Efficacy of maintenance therapy after acute tocolysis: a meta-analysis

Maintaining and repeating tocolysis: A reflection on evidence

It is inherent to human logic that both doctors and patients want to suppress uterine contractions when a woman presents in threatened preterm labor. Tocolysis is widely applied in women with threatened preterm labor with a variety of drugs. According to literature, tocolysis is indicated to enable transfer to a tertiary center as well as to ensure the administration of corticosteroids for fetal maturation. There is international discrepancy in the content and the implementation of guidelines on preterm labor. Tocolysis is often maintained or repeated. Nevertheless, the benefit of prolonging pregnancy has not yet been proven, and it is not impossible that prolongation of the pregnancy in a potential hostile environment could harm the fetus. Here we reflect on the use of tocolysis, focusing on maintenance and repeated tocolysis, and compare international guidelines and practices to available evidence. Finally, we propose strategies to improve the evaluation and use of tocolytics, with potential implications for future research.

Effectiveness of the contemporary treatment of preterm labor: a comparison with a historical cohort

OBJECTIVE

To compare the effectiveness of contemporary treatment of preterm labor to a historical cohort.

STUDY DESIGN

Retrospective matched case-control study to compare the outcomes of patients that were treated for preterm labor at the University Hospital of Tuebingen, Germany in 2014/2015 (current treatment cohort) and 2006/2007 (historical cohort). The study included women with singleton gestations who were admitted with the diagnosis of preterm labor between 24 + 0 and 34 + 0 weeks' gestation and a cervical length of ≤15 mm. Women in the historical cohort were hospitalized until either 34 weeks' gestation or until complete cessation of uterine contractions. They were treated with intravenous beta-mimetics continuously, received antibiotics based on the vaginal culture and corticosteroids regardless of cervical length measurement. Bed rest was always recommended. The current treatment cohort was tocolyzed with an oral calcium channel blocker for approximately 3 days followed by vaginal progesterone until 34 weeks' gestation. Corticosteroids were given only if the cervical length is ≤15 mm. Bed rest was not recommended.

RESULTS

The study population consisted of 110 pregnancies, 55 in the historical cohort and 55 in the current treatment cohort. At the time of admission, mean gestational age in both groups was 29.3 and 29.7 weeks. In the historical and current treatment cohort the length of the hospitalization was 24.0 and 5.5 days and tocolysis was given for 19.5 and 3.4 days, respectively. In the historical cohort, mean gestational age at delivery was 35.6 weeks. In 63.6% cases delivery occurred prior to 37 weeks. In the current treatment group mean gestational age at the delivery was 37.0 weeks and 36.4% were delivered prior to 37 weeks.

CONCLUSION

Short-term hospitalization and tocolysis followed by vaginal progesterone for maintenance tocolysis is more effective than a protocol which includes long-term hospital stay, beta-mimetics, antibiotics, and bed rest.

Does magnesium sulfate delay the active phase of labor in women with premature rupture of membranes? A randomized controlled trial

OBJECTIVE

Administration of many drugs including magnesium sulfate (MS) has considerable influences on pregnancy outcomes. The present study investigates the effects of MS administration on reaching the active phase of labor in women with premature rupture of membrane (PROM) and subsequent fetal complications.

MATERIALS AND METHODS

A double blind, randomized, placebo-controlled trial was performed among primipara women referred to the PROM center in Tehran, Iran between March 2010 and August 2012. Patients were equally allocated into two groups; the intervention group who received MS (n = 46) and the control (placebo) group (n = 46). Both groups received a corticosteroid, 1g oral azithromycin (oral) and 2 g ampicillin (IV) every 6 hours for 48 hours, followed by amoxicillin (500 mg orally 3 times daily) for an additional 5 days. None of the research staff were aware of the treatment allocation of patients in order for blinding purposes.

RESULTS

Administration of MS in intervention group increases this period 2.7 times compared to the control group. In women whose gestational age was <30 weeks, MS administration increased the active phase of labor up to 77%. Administration of magnesium sulfate reduced the risk of respiratory distress syndrome significantly (p = 0 .002), without producing any adverse pregnancy outcomes.

CONCLUSION

Magnesium sulfate increases delay in reaching the active phase of labor in mothers with PROM, without producing adverse birth outcomes. (Registration ID in IRCT; IRCT2012091810876N1).

Cyclo-oxygenase (COX) inhibitors for treating preterm labour

BACKGROUND

Preterm birth is a major cause of perinatal mortality and morbidity. Cyclo-oxygenase (COX) inhibitors inhibit uterine contractions, are easily administered and appear to have few maternal side effects. However, adverse effects have been reported in the fetus and newborn as a result of exposure to COX inhibitors.

OBJECTIVES

To assess the effects on maternal and neonatal outcomes of COX inhibitors administered as a tocolytic agent to women in preterm labour when compared with (i) placebo or no intervention and (ii) other tocolytics. In addition, to compare the effects of non-selective COX inhibitors with COX-2 selective inhibitors.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (24 August 2014). We also contacted recognised experts and searched reference lists of retrieved studies.

SELECTION CRITERIA

All published and unpublished randomised trials in which COX inhibitors were used for tocolysis for women in labour between 20 and 36 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated methodological quality and extracted data. We sought additional information from study authors. Results are presented using risk ratio (RR; dichotomous data) and mean difference (MD; continuous data) with 95% confidence interval (CI). The number needed to treat for benefit (NNTB) and the number needed to treat for harm (NNTH) were calculated for statistically different categorical outcomes.

