively from May 1, 2010, to Dec 31, 2011. For this analysis, we included deliveries after 22 weeks' gestation and we excluded births that occurred outside a facility or quicker than 3 h after arrival. We calculated use of antenatal corticosteroids in women who gave birth between 26 and 34 weeks' gestation, when antenatal corticosteroids are known to be most beneficial. We also calculated use in women at 22-25 weeks' and 34-36 weeks' gestation. We assessed tocolytic drug use, with and without antenatal corticosteroids, in spontaneous, uncomplicated preterm deliveries at 26-34 weeks' gestation.

FINDINGS

Of 303,842 recorded deliveries after 22 weeks' gestation, 17,705 (6%) were preterm. 3900 (52%) of 7547 women who gave birth at 26-34 weeks' gestation, 94 (19%) of 497 women who gave birth at 22-25 weeks' gestation, and 2276 (24%) of 9661 women who gave birth at 35-36 weeks' gestation received antenatal corticosteroids. Rates of antenatal corticosteroid use varied between countries (median 54%, range 16-91%; IQR 30-68%). Of 4677 women who were potentially eligible for tocolysis drugs, 1276 (27%) were treated with bed rest or hydration and 2248 (48%) received no treatment. β-agonists alone (n=346, 7%) were the most frequently used tocolytic drug. Only 848 (18%) of potentially eligible women received both a tocolytic drug and antenatal corticosteroids.

INTERPRETATION

Use of interventions was generally poor, despite evidence for their benefit for newborn babies. A substantial proportion of antenatal corticosteroid use occurred at gestational ages at which benefit is controversial, and use of less effective or potentially harmful tocolytic drugs was common. Implementation research and contextualised health policies are needed to improve drug availability and increase compliance with best obstetric practice.

FUNDING

UNDP-UNFPA-UNICEF-WHO-World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP); WHO; USAID; Ministry of Health, Labour and Welfare of Japan; Gynuity Health Projects.

Synthesis of azabicycloalkanone amino acid and azapeptide mimics and their application as modulators of the prostaglandin F2α receptor for delaying preterm birth

Premature birth (<37 weeks gestation) is the major cause of perinatal mortality and morbidity and has been steadily increasing worldwide. Towards the rational design of more effective therapeutic agents for inhibiting uterine contractions and prolonging gestation (a so-called tocolytic drug), our team has targeted the prostaglandin F2α receptor (FP) employing a peptidomimetic approach designed to provide modulators of this novel target. We identified first a lead peptide (PDC113) (1) based on the sequence of the second extracellular loop of FP on the basis that the loop itself might modulate receptor activation. Systematic study of the structure−activity relationships of 1 generated hypotheses concerning the conformation and side-chains responsible for activity that led to the synthesis of PDC113.31 (2), a potent all d-amino acid peptide, which has successfully completed Phase 1b clinical trials. Employing indolizidinone amino acids, peptide mimics were developed that served to probe the mechanism of FP modulation. For example, PDC113.824 (9) was shown to allosterically regulate FP activity contingent on the presence of prostaglandin F2α by a mechanism implicating biased signalling. Although attempts to understand the turn geometry responsible for the activity of 9 by replacement of its indolizidin-2-one moiety with other azabicycloalkanones failed to produce biologically active analogs, employment of aza-aminoacyl-proline analogs resulted in a series of FP modulators exhibiting distinct effects on different G protein-mediated signalling pathways. Our program has thus contributed novel probes for understanding the chemical biology of FP as well as new therapeutic agents with promise for inhibiting uterine contractions and preventing preterm birth.

Intrapartum obstetric management

Maternal cardiac disease complicates approximately 1-2% of all pregnancies in the United States. Just as during the antepartum period, in the immediate period surrounding delivery, obstetrical patients with cardiac disease (both congenital and acquired) will have specialized needs, tailored to the patient and her specific lesion. While the basic principles of labor and delivery management protocols are relevant to this subgroup of patients, there are certain areas in which adjustments must be made. These include endocarditis prophylaxis, recent anticoagulation, fluid management, and the need for increased maternal cardiac monitoring. Awareness of the challenges of the intrapartum period combined with a multi-disciplinary approach from anesthesia, cardiology, and the obstetrical provider will optimize the patient for a safe delivery.

Combination of tocolytic agents for inhibiting preterm labour

BACKGROUND

Preterm birth represents the single largest cause of mortality and morbidity for newborns and a major cause of morbidity for pregnant women. Tocolytic agents include a wide range of drugs that can inhibit labour to prolong pregnancy. This may gain time to allow the fetus to mature further before being born, permit antenatal corticosteroid administration for lung maturation, and allow time for intra-uterine transfer to a hospital with neonatal intensive care facilities. However, some tocolytic drugs are associated with severe side effects. Combinations of tocolytic drugs may be more effective over single tocolytic agents or no intervention, without adversely affecting the mother or neonate.