MAIN RESULTS

With the addition of seven studies with a total of 684 women, this review now includes outcome data from 20 studies including 1509 women. The non-selective COX inhibitor indomethacin was used in 15 studies. The overall quality of the included studies was considered moderate to low.Three small studies (102 women), two of which were conducted in the 1980's, compared COX inhibition (indomethacin only) with placebo. No difference was shown in birth less than 48 hours after trial entry (average RR 0.20, 95% CI 0.03 to 1.28; two studies with 70 women). Indomethacin resulted in a reduction in preterm birth (before completion of 37 weeks of gestation) in one small study (36 women) (RR 0.21, 95% CI 0.07 to 0.62; NNTB 2, 95% CI 2 to 4); and an increase in gestational age at birth (average MD 3.59 weeks, 95% CI 0.65 to 6.52; two studies with 66 women) and birthweight (MD 716.34 g, 95% CI 425.52 to 1007.16; two studies with 67 infants). No difference was shown in measures of neonatal morbidity or neonatal mortality.Compared with betamimetics, COX inhibitors resulted in a reduction in birth less than 48 hours after trial entry (RR 0.27, 95% CI 0.08 to 0.96; NNTB 7, 95% CI 6 to 120; two studies with 100 women) and preterm birth (before completion of 37 weeks of gestation) (RR 0.53, 95% CI 0.28 to 0.99; NNTB 6, 95% CI 4 to 236; two studies with 80 women) although no benefit was shown in terms of neonatal morbidity or mortality. COX inhibition was also associated with fewer maternal adverse affects compared with betamimetics (RR 0.19, 95% CI 0.11 to 0.31; NNTB 3, 95% CI 2 to 3; five studies with 248 women) and maternal adverse effects requiring cessation of treatment (average RR 0.09, 95% CI 0.02 to 0.49; NNTB 5, CI 95% 5 to 9; three studies with 166 women).No differences were shown when comparing COX inhibitors with magnesium sulphate (MgSO4) (seven studies with 792 women) or calcium channel blockers (CCBs) (two studies with 230 women) in terms of prolonging pregnancy or for any fetal/neonatal outcomes. There were also no differences in very preterm birth (before completion of 34 weeks of gestation) and no maternal deaths occurred in the one study that reported on this outcome. However COX inhibitors resulted in fewer maternal adverse affects when compared with MgSO4 (RR 0.39, 95% CI 0.25 to 0.62; NNTB 11, 95% CI 9 to 17; five studies with 635 women).A comparison of non-selective COX inhibitors versus any COX-2 inhibitor (two studies with 54 women) did not demonstrate any differences in maternal, fetal or neonatal outcomes.No data were available to assess COX inhibitors compared with oxytocin receptor antagonists (ORAs). Further, no data were available on extremely preterm birth (before 28 weeks of gestation), longer-term infant outcomes or costs.

AUTHORS' CONCLUSIONS

In this review, no clear benefit for COX inhibitors was shown over placebo or any other tocolytic agents. While some benefit was demonstrated in terms of postponement of birth for COX inhibitors over placebo and betamimetics and also maternal adverse effects over betamimetics and MgSO4, due to the limitations of small numbers, minimal data on safety, lack of longer-term outcomes and generally low quality of the studies included in this review, we conclude that there is insufficient evidence on which to base decisions about the role of COX inhibition for women in preterm labour. Further well-designed tocolytic studies are required to determine short- and longer-term infant benefit of COX inhibitors over placebo and other tocolytics, particularly CCBs and ORAs. Another important focus for future studies is identifying whether COX-2 inhibitors are superior to non-selective COX inhibitors. All future studies on tocolytics for women in preterm labour should assess longer-term effects into early childhood and also costs.

Treatment of spontaneous preterm labour with retosiban: a phase 2 proof-of-concept study

AIM

The aim was to investigate the efficacy and safety of intravenous retosiban in women with spontaneous preterm labour.

METHODS

This was a randomized, double-blind, placebo-controlled, phase 2 trial. Retosiban was administered intravenously for 48 h to women in spontaneous preterm labour between 30(0/7) and 35(6/7)  weeks' gestation with an uncomplicated singleton pregnancy in an in-patient obstetric unit. Outcome measures were uterine quiescence (primary endpoint), days to delivery, preterm delivery and safety.

RESULTS

Uterine quiescence was achieved in 62% of women who received retosiban (n = 30) compared with 41% who received placebo (n = 34). The relative risk (RR) was 1.53 (95% credible interval [CrI] 0.98, 2.48; NS). Retosiban resulted in a significant increase in time to delivery compared with placebo (mean difference 8.2 days, 95% CrI 2.7, 13.74). This difference was consistent across all gestational ages. The proportion of preterm births in the retosiban and placebo groups was 18.7% (95% CrI 7.4%, 33.7%) and 47.2% (95% CrI 31.4%, 63.4%), respectively. The RR of preterm birth in women treated with retosiban was 0.38 (95% CrI 0.15, 0.81). There were no deliveries within 7 days in the retosiban group, but there were six (17.6%) births in the placebo group. The maternal, fetal and neonatal adverse events were comparable in the retosiban and placebo groups.

CONCLUSIONS

Intravenous administration of retosiban in women with spontaneous preterm labour was associated with a greater than 1 week increase in time to delivery compared with placebo, a significant reduction in preterm deliveries, a non-significant increase in uterine quiescence and a favourable safety profile.

Terbutaline and Associated Risks for Neurodevelopmental Disorders

Preterm labor often leads to a preterm birth and has been shown to be the most important determinant of risk for perinatal morbidity and mortality. While medication management has been utilized by physicians to delay preterm labor, the results these medications achieve remain inconsistent, in addition to increasing the risk to the developing fetus. Terbutaline has been among the most commonly used β2-adrenoreceptor (β2AR) agonists in the management of preterm labor. The research suggests that tocolytic terbutaline therapy carries a significant risk for the mother and the child, which can be magnified by extended exposure, sex of the fetus, and administration during critical fetal developmental periods. This paper highlights the research on terbutaline in treatment of preterm labor, along with the possible associated cognitive deficits in adolescents who were treated with terbutaline in utero. Two case summaries are presented to illustrate the potential deficits in clinical presentations of adolescents with history of intrauterine exposure to terbutaline. Publicizing the association between terbutaline and these deficits can not only assist obstetricians and expectant mothers in making a more informed choice in the treatment of preterm labor but also provide neuropsychologists and pediatricians with information helpful in understanding the etiology of these impairments.

A novel molecular microbiologic technique for the rapid diagnosis of microbial invasion of the amniotic cavity and intra-amniotic infection in preterm labor with intact membranes

PROBLEM

The diagnosis of microbial invasion of the amniotic cavity (MIAC) has been traditionally performed using traditional cultivation techniques, which require growth of microorganisms in the laboratory. Shortcomings of culture methods include the time required (days) for identification of microorganisms, and that many microbes involved in the genesis of human diseases are difficult to culture. A novel technique combines broad-range real-time polymerase chain reaction with electrospray ionization time-of-flight mass spectrometry (PCR/ESI-MS) to identify and quantify genomic material from bacteria and viruses.

METHOD OF STUDY

AF samples obtained by transabdominal amniocentesis from 142 women with preterm labor and intact membranes (PTL) were analyzed using cultivation techniques (aerobic, anaerobic, and genital mycoplasmas) as well as PCR/ESI-MS. The prevalence and relative magnitude of intra-amniotic inflammation [AF interleukin 6 (IL-6) concentration ≥ 2.6 ng/mL], acute histologic chorioamnionitis, spontaneous preterm delivery, and perinatal mortality were examined.