OBJECTIVES

To assess the effects on maternal, fetal and neonatal outcomes of any combination of tocolytic drugs for the treatment of preterm labour when compared with any other treatment, no treatment or placebo.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2014) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials comparing a combination of tocolytic agents, administered by any route or any dose, for inhibiting preterm labour versus any other treatment (including other combinations of tocolytics or single tocolytics), no intervention or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study reports for eligibility, carried out data extraction and assessed risk of bias.

MAIN RESULTS

Eleven studies met our inclusion criteria. Two studies did not report any outcome data relevant to the review, so the results of the review are based on nine trials that contributed data. Primary outcomes were perinatal mortality, serious maternal or infant outcomes, adverse drug reactions, birth before 48 hours of trial entry, birth before 34 weeks' gestation and preterm neonates delivered without a full course of antenatal steroids completed 24 hours before birth. The quality of evidence in included trials was mixed; only three of the trials were placebo controlled.The included trials examined seven different comparisons: intravenous (IV) ritodrine plus oral or IV magnesium (sulphate or gluconate) versus IV ritodrine alone (three trials, 231 women); IV ritodrine plus indomethacin suppositories versus IV ritodrine alone (one trial, 208 women); IV ritodrine plus vaginal progesterone versus IV ritodrine alone (one trial, 83 women); IV hexoprenaline sulphate plus IV magnesium hydrochloride versus IV hexoprenaline sulphate alone (one trial, 24 women); IV fenoterol plus oral naproxen versus IV fenoterol alone (one trial, 72 women); oral pentoxifylline plus IV magnesium sulphate plus IV fenoterol versus IV magnesium sulphate plus IV fenoterol (one trial, 125 women); and, IV terbutaline plus oral metoprolol versus IV terbutaline alone (one trial, 17 women). Few studies with small numbers of women were available for each comparison, hence very little data were pooled in meta-analysis. In all trials, not many of the primary outcomes were reported.Three trials examined intravenous (IV) ritodrine plus IV or oral magnesium (sulphate or gluconate) compared with IV ritodrine alone. One study, with 41 women, reported more adverse drug reactions in the group receiving the combined tocolytics (risk ratio (RR) 7.79, 95% confidence interval (CI) 1.11 to 54.80). Two trials reported discontinuation of therapy due to severe side effects (results were not combined due to high statistical heterogeneity, I² = 83%); one trial reported increased severe side effects in the group receiving IV ritodrine alone (RR 7.79, 95% CI 1.11 to 54.80, 41 women); in the other trial there was no clear difference between groups (RR 0.23, 95% CI 0.03 to 1.97, 107 women). Other primary outcomes were not reported.One trial assessed IV ritodrine plus indomethacin suppositories versus IV ritodrine alone. There were no significant differences between groups for perinatal mortality or serious neonatal morbidity. Results for other primary outcomes were not reported.There were no significant differences between groups receiving IV ritodrine plus vaginal progesterone compared with IV ritodrine alone for most outcomes reported, although the latency period (time from recruitment to delivery) was increased in the group receiving the combination of tocolytics.For other combinations of tocolytic agents, primary outcomes were rarely reported and for secondary outcomes results did not demonstrate differences between groups.

AUTHORS' CONCLUSIONS

It is unclear whether a combination of tocolytic drugs for preterm labour is more advantageous for women and/or newborns due to a lack of large, well-designed trials including the outcomes of interest. There are no trials of combination regimens using widely used tocolytic agents, such as calcium channel blockers (nifedipine) and/or oxytocin receptor antagonists (atosiban). Further trials are needed before specific conclusions on use of combination tocolytic therapy for preterm labour can be made.

Oxytocin receptor antagonists for inhibiting preterm labour

BACKGROUND

Preterm birth, defined as birth between 20 and 36 completed weeks, is a major contributor to perinatal morbidity and mortality globally. Oxytocin receptor antagonists (ORA), such as atosiban, have been specially developed for the treatment of preterm labour. ORA have been proposed as effective tocolytic agents for women in preterm labour to prolong pregnancy with fewer side effects than other tocolytic agents.

OBJECTIVES

To assess the effects on maternal, fetal and neonatal outcomes of tocolysis with ORA for women with preterm labour compared with placebo or any other tocolytic agent.

SEARCH METHODS

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

SELECTION CRITERIA

We included all randomised controlled trials (published and unpublished) of ORA for tocolysis of labour between 20 and 36 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated methodological quality and extracted trial data. When required, we sought additional data from trial authors. Results are presented as risk ratio (RR) for categorical and mean difference (MD) for continuous data with the 95% confidence intervals (CI). Where appropriate, the number needed to treat for benefit (NNTB) and the number needed to treat for harm (NNTH) were calculated.

MAIN RESULTS

This review update includes eight additional studies (790 women), giving a total of 14 studies involving 2485 women.Four studies (854 women) compared ORA (three used atosiban and one barusiban) with placebo. Three studies were considered at low risk of bias in general (blinded allocation to treatment and intervention), the fourth study did not adequately blind the intervention. No difference was shown in birth less than 48 hours after trial entry (average RR 1.05, 95% CI 0.15 to 7.43; random-effects, (two studies, 152 women), perinatal mortality (RR 2.25, 95% CI 0.79 to 6.38; two studies, 729 infants), or major neonatal morbidity. ORA (atosiban) resulted in a small reduction in birthweight (MD -138.86 g, 95% CI -250.53 to -27.18; two studies with 676 infants). In one study, atosiban resulted in an increase in extremely preterm birth (before 28 weeks' gestation) (RR 3.11, 95% CI 1.02 to 9.51; NNTH 31, 95% CI 8 to 3188) and infant deaths (up to 12 months) (RR 6.13, 95% CI 1.38 to 27.13; NNTH 28, 95% CI 6 to 377). However, this finding may be confounded due to randomisation of more women with pregnancy less than 26 weeks' gestation to atosiban. ORA also resulted in an increase in maternal adverse drug reactions requiring cessation of treatment in comparison with placebo (RR 4.02, 95% CI 2.05 to 7.85; NNTH 12, 95% CI 5 to 33). No differences were shown in preterm birth less than 37 weeks' gestation or any other adverse neonatal outcomes. No differences were evident by type of ORA, although data were limited.Eight studies (1402 women) compared ORA (atosiban only) with betamimetics; four were considered of low risk of bias (blinded allocation to treatment and to intervention). No statistically significant difference was shown in birth less than 48 hours after trial entry (RR 0.89, 95% CI 0.66 to 1.22; eight studies with 1389 women), very preterm birth (RR 1.70, 95% CI 0.89 to 3.23; one study with 145 women), extremely preterm birth (RR 0.84, 95% CI 0.37 to 1.92; one study with 244 women) or perinatal mortality (RR 0.55, 95% CI 0.21 to 1.48; three studies with 816 infants). One study (80 women), of unclear methodological quality, showed an increase in the interval between trial entry and birth (MD 22.90 days, 95% CI 18.03 to 27.77). No difference was shown in any reported measures of major neonatal morbidity (although numbers were small). ORA (atosiban) resulted in less maternal adverse effects requiring cessation of treatment (RR 0.05, 95% CI 0.02 to 0.11; NNTB 6, 95% CI 6 to 6; five studies with 1161 women).Two studies including (225 women) compared ORA (atosiban) with calcium channel blockers (CCB) (nifedipine only). The studies were considered as having high risk of bias as neither study blinded the intervention and in one study it was not known if allocation was blinded. No difference was shown in birth less than 48 hours after trial entry (average RR 1.09, 95% CI 0.44 to 2.73, random-effects; two studies, 225 women) and extremely preterm birth (RR 2.14, 95% CI 0.20 to 23.11; one study, 145 women). No data were available for the outcome of perinatal mortality. One small trial (145 women), which did not employ blinding of the intervention, showed an increase in the number of preterm births (before 37 weeks' gestation) (RR 1.56, 95% CI 1.13 to 2.14; NNTH 5, 95% CI 3 to 19), a lower gestational age at birth (MD -1.20 weeks, 95% CI -2.15 to -0.25) and an increase in admission to neonatal intensive care unit (RR 1.70, 95% CI 1.17 to 2.47; NNTH 5, 95% CI 3 to 20). ORA (atosiban) resulted in less maternal adverse effects (RR 0.38, 95% CI 0.21 to 0.68; NNTB 6, 95% CI 5 to 12; two studies, 225 women) but not maternal adverse effects requiring cessation of treatment (RR 0.36, 95% CI 0.01 to 8.62; one study, 145 women). No longer-term outcome data were included.

AUTHORS' CONCLUSIONS

This review did not demonstrate superiority of ORA (largely atosiban) as a tocolytic agent compared with placebo, betamimetics or CCB (largely nifedipine) in terms of pregnancy prolongation or neonatal outcomes, although ORA was associated with less maternal adverse effects than treatment with the CCB or betamimetics. The finding of an increase in infant deaths and more births before completion of 28 weeks of gestation in one placebo-controlled study warrants caution. However, the number of women enrolled at very low gestations was small. Due to limitations of small numbers studied and methodological quality, further well-designed randomised controlled trials are needed. Further comparisons of ORA versus CCB (which has a better side-effect profile than betamimetics) are needed. Consideration of further placebo-controlled studies seems warranted. Future studies of tocolytic agents should measure all important short- and long-term outcomes for women and infants, and costs.

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.

Short-term tocolytics for preterm delivery - current perspectives

Administration of short-term tocolytic agents can prolong pregnancy for women in preterm labor. Prolonging pregnancy has many benefits because it allows for other proven interventions, such as antenatal corticosteroid administration, to be accomplished. This review provides an overview of currently utilized tocolytic agents and the evidence demonstrating their efficacy for prolonging pregnancy by at least 48 hours. General pharmacological principles for the clinician regarding drugs in pregnancy are also briefly discussed. In general, while the choice of the best first-line short-term tocolytic drug is not clear, it is evident that use of these agents has a clear place in current obstetric therapeutics.

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.