RESULTS

(i) The prevalence of MIAC in patients with PTL was 7% using standard cultivation techniques and 12% using PCR/ESI-MS; (ii) seven of ten patients with positive AF culture also had positive PCR/ESI-MS [≥17 genome equivalents per PCR reaction well (GE/well)]; (iii) patients with positive PCR/ESI-MS (≥17 GE/well) and negative AF cultures had significantly higher rates of intra-amniotic inflammation and acute histologic chorioamnionitis, a shorter interval to delivery [median (interquartile range-IQR)], and offspring at higher risk of perinatal mortality, than women with both tests negative [90% (9/10) versus 32% (39/122) OR: 5.6; 95% CI: 1.4-22; (P < 0.001); 70% (7/10) versus 35% (39/112); (P = 0.04); 1 (IQR: <1-2) days versus 25 (IQR: 5-51) days; (P = 0.002), respectively]; (iv) there were no significant differences in these outcomes between patients with positive PCR/ESI-MS (≥17 GE/well) who had negative AF cultures and those with positive AF cultures; and (v) PCR/ESI-MS detected genomic material from viruses in two patients (1.4%).

CONCLUSION

(i) Rapid diagnosis of intra-amniotic infection is possible using PCR/ESI-MS; (ii) the combined use of biomarkers of inflammation and PCR/ESI-MS allows for the identification of specific bacteria and viruses in women with preterm labor and intra-amniotic infection; and (iii) this approach may allow for administration of timely and specific interventions to reduce morbidity attributed to infection-induced preterm birth.

Maintenance therapy with calcium channel blockers for preventing preterm birth after threatened preterm labour

BACKGROUND

Calcium channel blocker maintenance therapy is one of the types of tocolytic therapy that may be used after an episode of threatened preterm labour (and usually an initial dose of tocolytic therapy) in an attempt to prevent the onset of further preterm contractions.

OBJECTIVES

To assess the effects of calcium channel blockers as maintenance therapy on preventing preterm birth after threatened preterm labour.

SEARCH METHODS

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

SELECTION CRITERIA

Randomised controlled trials of calcium channel blockers used as maintenance therapy to prevent preterm birth after threatened preterm labour, compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of included studies.

MAIN RESULTS

We included six trials that enrolled 794 women and their babies and all assessed nifedipine as calcium channel blocker maintenance therapy. The six trials were judged to be at a moderate risk of bias overall. No differences in the incidence of preterm birth (risk ratio (RR) 0.97; 95% confidence interval (CI) 0.87 to 1.09; five trials, 681 women), birth within 48 hours of treatment (RR 0.46; 95% CI 0.07 to 3.00; two trials, 128 women) or neonatal mortality (average RR 0.75; 95% CI 0.05 to 11.76; two trials, 133 infants) were seen when nifedipine maintenance therapy was compared with placebo or no treatment. No stillbirths were reported in the one trial that provided data for this outcome. No trials reported on longer-term follow-up of infants.Women receiving nifedipine maintenance therapy were significantly more likely to have their pregnancy prolonged (mean difference (MD) 5.35 days; 95% CI 0.49 to 10.21; four trials, 275 women); however, no differences between groups were shown for birth at less than 34 weeks' gestation, birth at less than 28 weeks' gestation, birth within seven days of treatment, or gestational age at birth. No significant differences were shown between the nifedipine and control groups for any of the secondary neonatal morbidities reported. Similarly, no significant differences were seen for the outcomes relating to the use of health services, except for in one trial, where infants whose mothers received nifedipine were significantly more likely to have a longer length of hospital stay as compared with infants born to mothers who received a placebo (MD 14.00 days; 95% CI 4.21 to 23.79; 60 infants).

AUTHORS' CONCLUSIONS

Based on the current available evidence, maintenance treatment with a calcium channel blocker after threatened preterm labour does not prevent preterm birth or improve maternal or infant outcomes.

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.

Individual and organisational determinants associated with maintenance tocolysis in the management of preterm labour: a multilevel analysis

Background

Clinical guidelines do not recommend maintenance tocolysis for the management of preterm labour. The French national survey EVAPRIMA revealed it was administered to more than 50% of women hospitalised for preterm labour. Our aim was to identify the individual and organisational determinants associated with maintenance tocolysis.

Methods

The study was a secondary analysis of the prospective population-based EVAPRIMA study database. Population study included every women hospitalised for preterm labour and at risk of receiving maintenance tocolysis, over a one month period, in 99 randomly selected French maternity units. Main outcome was the prescription of maintenance tocolysis. The association between maintenance tocolysis and individual (maternal or obstetrical) and organisational determinants were evaluated with multilevel analysis.

Results

Of the 531 women included, 68.9% (95% CI 0.65–0.73) received maintenance tocolysis. The only individual factor associated with maintenance tocolysis was gestational age at admission; the rate of maintenance tocolysis was higher among women hospitalised before 32 weeks of gestation. The significantly different rates between maternity units demonstrated the existence of a maternity unit effect. Maintenance tocolysis was also associated with organisational determinants and was more frequent in level 1 (ORa = 6.54[2.21–19.40]) and level 2 maternity units (ORa = 3.68[1.28–10.59]), in units with less than 1500 deliveries/year (ORa = 5.27[4.43–19.44]), and in specific areas of France.

Conclusion

A maternity unit effect, explained partly by the organisational characteristics of the units, plays a major role in the practice of maintenance tocolysis. Widespread dissemination of these results might improve adherence to clinical guidelines.

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.

Prevention of preterm delivery after successful tocolysis in preterm labor by 17 alpha-hydroxyprogesterone caproate: a randomized controlled trial

OBJECTIVE

The objective of the study was to evaluate the use of 17 alpha-hydroxyprogesterone caproate (17P) to reduce preterm delivery.

STUDY DESIGN

This open-label, multicenter, randomized controlled trial included women with singleton pregnancies admitted at 24-31 weeks' gestation and cervical length less than 25 mm for preterm labor successfully arrested by tocolytic treatment. Randomization assigned them to receive (or not) 500 mg of intramuscular 17P after tocolysis ended, repeated semiweekly until 36 weeks or preterm delivery. The primary outcome was the time from randomization to delivery.

RESULTS

Outcome data were available for 184 of 188 women randomized. The 17P and control groups (similar for most baseline characteristics) did not differ significantly for median [interquartile range] time to delivery (64 [42-79] and 67 [46-83] days, respectively) or rates of delivery before 37, 34, or 32 weeks of gestation or adverse perinatal outcomes.

CONCLUSION

Semiweekly injections of 17P did not prolong pregnancy significantly in women with tocolysis-arrested preterm labor.

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 STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (May 2010).

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, which recruited 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 (2 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 also compared with alternative treatments, was 5.00, 95% CI 0.25 to 99.16 (one trial, 50 infants). Women taking magnesium preparations were less likely to report palpitations or tachycardia than women receiving alternative therapies (RR 0.26, 95% CI 0.13 to 0.52, three trials, 237 women) but were much more likely to experience diarrhoea (RR 7.66, 95% CI 2.18 to 26.98, 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.