Betamimetics for inhibiting preterm labour

BACKGROUND

Preterm birth is a major contributor to perinatal mortality and morbidity worldwide. Tocolytic agents are drugs used to inhibit uterine contractions. Betamimetics are tocolytic agents that have been widely used, especially in resource-poor countries.

OBJECTIVES

To assess the effects of betamimetics given to women with preterm labour.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 December 2013) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials of betamimetics, administered by any route or any dose, in the treatment of women in preterm labour where betamimetics were compared with other betamimetics, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two review authors assessed risk of bias and extracted the data independently.

MAIN RESULTS

Twenty-eight trials were assessed as eligible for inclusion in the review, but eight did not report any outcome data relevant to the review. Results are based on the 20 trials that contributed data.Twelve trials, involving 1367 women, compared betamimetics with placebo. Betamimetics decreased the number of women in preterm labour giving birth within 48 hours (average risk ratio (RR) 0.68, 95% confidence interval (CI) 0.53 to 0.88, 10 trials, 1209 women). There was a decrease in the number of births within seven days (average RR 0.80; 95% CI 0.65 to 0.98, five trials, 911 women) but there was no evidence of a reduction in preterm birth (before 37 weeks' gestation) (RR 0.95; 95% CI 0.88 to 1.03, 10 trials, 1212 women). No benefit was demonstrated for betamimetics for perinatal death (RR 0.84; 95% CI 0.46 to 1.55, 11 trials, 1332 infants), or neonatal death (RR 0.90; 95% CI 0.27 to 3.00, six trials, 1174 infants). No significant effect was demonstrated for respiratory distress syndrome (RR 0.87; 95% CI 0.71 to 1.08, eight trials, 1239 infants). A few trials reported on cerebral palsy, infant death and necrotising enterocolitis; no significant differences between groups were identified for any of these outcomes. Betamimetics were significantly associated with the following outcomes: withdrawal from treatment due to adverse effects; maternal chest pain; dyspnoea; palpitation; tremor; headaches; hypokalaemia; hyperglycaemia; nausea or vomiting; nasal stuffiness; and fetal tachycardia.Nine trials compared different types of betamimetics. Other betamimetics were compared with ritodrine in five trials (n = 948). Other comparisons were examined in single trials: hexoprenaline compared with salbutamol (n = 140), slow versus moderate release salbutamol (n = 52) and salbutamol compared with terbutaline (n = 200). Trials were small, varied, and of insufficient quality to delineate any consistent patterns of effect.

AUTHORS' CONCLUSIONS

Betamimetics help to delay birth, which may give time to allow women to be transferred to tertiary care or to complete a course of antenatal corticosteroids. However, multiple adverse effects must be considered. The data are too few to support the use of any particular betamimetic.

Progestational agents for treating threatened or established preterm labour

BACKGROUND

Prematurity is not only the leading cause of perinatal morbidity and mortality but is associated with long-term impairment. Studies of various tocolytic agents have shown mixed results with little effect in improving pregnancy duration and insufficient data to confirm a definite beneficial effect on neonatal morbidity or mortality. Progesterone is known to have an inhibitory effect on uterine contractility and is thought to play a key role in the maintenance of pregnancy until term.

OBJECTIVES

To determine if the use of progestational agents is effective as a form of treatment or co-treatment for women with threatened or established preterm labour with intact membranes.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 August 2013), CENTRAL (The Cochrane Library 2013, Issue 10), MEDLINE (1966 to August 31 2013) and Embase (1974 to 31 August 2013). We checked the reference lists of all included studies to identify any additional studies and communicated with authors and the pharmaceutical industry.

SELECTION CRITERIA

Randomised controlled trials that compared progestational agents, given either alone or in combination with other tocolytics, with a control group receiving another tocolytic, placebo or no treatment, for the treatment of preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality.

MAIN RESULTS

Eight studies were included in this review, involving 563 women, but only seven studies, involving 538 women, contributed data for analyses. There are some data suggesting that the use of progestational agents results in a reduction of preterm deliveries at less than 37 weeks of gestation and an increase in birthweight. The use of a progestational agent may also reduce the frequency of uterine contractions, prolong pregnancy and attenuate the shortening of cervical length. However, the analysis was limited by the relatively small number of available studies. The power of the meta-analysis was also limited by the varying types, dosages and routes of administration of progesterone.

AUTHORS' CONCLUSIONS

There is insufficient evidence to advocate progestational agents as a tocolytic for women presenting with preterm labour.

A close look at the contraction and relaxation of the myometrium; the role of calcium

The function and regulation of the myometrium, especially during pregnancy, labour and birth are important in reproductive physiology. It is crucial to understand the mechanisms that generate and modulate uterine contractility in order to be able to prevent and/or treat the problems related with the myometrium. A limited understanding of the cellular and molecular events underlying these phenomena complicates the situation. Various agonists, hormones, transmitters and/or chemicals are related to the regulation of the functions of the myometrium. Although notable advances regarding the key steps in receptor signalling explaining the actions of these factors have been achieved, a good deal of information is still necessary to understand this vital process. A better comprehension of myometrium physiology and the translation of research findings to clinical settings will help progress in women's health. In this review, we attempt to present a critical overview of myometrial functions and focus specifically on the role of calcium.

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.

Prevention of periviable birth: bed rest, tocolysis, progesterone, and cerclage

The periviable period is associated with a rapid improvement in both mortality and morbidity with increasing gestational age. Therapies that can prolong gestation have the potential for markedly improving outcome compared to later in pregnancy. The therapies commonly prescribed in order to prolong gestation include bed rest, tocolysis, progesterone, and cerclage. Although these therapies are used to prevent preterm birth throughout gestation, their impact on perinatal outcome during the periviable period remains largely unknown. These therapies are discussed relative to the periviable period exploring available data and possible impact on perinatal outcome. Studies specifically evaluating therapeutic interventions during the periviable period are lacking.

Maintenance therapy with oxytocin antagonists for inhibiting preterm birth after threatened preterm labour

BACKGROUND

In some women, an episode of preterm labour settles and does not result in immediate preterm birth. Subsequent treatment with tocolytic agents such as oxytocin receptor antagonists may then have the potential to prevent the recurrence of preterm labour, prolonging gestation, and preventing the adverse consequences of prematurity for the infant.

OBJECTIVES

To assess the effects of maintenance therapy with oxytocin antagonists administered by any route after an episode of preterm labour in order to delay or prevent preterm birth.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 July 2013), sought ongoing and unpublished trials by contacting experts in the field and searched the reference lists of relevant articles.

SELECTION CRITERIA

Randomised controlled trials comparing oxytocin antagonists with any alternative tocolytic agent, placebo or no treatment, used for maintenance therapy after an episode of preterm labour.

DATA COLLECTION AND ANALYSIS

We used the standard methods of The Cochrane Collaboration and the Cochrane Pregnancy and Childbirth Group. Two review authors independently undertook evaluation of methodological quality and extracted trial data.

MAIN RESULTS

This review includes one trial of 513 women. When compared with placebo, atosiban did not reduce preterm birth before 37 weeks (risk ratio (RR) 0.89; 95% confidence intervals (CI) 0.71 to 1.12), 32 weeks (RR 0.85; 95% CI 0.47 to 1.55), or 28 weeks (RR 0.75; 95% CI 0.28 to 2.01). No difference was shown in neonatal morbidity, or perinatal mortality.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support the use of oxytocin receptor antagonists to inhibit preterm birth after a period of threatened or actual preterm labour. Any future trials using oxytocin antagonists or other drugs as maintenance therapy for preventing preterm birth should examine a variety of important infant outcome measures, including reduction of neonatal morbidity and mortality, and long-term infant follow-up. Future research should also focus on the pathophysiological pathways that precede preterm labour.

Magnesium maintenance therapy for preventing preterm birth after threatened preterm labour

BACKGROUND

Magnesium maintenance therapy is one of the types of tocolytic therapy used after an episode of threatened preterm labour (usually treated with an initial dose of tocolytic therapy) in an attempt to prevent the onset of further preterm contractions.

OBJECTIVES

To assess whether magnesium maintenance therapy is effective in preventing preterm birth after the initial threatened preterm labour is arrested.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2013).

SELECTION CRITERIA

Randomised controlled trials of magnesium therapy given to women after threatened preterm labour.

DATA COLLECTION AND ANALYSIS

The review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. We checked data entry.

MAIN RESULTS

We included four trials involving 422 women. Three trials had high risk of bias and none included any long-term follow-up of infants. No differences in the incidence of preterm birth or perinatal mortality were seen when magnesium maintenance therapy was compared with placebo or no treatment; or alternative therapies (ritodrine or terbutaline). The risk ratio (RR) for preterm birth (less than 37 weeks) for magnesium compared with placebo or no treatment was 1.05, 95% confidence interval (CI) 0.80 to 1.40 (two trials, 99 women); and 0.99, 95% CI 0.57 to 1.72 (two trials, 100 women) for magnesium compared with alternative therapies. The RR for perinatal mortality for magnesium compared with placebo or no treatment was 5.00, 95% CI 0.25 to 99.16 (one trial, 50 infants); and 5.00, 95% CI 0.25 to 99.16 (one trial, 50 infants) for magnesium compared with alternative treatments.Women taking magnesium preparations were less likely to report side effects (RR 0.67, 95% CI 0.47 to 0.96, three trials, 237 women), including palpitations or tachycardia (RR 0.26, 95% CI 0.13 to 0.52, three trials, 237 women) than women receiving alternative therapies. Women receiving magnesium were however, more likely to experience diarrhoea (RR 6.79, 95% CI 1.26 to 36.72, three trials, 237 women).

AUTHORS' CONCLUSIONS

There is not enough evidence to show any difference between magnesium maintenance therapy compared with either placebo or no treatment, or alternative therapies (ritodrine or terbutaline) in preventing preterm birth after an episode of threatened preterm labour.

The prevention, diagnosis and treatment of premature labor

BACKGROUND

The percentage of preterm births in Germany is high at 9%, but stable. 77% of cases of perinatal death are in prematurely born infants. Intensive research efforts are being directed toward the development of new means of primary and secondary prevention, diagnostic assessment, and pharmacotherapy of premature labor.