Assessment of perinatal outcome after sustained tocolysis in early labour (APOSTEL-II trial)

Background

Preterm labour is the main cause of perinatal morbidity and mortality in the Western world. At present, there is evidence that tocolysis for 48 hours is useful in women with threatened preterm labour at least before 32 weeks. This allows transfer of the patient to a perinatal centre, and maximizes the effect of corticosteroids for improved neonatal survival. It is questionable whether treatment with tocolytics should be maintained after 48 hours.

Methods/Design

The APOSTEL II trial is a multicentre placebo-controlled study. Pregnant women admitted for threatened preterm labour who have been treated with 48 hours corticosteroids and tocolysis will be eligible to participate in the trial between 26⁺⁰ and 32⁺² weeks gestational age. They will be randomly allocated to nifedipine (intervention) or placebo (control) for twelve days or until delivery, whatever comes first.

Primary outcome is a composite of perinatal death, and severe neonatal morbidity up to evaluation at 6 months after birth. Secondary outcomes are gestational age at delivery, number of days in neonatal intensive care and total days of the first 6 months out of hospital. In addition a cost-effectiveness analysis will be performed. Analysis will be by intention to treat. The power calculation is based on an expected 11% difference in adverse neonatal outcome. This implies that 406 women have to be randomised (two sided test, β 0.2 at alpha 0.05).

Discussion

This trial will provide evidence as to whether maintenance tocolysis reduces severe perinatal morbidity and mortality in women with threatened preterm labour before 32 weeks.

Trial Registration

Clinical trial registration: , NTR 1336, date of registration: June 3^rd 2008.

Maintenance nifedipine tocolysis compared with placebo: a randomized controlled trial

OBJECTIVE

To estimate whether maintenance nifedipine tocolysis after arrested preterm labor prolongs pregnancy and improves neonatal outcomes.

METHODS

A prospective, randomized double-blind, multicenter study was conducted. After successful tocolysis, patients were randomly assigned to receive 20 mg nifedipine or an identical-appearing placebo every 4-6 hours until 37 weeks of gestation. The primary outcome was attainment of 37 weeks of gestation. Patients were enrolled between 24 weeks and 34 weeks if they had six or fewer contractions per hour, intact membranes, and less than 4 cm cervical dilation. Exclusion criteria were placental abruption or previa, fetal anomaly incompatible with life, or maternal medical contraindication to tocolysis. Sixty-six patients were required for 80% power to detect a 50% reduction in birth before 37 weeks, with a two-tailed alpha of 0.05. Data were analyzed by intent to treat.

RESULTS

Seventy-one patients were randomly assigned. Two patients were excluded after randomization and one was lost to follow-up. Thirty-five patients received placebo, and 33 received nifedipine. There were no maternal demographic differences between groups; the placebo group was significantly more dilated and effaced at study entry. There was no difference in attainment of 37 weeks (39% nifedipine compared with 37% placebo, P>.91), mean delay of delivery (33.5+/-19.9 days nifedipine compared with 32.6+/-21.4 days placebo, P=.81) or delay of delivery for greater than 48 hours or 1, 2, 3, or 4 weeks. Neonatal outcomes were similar between groups.

CONCLUSION

When compared with placebo, maintenance nifedipine tocolysis did not confer a large reduction in preterm birth or improvement in neonatal outcomes.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, www.clinicaltrials.gov, NCT00185952

LEVEL OF EVIDENCE

I.

Progesterone for maintenance tocolytic therapy after threatened preterm labour: a randomised controlled trial

BACKGROUND

Women with preterm labour that is arrested with tocolytic therapy are at increased risk of recurrent preterm labour. The efficacy of maintenance tocolytic therapy after successful arrest of preterm labour remains controversial.

AIM

The purpose of this study was to determine whether supplementation of vaginal progesterone after inhibition of preterm labour is associated with an increased latency period and a decreased recurrent of preterm labour.

METHODS

This trial was conducted in 70 women who presented with symptoms of threatened preterm labour, who after arrest of uterine activity were then randomised to progesterone therapy or no treatment. Treatment group received progesterone suppository (400 mg) daily until delivery and control group received no treatment.

RESULTS

Longer mean latency until delivery (36/11 +/- 17/9 vs 24/52 +/- 27/2) (mean + standard deviation) days; respiratory distress syndrome 4 (10.8%) vs 12 (36.4%) P = 0.021; low birthweight 10 (27%) vs 17 (51.5%) P = 0.04; and birthweight (3101.54 +/- 587.9 g vs r 2609.39 +/- 662.9 g, P = 0.002), were significantly different between the two groups. No significant differences were found between recurrent preterm labour 13 (35.1%) vs 19 (57.6%), P = 0.092; admission to intensive care unit 9 (24.3%) vs 13 (39.4%), P= 0.205 ; and neonatal sepsis 2 (5.4%) vs 6 (18.2%) P = 0.136, for the progesterone and control groups, respectively.

CONCLUSION

The use of vaginal progesterone suppository after successful parenteral tocolysis associated with a longer latency preceding delivery but failed to reduce the incidence of readmission for preterm labour.

The present and future of tocolysis

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

Guidelines for the management of spontaneous preterm labor

Preterm birth is defined as delivery at <37 completed weeks of pregnancy (World Health Organization). Spontaneous preterm birth (SPB) includes preterm labor, preterm spontaneous rupture of membranes, preterm premature rupture of membranes (PPROM) and cervical weakness; it does not include indicated preterm delivery for maternal or fetal conditions. Early SPB (<32 weeks' gestation) is associated with an increased higher perinatal mortality rate, inversely proportional to gestational age. The pathophysiologic events that trigger SPB are largely unknown but include decidual hemorrhage (abruption), mechanical factors (uterine overdistention or cervical incompetence), and hormonal changes (perhaps mediated by fetal or maternal stress). In addition, several cervicovaginal infections have been associated with preterm labor. SPB is also the leading cause of long-term morbidity, including neurodevelopmental handicap, cerebral palsy, seizure disorders, blindness, deafness and non-neurological disorders, such as bronchopulmonary dysplasia and retinopathy of prematurity. Delaying delivery may reduce the rate of long-term morbidity by facilitating the maturation of developing organs and systems. The benefits of administration of antepartum glucocorticosteroids to reduce the incidence and severity of respiratory distress syndrome may be exploited by delay. Delay may also permit transfer of the fetus in utero to a center with neonatal intensive care unit facilities. There is considerable variation in the way that spontaneous preterm labor (SPTL) is diagnosed, managed and treated internationally. The development of clinical guidelines requires an evidence-based approach to improve outcome and allow more efficient use of resources. With recent advances in our understanding of the etiology and mechanisms of SPTL and the availability of safer, more specific tocolytics, it was felt that guidelines should be developed to achieve, if possible, an European consensus in patient diagnosis, management and treatment.