METHODS

We review pertinent publications that were retrieved by a selective search of the literature from 1966 to 2012, including current meta-analyses from the Cochrane database and the guidelines of German and foreign obstetric societies.

RESULTS

Preterm labor is a multifactorial problem. The current treatment options are symptomatic, rather than causally directed. Preventive treatment with progesterone can lower the rate of preterm birth in high-risk groups by more than 30%. Transporting the pregnant women to an appropriately qualified perinatal care center and induction of fetal lung maturation lowers perinatal mortality. A variety of tocolytic drugs with different mechanisms of action (betamimetics, oxytocin antagonists, calcium-channel blockers, NO donors, and inhibitors of prostaglandin synthesis) can be used for individualized tocolytic treatment. Premature rupture of the membranes is an indication for antibiotics.

CONCLUSION

The goal of all attempts to prevent and treat preterm labor is to improve preterm infants' chances of surviving with as few complications as possible. The methods discussed here can be used to prolong pregnancies at risk for preterm labor and so to reduce perinatal morbidity and mortality.

Comparison of the mechanisms responsible for cervical remodeling in preterm and term labor

Understanding the mechanisms of term and preterm cervical remodeling is essential to prevent prematurity. Is preterm cervical remodeling caused by the same mechanisms that cause cervical remodeling at term, and are these changes accelerated in time? This question has been pondered by obstetricians seeking strategies to prevent preterm labor for many years. Mice represent an informative model of preterm birth. Thus, in this review we discuss the recent findings from mouse models that identify and characterize the initiators and cellular effectors of cervical remodeling at term and preterm labor/delivery. These studies suggest that similarities and differences exist between term and preterm cervical remodeling. Complement is an initiator or mediator in preterm labor/delivery, but is not involved in the physiological process that leads to term delivery. Therefore, complememt constitutes a specific and selective target for potentially preventing preterm delivery, thus improving neonatal health.

Oral betamimetics for maintenance therapy after threatened preterm labour

BACKGROUND

Some women who have threatened to give birth prematurely, subsequently settle. They may then take oral tocolytic maintenance therapy to prevent preterm birth and to prolong gestation.

OBJECTIVES

To assess the effects of oral betamimetic maintenance therapy after threatened preterm labour for preventing preterm birth.

SEARCH METHODS

We updated the search of the Cochrane Pregnancy and Childbirth Group's Trials Register on 9 November 2012.

SELECTION CRITERIA

Randomised controlled trials comparing oral betamimetic with alternative tocolytic therapy, placebo or no therapy, for maintenance following treatment of threatened preterm labour.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies.

MAIN RESULTS

We did not identify any new trials from the updated search so the results remain unchanged as follows.We included 13 randomised controlled trials (RCTs) with a total of 1551 women. We found no differences for admission to the neonatal intensive care unit when betamimetics were compared with placebo (risk ratio (RR) 1.28, 95% confidence interval (CI) 0.68 to 2.41; two RCTs of terbutaline with 2600 women) or with magnesium (RR 0.80, 95% CI 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks) showed no significant difference in six RCTs, four comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.11, 95% CI 0.91 to 1.35; 644 women). We observed no differences between betamimetics and placebo, no treatment or other tocolytics for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than the groups allocated to placebo, no treatment or another type of tocolytic.

AUTHORS' CONCLUSIONS

Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labour.

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.

Prophylactic oral betamimetics for reducing preterm birth in women with a twin pregnancy

BACKGROUND

Twin pregnancies are associated with a high risk of neonatal mortality and morbidity due to an increased rate of preterm birth. Betamimetics can decrease contraction frequency or delay preterm birth in singleton pregnancies by 24 to 48 hours. The efficacy of oral betamimetics in women with a twin pregnancy is unproven.

OBJECTIVES

To assess the effectiveness of prophylactic oral betamimetics for the prevention of preterm labour and birth for women with twin pregnancies.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group Trials Register (31 January 2012), the Central Register of Controlled Trials (The Cochrane Library 2012, Issue 2), MEDLINE (January 1966 to 1 February 2012) and EMBASE (January 1985 to 1 February 2012).

SELECTION CRITERIA

Randomised controlled trials in twin pregnancies comparing oral betamimetics with placebo or any intervention with the specific aim of preventing preterm birth. Quasi-randomised controlled trials, cluster-randomised trials and cross-over trials were not included.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and trial quality. Two review authors extracted data. Data were checked for accuracy.