The interval to spontaneous delivery following discontinuation of maintenance tocolysis

OBJECTIVE

To determine the interval to spontaneous delivery following discontinuation of continuous subcutaneous terbutaline (SQT).

METHODS

Singleton and twin gestations receiving outpatient preterm labor management services with SQT were identified from a database. Patients having SQT discontinued at 33.0-35.9 weeks (in a stable condition, not hospitalized and with known cervical status at discontinuation) with subsequent spontaneous labor and delivery were included (n = 1420). Data were compared by gestation type, week of SQT discontinuation and cervical dilatation using Kruskal-Wallis and Fisher's exact test analyses (p < 0.05 statistically significant).

RESULTS

Spontaneous preterm delivery occurred in 63.0% of singletons and 87.9% of twins. Although stable at SQT discontinuation, 32.5% of singletons and 59.9% of twins delivered within three days. The interval from discontinuation of SQT to delivery was less for twin than singleton gestations (5.1 +/- 6.5 vs. 11.0 +/- 10.5 days, respectively, p < 0.001). CONCLUSIONS. Preterm discontinuation of SQT should be avoided if additional pregnancy prolongation is desired.

Tocolysis in women with preterm labor between 32 0/7 and 34 6/7 weeks of gestation: a randomized controlled pilot study

OBJECTIVE

The purpose of this study was to determine whether intravenous magnesium sulfate (MgSO4) followed by oral nifidepine tocolysis in women with preterm labor between 32 0/7 and 34 6/7 weeks' gestation reduces neonatal hospital stay.

STUDY DESIGN

Fifty-four women between 32 0/7 and 34 6/7 weeks with preterm labor were randomized to receive either MgSO4 and oral nifidepine (n = 24) or no tocolysis (n = 30). All women received betamethasone and prophylactic antibiotics. The primary outcome was total neonatal hospital stay. Data were analyzed using Chi-square and Mann Whitney U test.

RESULTS

The 2 groups had similar mean cervical dilation and gestational age at enrollment. There were no statistically significant differences in total neonatal hospital stay (5.8 +/- 7.2 days; median of 3 days in the no tocolysis vs. 7.5 +/- 8.6 days; median of 3 days in the tocolysis group), rate of preterm delivery (57% vs. 75%) or need for oxygen supplementation (7% vs. 21%, p < 0.23). The neonatal complications were similar in each group.

CONCLUSION

Tocolysis after 32 weeks gestation does not reduce neonatal hospital stay.

The Evaluation of the Fetal Fibronectin Test for Prediction of Preterm Delivery in Symptomatic Patients

OBJECTIVE

This study was conducted to evaluate the usefulness of testing for fetal fibronectin (fFN) to rule out the diagnosis of preterm labour in symptomatic patients in a Canadian setting.

METHODS

This was a prospective, blinded clinical evaluation of fFN testing in women presenting with threatened preterm labour at between 24 and 34 weeks' gestation at two Canadian tertiary care centres.

RESULTS

Of the 149 women tested, 32 had a positive fFN test. In the total patient population, 10.1% delivered within seven days of testing, and 18.2% delivered prior to 34 weeks. A negative fFN result was associated with a 97.4% likelihood of delivering more than seven days after testing and with a 91.4% chance of delivering after 34 weeks.

CONCLUSION

The fFN test appears to provide useful information in the risk assessment of Canadian women presenting with symptoms compatible with preterm labour. A negative test has a high predictive value for delivering more than seven days after presentation.

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 STRATEGY

We searched the Cochrane Pregnancy and Childbirth Trials Register (June 2005) and MEDLINE (from 1966 to August 2003).

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

Eleven randomised controlled trials (RCTs) were included. No differences were seen for admission to the neonatal intensive care unit when betamimetics were compared with placebo (relative risk (RR) 1.29, 95% confidence interval (CI) 0.64 to 2.60; one RCT of terbutaline with 140 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 four RCTs, two comparing ritodrine with placebo/no treatment and two comparing terbutaline with placebo/no treatment (RR 1.08, 95% CI 0.88 to 1.32, 384 women). No differences between betamimetics and placebo, no treatment or other tocolytics were seen 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.

Nifedipine versus ritodrine for suppression of preterm labor. Comparison of their efficacy and secondary effects

OBJECTIVES

To compare the efficacy of nifedipine and ritodrine in prolonging pregnancy beyond 48 h, 1 week and 36.0 weeks and to evaluate maternal side effects and adverse perinatal outcome.

STUDY DESIGN

Non-blinded, randomized controlled trial. Eighty patients with singleton pregnancies admitted for preterm labor with intact membranes between 22 and 35 weeks of gestation were included in the study. Preterm labor was defined as the persistence of at least two symptomatic uterine contractions within a 10 min period during 60 min after admission and despite bed rest.

RESULTS

Forty women received oral nifedipine and forty intravenous ritodrine. Two patients, one from each group, were excluded because of loss to follow-up after discharge. Therefore, 39 women in the nifedipine and the ritodrine groups, respectively, were evaluable for the final analysis. Baseline characteristics were comparable in both groups. The percentage of initial response, the speed of onset of action and the rate of successful treatment within 48 h were significantly better in the ritodrine group. However, prolongation of pregnancy beyond 7 days and 36 weeks of pregnancy was similar with a significantly lower rate of side effects in the nifedipine group.

CONCLUSIONS

In this small trial, ritodrine provided more effective tocolysis within the first 48 h than nifedipine at the doses used in this study, although with a significantly higher rate of side effects.

beta-Agonist tocolytic therapy

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

Oxytocin receptor antagonists for inhibiting preterm labour

BACKGROUND

Preterm birth, defined as birth before 37 completed weeks, is the single most important cause of perinatal mortality and morbidity in high-income countries. Oxytocin receptor antagonists have been proposed as effective tocolytic agents for women in preterm labour to postpone the birth, with fewer side-effects than other tocolytic agents.

OBJECTIVES

To assess the effects on maternal, fetal and neonatal outcomes of tocolysis with oxytocin receptor antagonists for women with preterm labour compared with placebo or no intervention and compared with any other tocolytic agent.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (September 2004), CENTRAL (The Cochrane Library, Issue 3, 2004), MEDLINE (1965 to June 2004), EMBASE (1988 to June 2004).

SELECTION CRITERIA

Randomised trials of oxytocin receptor antagonists for tocolysis in the management of women in labour between 20 and 36 weeks' gestation.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated methodological quality and extracted trial data. We sought additional information from trial authors.