MAIN RESULTS

Six trials (374 twin pregnancies) were included, but only five trials (344 twin pregnancies) contributed data. All trials compared oral betamimetics with placebo.Betamimetics reduced the incidence of preterm labour (one trial, 50 twin pregnancies, risk ratio (RR) 0.40; 95% confidence interval (CI) 0.19 to 0.86). However, betamimetics did not reduce preterm birth less than 37 weeks' gestation (four trials, 276 twin pregnancies, RR 0.85; 95% CI 0.65 to 1.10) or less than 34 weeks' gestation (one trial, 144 twin pregnancies, RR 0.47; 95% CI 0.15 to 1.50). Mean neonatal birthweight in the betamimetic group was significantly higher than in the placebo group (three trials, 478 neonates, mean difference 111.22 g; 95% CI 22.2 to 200.2). Nevertheless, there was no evidence of an effect of betamimetics in reduction of low birthweight (two trials, 366 neonates, average RR 1.19; 95% CI 0.77 to 1.85, random-effects) or small-for-gestational age neonates (two trials, 178 neonates, RR 0.92; 95% CI 0.52 to 1.65). Two trials (388 neonates) showed that betamimetics significantly reduced the incidence of respiratory distress syndrome but the difference was not significant when the analysis was adjusted for correlation of babies from twins. Three trials (452 neonates) showed no evidence of an effect of betamimetics in reducing neonatal mortality (RR 0.80; 95% CI 0.35 to 1.82).

AUTHORS' CONCLUSIONS

There is insufficient evidence to support or refute the use of prophylactic oral betamimetics for preventing preterm birth in women with a twin pregnancy.

Home uterine monitoring for detecting preterm labour

BACKGROUND

To reduce the morbidity and mortality associated with preterm birth, home uterine activity monitoring aims for early detection of increased contraction frequency, and early intervention with tocolytic drugs to inhibit labour and prolong pregnancy. However, the effectiveness of such monitoring is disputed.

OBJECTIVES

To determine whether home uterine activity monitoring is effective in improving the outcomes for women and their infants considered to be at high risk of preterm birth, when compared with conventional or other care packages that do not include home uterine monitoring.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 November 2011), CENTRAL (The Cochrane Library 2011, Issue 4 of 4), MEDLINE (1966 to 30 November 2011), EMBASE (1974 to 30 November 2011), CINAHL (1982 to 30 November 2011) and scanned reference lists of retrieved studies.

SELECTION CRITERIA

Randomised control trials of home uterine activity monitoring, with or without patient education programmes, for women at risk for preterm birth, in comparison to the same care package without home uterine activity monitoring.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion, extracted data and assessed risk of bias. Data were checked for accuracy. We did not attempt to contact authors to resolve queries.

MAIN RESULTS

There were 15 included studies (total number of enrolled participants 6008); 13 studies contributed data. Women using home uterine monitoring were less likely to experience preterm birth at less than 34 weeks (risk ratio (RR) 0.78; 95% confidence interval (CI) 0.62 to 0.99; three studies, n = 1596; fixed-effect analysis). However, this significant difference was not evident when we carried out a sensitivity analysis, restricting the analysis to studies at low risk of bias based on study quality (RR 0.75; 95% CI 0.57 to 1.00, one study, 1292 women). There was no significant difference in the rate of perinatal mortality (RR 1.22; 95% CI 0.86 to 1.72; two studies, n = 2589).There was no significant difference in the number of preterm births at less than 37 weeks (average RR 0.85; CI 0.72 to 1.01; eight studies, n = 4834; random effects, T(2) = 0.03, I(2) = 68%). Infants born to women using home uterine monitoring were less likely to be admitted to neonatal intensive care unit (average RR 0.77; 95% CI 0.62 to 0.96; five studies, n = 2367; random-effects, T(2) = 0.02, I(2) = 32%). Although this difference was not statistically significant when only high quality studies were included (RR 0.86; 95% CI 0.74 to 1.01; one study, n = 1292). Women using home uterine monitoring made more unscheduled antenatal visits (mean difference (MD) 0.49; 95% CI 0.39 to 0.62; two studies, n = 2807). Women using home uterine monitoring were also more likely to have prophylactic tocolytic drug therapy (average RR 1.21; 95% CI 1.01 to 1.45; seven studies, n = 4316; random-effects. T(2) = 0.03, I(2) = 62%) but this difference was no longer significant when the analysis was restricted to high quality studies (average RR 1.22; 95% CI 0.90 to 1.65, three studies, n = 3749,random effects, T(2) = 0.05, I(2) = 76%). One small study reported that the home uterine monitoring group spent fewer days in hospital antenatally. No data on maternal anxiety or acceptability were found.

AUTHORS' CONCLUSIONS

Home uterine monitoring may result in fewer admissions to a neonatal intensive care unit but more unscheduled antenatal visits and tocolytic treatment. There is no impact on maternal and perinatal outcomes such as perinatal mortality or incidence of preterm birth.