MAIN RESULTS

Six trials (1695 women) were included. Compared with placebo, atosiban did not reduce incidence of preterm birth or improve neonatal outcome. In one trial (583 infants), atosiban was associated with an increase in infant deaths at 12 months of age compared with placebo (relative risk (RR) 6.15; 95% confidence intervals (CI) 1.39 to 27.22). However, this trial randomised significantly more women to atosiban before 26 weeks' gestation. Use of atosiban resulted in lower infant birthweight (weighted mean difference -138.31 gm; 95% CI -248.76 to -27.86) and more maternal adverse drug reactions (RR 4.02; 95% CI 2.05 to 7.85, 2 trials, 613 women).Compared with betamimetics, atosiban increased the numbers of infants born under 1500 gm (RR 1.96; 95% CI 1.15 to 3.35, 2 trials, 575 infants). Atosiban was associated with fewer maternal drug reactions requiring treatment cessation (RR 0.04; 95% CI 0.02 to 0.11, number needed to treat 6; 95% CI 5 to 7, 4 trials, 1035 women).

AUTHORS' CONCLUSIONS

This review failed to demonstrate the superiority of atosiban over betamimetics or placebo in terms of tocolytic efficacy or infant outcomes. The finding of an increase in infant deaths in one placebo controlled trial warrants caution. A recent Cochrane review suggests that calcium channel blockers (mainly nifedipine) are associated with better neonatal outcome and fewer maternal side-effects than betamimetics. However, a randomised comparison of nifedipine with placebo is not available. Further well-designed randomised controlled trials of tocolytic therapy are needed. Such trials should incorporate a placebo arm.

Cyclo-oxygenase (COX) inhibitors for treating preterm labour

BACKGROUND

Preterm birth is a major cause of perinatal mortality and morbidity. Cyclo-oxygenase (COX) inhibitors inhibit uterine contractions, are easily administered and have fewer maternal side-effects compared to conventional tocolytics. However, adverse effects have been reported on the fetus and newborn as a result of exposure to COX inhibitors.

OBJECTIVES

To assess the effects on maternal, fetal and neonatal outcomes of COX inhibitors administered as a tocolytic agent to women in preterm labour when compared with (i) placebo or no intervention and (ii) other tocolytics. In addition, to compare the effects of non-selective COX inhibitors with COX-2 selective inhibitors.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's trials register (August 2004). We also contacted recognised experts and cross referenced relevant material.

SELECTION CRITERIA

All published and unpublished randomised trials in which COX inhibitors were used for tocolysis for women in labour between 20 and 36 completed weeks' gestation.

DATA COLLECTION AND ANALYSIS

Three authors independently evaluated methodological quality and extracted data. We sought additional information from trial authors.

MAIN RESULTS

This review includes outcome data from 13 trials with a total of 713 women. The non-selective COX inhibitor, indomethacin was used in 10 trials. When compared with placebo, COX inhibition (indomethacin only) resulted in a reduction in birth before 37 weeks' gestation (relative risk (RR) 0.21; one trial, 36 women), an increase in gestational age (weighted mean difference (WMD) 3.53 weeks) and birthweight (WMD 716.34 gm; two trials, 67 women). Compared to any other tocolytic, COX inhibition resulted in a reduction in birth before 37 weeks' gestation (RR 0.53; three trials, 168 women) and a reduction in maternal drug reaction requiring cessation of treatment (RR 0.07; five trials and 355 women). A comparison of non-selective COX inhibitors versus any COX-2 inhibitor (two trials, 54 women) did not demonstrate any differences in maternal or neonatal outcomes. Due to small numbers, all estimates of effect are imprecise and need to be interpreted with caution. Potential adverse effects of COX inhibition on the fetus, newborn or mother could not be adequately assessed due to insufficient data.

AUTHORS' CONCLUSIONS

There is insufficient information on which to base decisions about the role of COX inhibition for women in preterm labour. Further well designed trials are needed.

Maintenance tocolysis

BACKGROUND

Women who are undelivered after 48 hours of tocolysis remain at increased risk of preterm labour, but it is not clear whether prolonged treatment is effective.

OBJECTIVE

To review the current evidence for the effectiveness of maintenance tocolysis.

METHODS

The results of published systematic reviews were summarised.

RESULTS

Four systematic reviews and two trials published too recently for inclusion were identified. Maintenance tocolysis with beta-agonists and magnesium sulphate was ineffective in prolonging gestation or reducing any adverse fetal outcomes. One trial of maintenance tocolysis with nifedipine was underpowered to rule out an effect on prolonging gestation. One trial using the oxytocin receptor blocker, atosiban, showed that this drug used as maintenance tocolysis does prolong gestation, but the trial was too small to demonstrate any reduction in substantive fetal outcomes.

CONCLUSIONS

There is insufficient evidence to justify the routine use of maintenance tocolysis in preterm labour. It remains plausible that prolongation of gestation might be beneficial in selected cases of very preterm labour where fetal compromise and infection have been ruled out. The only tocolytic that has been shown to prolong gestation when used as maintenance therapy is atosiban.

Preventing Preterm Birth: What Works, What Doesn???t

Preterm birth is one of the most important problems in medicine today with an alarming frequency and economic impact. This paper reviews recent research findings specifically addressing the following primary and secondary prevention interventions: cerclage placement, detection and treatment of infections, progesterone administration, antibiotics in preterm labor and the use of tocolysis. The effectiveness of these interventions is presented in terms of the number needed to treat and number needed to harm. At the present, most of our interventions fail to demonstrate benefit in terms of prevention of preterm birth and improvement of neonatal outcomes. Use of progesterone may hold promise, but whether we will develop effective interventions to reduce risks for all women remains to be seen.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to summarize the epidemiology of preterm births in the U.S., to outline the primary preventive measures for preterm birth, and to interpret the relative effectiveness of the various preventive measures.

Oral nifedipine maintenance therapy after acute intravenous tocolysis in preterm labor

AIMS

Our aim was to evaluate the efficacy of maintenance oral nifedipine in pregnant women initially treated with intravenous ritodrine plus verapamil for preterm labor.

METHODS

The study included 73 patients with preterm labor with intact membranes. Patients were randomized to receive either maintenance oral nifedipine therapy (n=37) administered 20 mg every six hours or no treatment (controls, n=36) after discontinuation of acute intravenous tocolysis.

RESULTS

Compared to the control group, the mean +/- SD time gained from initiation of maintenance therapy to delivery (26.65 +/- 18.89 vs. 16.14 +/- 12.91 days, p=0.007) and the gestational age at delivery (37.03 +/- 2.06 vs. 35.1 +/- 3 weeks, p=0.003) were higher in the nifedipine maintenance therapy group. The proportion of patients who required one or more courses of subsequent intravenous therapy and perinatal outcomes were similar in the maintenance therapy and control groups.

CONCLUSIONS

The gestational age and time gained from initiation of maintenance therapy to delivery were longer in women receiving oral maintenance tocolysis with nifedipine. However, maintenance therapy did not decrease the recurrence of preterm labor episodes or improve perinatal outcomes.

Management options for preterm labour in Canada

OBJECTIVES

(1) To determine the current use of treatment options for preterm labour and (2) to review the relative safety and efficacy of each class of tocolytic agent.

METHODS

MEDLINE and the Cochrane Library were searched using the terms "preterm delivery," "preterm labour," and "tocolysis" alone, and in combination with the terms "betamimetics," "ritodrine," "magnesium sulfate," "calcium channel blockers," "nifedipine," "prostaglandin synthetase inhibitors," "indomethacin," "glyceryl trinitrate," "nitroglycerin," "oxytocin antagonists," and "atosiban." Randomized controlled trials (RCTs) that compared the effect of a tocolytic with a placebo or other tocolytic in women with preterm labour were selected. Trials were assessed according to Jadad's validated quality scale for assessing the quality of RCTs. Thirty two RCTs retrieved met the inclusion criteria. Information not evident from RCTs was sought from non-randomized clinical trials, cohort studies, case control studies, case series, and case reports. Data from the Canadian Survey on Tocolytic Use was obtained directly from the Society of Obstetricians and Gynaecologists of Canada (SOGC).

RESULTS

The available evidence on the use of tocolytics to prolong pregnancy fails to show benefits in neonatal survival and reduced disability. This uncertainty of benefit makes the issue of fetal and maternal drug toxicity more important. There is great concern among SOGC members over the lack of effective and safe treatment options for the management of preterm labour.

CONCLUSIONS

Further well-designed placebo-controlled trials are necessary to study the efficacy and safety of tocolytics in managing preterm labour.

Pregnancy and economic outcomes in patients treated for recurrent preterm labor

OBJECTIVE

To compare clinical and cost-effectiveness of treating recurrent preterm labor (RPTL) with oral nifedipine versus continuous subcutaneous terbutaline infusion (SQT).

STUDY DESIGN

Women with singleton gestations prescribed nifedipine for tocolysis following first diagnosis of preterm labor were identified. Women hospitalized with RPTL at <34 weeks were matched by gestational age (GA) after resuming nifedipine (NIF group) with women prescribed SQT (SQT group) after stabilization. Healthcare utilization costs were modeled and compared.

RESULTS

This study analyzed 142 matched pairs. GA at RPTL (matched variable) was 30.4+/-2.6 weeks. GA at delivery was earlier in the NIF group versus the SQT group (35.7+/-3.1 weeks versus 36.6+/-2.1 weeks, p=0.004). Overall, infants from the NIF group had lower birth weights and higher nursery days than infants from the SQT group. Healthcare utilization costs were greater in the NIF group versus the SQT group (37,040+/-47,518 US dollars versus 26,546+/-25,386 US dollars, p=0.014).

CONCLUSION

Treating RPTL with SQT versus oral nifedipine resulted in a later GA at delivery, improved neonatal outcome, and increased cost-effectiveness.

Maintenance therapy with calcium channel blockers for preventing preterm birth after threatened preterm labour

BACKGROUND

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

OBJECTIVES

To assess the effects of calcium channel blockers as maintenance therapy on preventing preterm birth after threatened preterm labour.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (31 March 2004); MEDLINE (1966 to March 2004) and DARE (June 2003).

SELECTION CRITERIA

Randomised controlled trials of calcium channel blockers used as maintenance therapy to prevent preterm birth after threatened preterm labour, compared with alternative drug therapy, placebo or no treatment.

DATA COLLECTION AND ANALYSIS

Two reviewers independently applied the selection criteria, extracted data from the included study and assessed study quality.

MAIN RESULTS

One trial of 74 women was included. No difference in the incidence of preterm birth was found when calcium channel blocker (nifedipine) maintenance therapy was compared with no treatment. Twenty-five women out of 37 in each group gave birth before 37 weeks (relative risk 1.00, 95% confidence interval 0.73 to 1.37). The trial did not report stillbirths and neonatal deaths prior to discharge. Neurological follow up of the infants was not addressed.

REVIEWERS' CONCLUSIONS

The role of maintenance therapy with calcium channel blockers for preventing preterm birth is not clear. Well designed randomised trials of sufficient size with relevant outcomes are required.

The therapeutic value of maintenance tocolysis: an overview of the evidence

The results obtained from current systematic overview do not support the routine administration of maintenance tocolytic treatment after parenteral tocolytic therapy has halted acute preterm labor. Eliminating or reducing such routine maintenance therapy, therefore, could substantially decrease costs and side effects associated with managing preterm labor without compromising perinatal outcomes. It remains to be elucidated whether it will become possible to accurately identify some groups of pregnancies for which maintenance tocolysis would be beneficial.

Continuous subcutaneous terbutaline administration prolongs pregnancy after recurrent preterm labor

OBJECTIVE

This study was undertaken to study the effectiveness of continuous subcutaneous terbutaline (SQT) in the home after recurrent preterm labor (RPTL).

STUDY DESIGN

Women with RPTL at less than 32 weeks' gestation were treated with continuous SQT administered in the home compared with matched control patients.

RESULTS

Fifteen SQT patients were compared with 45 women (3:1) treated with no tocolytic therapy after hospitalization. Gestational age at delivery more than 37 weeks (53% vs 4%), percentage delivered at less than 32 weeks (0% vs 47%), overall and pregnancy prolongation (49.8 +/- 19.2 days vs 24.5 +/- 12.8 days) were all significantly better in the study group (P <.001). The total number of maternal hospital days (9.8 +/- 2.1 vs 15.9 +/- 7.4, P <.0001), duration of NICU stay (1.9 +/- 4.9 vs 19.8 +/- 29.3 days, P <.001), and total cost for newborn care (6,995 +/- 14,822 US dollars vs 62,033 +/- 89,978 US dollars, P <.002) favored the study patients. For every dollar spent on SQT, there was a savings of 4.67 US dollars in newborn hospital costs for control patients.

CONCLUSION

In this small study, the use of SQT significantly prolongs pregnancy, decreases serious neonatal complications, and reduces the duration of hospitalization for both mother and infant, as well as neonatal costs.

Does preterm cervical dilatation imply imminent labor in multifetal pregnancies?

OBJECTIVE

Women with multifetal pregnancies are at increased risk of preterm labor and delivery compared with singleton pregnancies. Presentation with advanced cervical dilatation of 3-4 cm is generally regarded as being in the midst of the first stage of labor. The purpose of this report is to present our experience in cases of advanced cervical dilatation and arrested preterm labor in multifetal pregnancies.

METHODS

This study is a retrospective analysis of threatened preterm deliveries in women with multifetal pregnancies. Fifteen cases with advanced cervical dilatation that remained undelivered for at least 10 days are presented and reviewed.