Tocolytic therapy for acute preterm labor

The pathophysiology leading to preterm labor is not well understood and often multifactorial; initiating factors include intrauterine infection, inflammation, ischemia, overdistension, and hemorrhage. Given these different potential causes, directing therapy for preterm labor has been difficult and suboptimal. To date, no single drug has been identified as successful in treating all of the underlying mechanisms leading to preterm labor. In addition, the methodology of many of the tocolytic studies is limited by lack of sufficient patient numbers, lack of comparison with a placebo, and inconsistent use of glucocorticoids. The limitations in these individual studies make it difficult to evaluate the efficacy of a single tocolytic by meta-analysis. Despite these limitations, the goals for tocolysis for preterm labor are clear: To complete a course of glucocorticoids and secure the appropriate level of neonatal care for the fetus in the event of preterm delivery. The literature demonstrates that many tocolytic agents inhibit uterine contractility. The decision as to which tocolytic agent should be used as first-line therapy for a patient is based on multiple factors, including gestational age, the patient’s medical history, common and severe side effects, and a patient’s response to therapy. In a patient at less than 32 weeks gestation, indomethacin may be a reasonable first choice based on its efficacy, ease of administration, and minimal side effects. Concurrent administration of magnesium for neuroprotection may be given. At 32 to 34 weeks, nifedipine may be a reasonable first choice because it does not carry the fetal risks of indomethacin at these later gestational ages, is easy to administer, and has limited side effects relative to beta-mimetics. In an effort to review a commonly faced obstetrical complication, this article has provided a summary of the most commonly used tocolytics, their mechanisms of action, side effects, and clinical data regarding their efficacy.

Prevention of preterm labour: 2011 update on tocolysis

The aim of this paper is to review available data about drugs for preventing preterm labour. Tocolytic therapy includes β adrenergic receptor agonists, NO donors, magnesium sulphate, prostaglandin-synthase inhibitors, oxytocin receptor antagonists, calcium-channel blockers, progesterone, 17-α-hydroxyprogesterone caproate, and antibiotics. Their specific effects on myometrial contractility, their safety, their efficiency, and side effects profile for the mother and the fetus are presented. The main question of why and for what reasons tocolysis should be administrated is discussed.

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.

The effectiveness of medical interventions aimed at preventing preterm birth: a literature review

BACKGROUND

Preterm birth is a significant global health problem with serious short and long term consequences. This paper reviews the research literature to answer the question how effective are the medical interventions that aim to reduce the rates of preterm birth?

METHODS

A systematic search was carried out in CINAHL, Cochrane, Medline and Embase in relation to following medical treatments aimed at preventing preterm births: anti-infective medications, tocolytics, progesterone and cervical cerclage. The research underpinning each type of intervention is critically analysed in order to establish the validity of knowledge claims that are made for each type of intervention.

FINDINGS

In relation to reducing the rates of preterm births, anti-infectives are only effective in the presence of known infection. Screening for infections during pregnancy is ineffective. Tocolytic agents are not effective in decreasing the preterm birth rates. Progesterone seems to be effective in a select group of pregnant women at higher risk of preterm birth. Cervical cerclage plays a small and an occasional role in preventing some preterm births.

CONCLUSIONS

This literature review demonstrates that medical interventions aimed at preventing, not just delaying, preterm birth, are not effective at a population level. Providing holistic, antenatal midwifery care for women living in socio-economic disadvantage and/or with an increased risk of preterm birth seems to be a promising strategy to address the negative effects of the social determinants of disease and thus to reduce the rate of preterm births at an individual and a population level.

Nifedipine in the management of preterm labor: a systematic review and metaanalysis

OBJECTIVE

To determine the efficacy and safety of nifedipine as a tocolytic agent in women with preterm labor.

STUDY DESIGN

A systematic review and metaanalysis of randomized controlled trials.

RESULTS

Twenty-six trials (2179 women) were included. Nifedipine was associated with a significant reduction in the risk of delivery within 7 days of initiation of treatment and before 34 weeks' gestation, respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage, neonatal jaundice, and admission to the neonatal intensive care unit when compared with β₂-adrenergic-receptor agonists. There was no difference between nifedipine and magnesium sulfate in tocolytic efficacy. Nifedipine was associated with significantly fewer maternal adverse events than β₂-adrenergic-receptor agonists and magnesium sulfate. Maintenance nifedipine tocolysis was ineffective in prolonging gestation or improving neonatal outcomes when compared with placebo or no treatment.

CONCLUSION

Nifedipine is superior to β₂-adrenergic-receptor agonists and magnesium sulfate for tocolysis in women with preterm labor.

Twins: prevalence, problems, and preterm births

The rate of twin pregnancies in the United States has stabilized at 32 per 1000 births in 2006. Aside from determining chorionicity, first-trimester screening and second-trimester ultrasound scanning should ascertain whether there are structural or chromosomal abnormalities. Compared with singleton births, genetic amniocentesis-related loss at <24 weeks of gestation for twin births is higher (0.9% vs 2.9%, respectively). Selective termination for an anomalous fetus is an option, although the pregnancy loss rate is 7% at experienced centers. For singleton and twin births for African American and white women, approximately 50% of preterm births are indicated; approximately one-third of these births are spontaneous, and 10% of the births occur after preterm premature rupture of membranes. From 1989-2000, the rate of preterm twin births increased, for African American and white women alike, although the perinatal mortality rate has actually decreased. As with singleton births, tocolytics should be used judiciously and only for a limited time (<48 hours) in twin births. Administration of antenatal corticosteroids is an evidence-based recommendation.