RESULTS

Out of 1219 women presenting with multifetal pregnancies to the high-risk maternity unit, 15 women who presented with advanced cervical dilatation of 3-5 cm and remained undelivered for at least 10 days were identified. Eight women presented with twins and seven with triplets. The mean latency period to delivery was 21.7 days (range 10-43 days). The mean gestational age at diagnosis was 31.3 weeks (range 26.3-35.3 weeks). The mean gestational age at delivery was 34.5 weeks (range 29.5-38.0 weeks). Twelve women delivered vaginally in this group, giving a cesarean section rate of 20%.

CONCLUSIONS

In the women presented in this series advanced cervical dilatation did not lead directly to preterm labor and delivery, we believe due to their having a multifetal gestation. It is possible that dilatation of the cervix in these cases is not a result of preterm labor but rather a relative cervical incompetence resulting from overdistention of the uterus in twins or higher-order gestations. This phenomenon may be underdiagnosed because of a tendency to forego frequent digital examinations remote from term without a clear indication. More information is therefore needed on the mechanism of cervical change during multifetal pregnancy.

Are developing beta-adrenoceptors able to desensitize? Acute and chronic effects of beta-agonists in neonatal heart and liver

During fetal and neonatal development, beta-adrenergic receptors (beta-ARs) appear to be resistant to desensitization by beta-agonist drugs. To determine the mechanisms underlying the regulatory differences between adults and neonates, we administered isoproterenol, a mixed beta(1)/beta(2)-AR agonist, and terbutaline, a beta(2)-selective agonist. Effects were examined in the ensuing 4 h after a single injection, or after the last of four daily injections. We prepared cell membranes from heart (predominantly beta(1)-ARs) and liver (predominantly beta(2)-ARs) and assessed signal transduction in the adenylyl cyclase (AC) pathway. In the first few hours after a single administration of isoproterenol to adult rats, cardiac beta-ARs showed activation of G proteins (elevated AC response to forskolin) and desensitization of beta-AR-mediated responses; after the fourth injection, heterologous desensitization emerged, characterized by a loss of signaling mediated either through beta-ARs or glucagon receptors. Terbutaline evoked an increase in the forskolin response but no desensitization of receptor-mediated responses. When we gave the same treatments to neonatal rats, we observed cardiac G protein activation, but there was neither homologous nor heterologous desensitization of beta-ARs or glucagon receptors. In the adult liver, isoproterenol and terbutaline both failed to evoke desensitization, regardless of whether the drugs were given once or for 4 days. In neonates, however, acute or chronic treatment elicited homologous desensitization of beta-AR-mediated AC signaling, while sensitizing the response to glucagon. These results show that neonatal beta-ARs are inherently capable of desensitization in some, but not all, cell types; cellular responses can be maintained through heterologous sensitization of signaling proteins downstream from the receptor. Differences from adult patterns of response are highly tissue selective and are likely to depend on ontogenetic differences in subtypes of beta-ARs and AC.

Treatment of preterm labor

The ultimate goal of treating preterm labor is to prolong the pregnancy long enough to decrease the incidence of neonatal mortality and morbidity associated with prematurity, while minimizing maternal and fetal risks. There are many controversies in treating preterm labor. Much of this controversy stems from the difficulty in establishing efficacy and safety of interventions and uncertainty of the diagnosis of preterm labor. This article outlines conventional measures and tocolytic therapy directed at prolonging the pregnancy. A review of the effect of tocolytic agents, administration, side effects, and nursing interventions is included. Key words: preterm labor treatment,

beta-Adrenergic modulation of muscarinic cholinergic receptor expression and function in developing heart

Imbalances of beta-adrenoceptor (beta-AR) and muscarinic ACh receptor (mAChR) input are thought to underlie perinatal cardiovascular abnormalities in conditions such as sudden infant death syndrome. Administration of isoproterenol, a beta(1)/beta(2)-AR agonist, to neonatal rats on postnatal days (PN) 2-5 caused downregulation of cardiac m(2)AChRs and a corresponding decrement in their control of adenylyl cyclase activity. Terbutaline, a beta(2)-selective agonist that crosses the placenta and the blood-brain barrier, was also effective when given either on PN 2-5 or during gestational days 17-20. Terbutaline failed to downregulate brain m(2)AChRs, even though it downregulated beta-ARs; beta-ARs and m(2)AChRs are located on different cell populations in the brain, but they are on the same cells in the heart. Destruction of catecholaminergic neurons with neonatal 6-hydroxydopamine upregulated cardiac but not brain m(2)AChRs. These results suggest that perinatal beta-AR stimulation shifts cardiac receptor production away from the generation of m(2)AChRs so that the development of sympathetic innervation acts as a negative modulator of cholinergic function. Accordingly, tocolytic therapy with beta-AR agonists may compromise the perinatal balance of adrenergic and cholinergic inputs.

Terbutaline pump maintenance therapy after threatened preterm labor for preventing preterm birth

BACKGROUND

Women with preterm labor that is arrested with tocolytic therapy are at increased risk of recurrent preterm labor. Terbutaline pump maintenance therapy has been given to such women to decrease the risk of recurrent preterm labor, preterm birth, and its consequences.

OBJECTIVES

To determine the effectiveness and safety of terbutaline pump maintenance therapy after threatened preterm labor in preventing preterm birth and its complications.

SEARCH STRATEGY

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

SELECTION CRITERIA

Randomized trials comparing terbutaline pump maintenance therapy with alternative therapy, placebo, or no therapy after threatened preterm labor.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the studies for inclusion and then extracted data from eligible studies.

MAIN RESULTS

We included two studies. Terbutaline pump maintenance therapy did not appear to offer any advantages over the saline placebo pump or oral terbutaline maintenance therapy in preventing preterm births by prolonging pregnancy or its complications among women with arrested preterm labor. The weighted mean difference (WMD) for gestational age at birth was -0.1 weeks (95% confidence interval (CI) -1.7 to 1.4) for terbutaline pump therapy compared with saline placebo pump for both trials combined and 1.4 weeks (95% CI -1.1 to 3.9) for terbutaline pump versus oral terbutaline therapy for the first trial. The second trial reported a relative risk (RR) of 1.17 (95% CI 0.79 to 1.73) of preterm birth (less than 37 completed weeks) and a RR of 0.97 (95% CI 0.51 to 1.84) of very preterm birth (less than 34 completed weeks) for terbutaline pump compared with saline placebo pump. Terbutaline pump therapy also did not result in a higher rate of therapy continuation or a lower rate of infant complications. No data were reported on long-term infant outcomes, costs, or maternal assessment of therapy.

REVIEWER'S CONCLUSIONS

Terbutaline pump maintenance therapy has not been shown to decrease the risk of preterm birth by prolonging pregnancy. Furthermore, the lack of information on the safety of the therapy, as well as its substantial expense, argues against its role in the management of arrested preterm labor. Future use should only be in the context of well-conducted, adequately powered randomized controlled trials.