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 β-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.     

Effectiveness of nifedipine versus atosiban for tocolysis in preterm labour: a meta-analysis with an indirect comparison of randomised trials

Objective To explore the effectiveness of nifedipine compared with atosiban for tocolysis in preterm labour.
Design A systematic review of randomised controlled trials with meta-analysis using adjusted indirect comparison.
Population Six hundred and seventy-nine women recruited in nine randomised trials evaluating the effectiveness of nifedipine versus β-agonists, and 852 women recruited in four trials of atosiban versus β-agonists. There were no trials comparing nifedipine directly with atosiban.
Methods We performed meta-analysis with a technique involving an adjusted indirect comparison between nifedipine and atosiban using β-agonists as the common comparator. This approach preserves the benefit accrued by randomisation in the original comparisons.
Main outcome measures Reduction in neonatal respiratory distress syndrome and delay in delivery by 48 hours.
Results Nifedipine tocolysis was associated with a significant reduction in respiratory distress syndrome compared with atosiban (OR 0.55, 95% CI 0.32–0.97). It also increased the number of women whose delivery was delayed by 48 hours (OR 1.20, 95% CI 0.73–1.95), although this result was not statistically significant.
Conclusions When indirectly compared with atosiban, nifedipine tocolysis is more effective. In the absence of a direct comparison, our analysis provides a way to explore the potential benefits of nifedipine versus atosiban.     

The quality of nifedipine studies used to assess tocolytic efficacy: a systematic review

OBJECTIVE: To assess the quality of studies of nifedipine used to treat spontaneous preterm labor. DESIGN: A systematic review of study quality using a novel validity assessment tool, examining method-specific and topic-specific items in the domains of selection, performance and measurement biases. DATA SOURCES: Medline (1996-2003), EMBASE (1996-2003), BIOSIS (1993-2003), Current Contents (1995-2003), DERWENT DRUGFILE (1983-2003), Cochrane Database of Systematic Reviews. Bibliographies of existing meta-analyses and systematic reviews of nifedipine as a tocolytic. METHODS OF STUDY SELECTION: Forty-five studies evaluating the effectiveness of nifedipine were identified. DATA EXTRACTION: Each study was assessed for 40 method-specific and topic-specific items of quality in duplicate using piloted data extraction forms. Disagreements between assessors were settled by consensus/arbitration. DATA SYNTHESIS: Very few of the studies complied with adequacy criteria of quality for either method-specific or topic-specific items. There was no improvement in quality over time. The quality of method-specific items was significantly poorer when compared with topic-specific items of quality overall (P<0.0001) and in the domains of selection bias (P<0.0001) and performance bias (P<0.0001). CONCLUSION: Studies of the effectiveness of nifedipine as a tocolytic are of poorer quality with respect to method-specific items than topic-specific items. These deficiencies should be highlighted in meta-analyses or systematic reviews which measure efficacy and should influence the generation of guideline statements or recommendations for the use of nifedipine as a tocolytic. A large randomized trial fulfilling the quality items is necessary to assess the real efficacy of nifedipine in preterm labor.     

Adverse effects of tocolytic therapy

The rationale for using tocolytics in preterm labour is to enable transfer of the mother to a tertiary centre and to prolong pregnancy sufficiently so that glucocorticoids can be administered to the mother. There is little question that these short term objectives can be achieved with contemporary tocolytics. Whether tocolytics can maintain pregnancy for sufficient periods to enable in utero maturation to occur remains an unresolved question. When a decision is made to use tocolytics, the clinician is faced with a multitude of choices with side effects, efficacy and ease of administration generally being the most important considerations. Placebo-controlled studies suggest that the β-agonists, prostaglandin inhibitors and atosiban are effective in prolonging pregnancy for 24–48 hours. Of these three agents, atosiban has the best safety profile. There are no placebo-controlled studies with calcium channel blockers or nitric oxide donors. However, because of their ease of use and efficacy compared with the β-agonists, calcium channel blockers are widely used. Calcium channel blockers appear to have a better safety profile than the β-agonists, but there are still significant cardiovascular side effects associated with their use. Indomethacin, although proven to be efficacious, has a safety profile that limits its utility for other than short courses. Magnesium sulphate is the most commonly used tocolytic in the United States, despite a lack of evidence for its efficacy. Although magnesium sulphate appears to have a good safety profile, serious side effects have been reported with its use. The choice of tocolytics is commonly based on personal preference. Whichever tocolytic is chosen, the fundamental parturitional process is not reversed by contemporary treatment, rather a reduction in uterine response to a stimulant; thus, the expectations of tocolytic treatment need to be reconsidered.     

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.     

Emerging tocolytics for maintenance therapy of preterm labour: oxytocin antagonists and calcium channel blockers

The incidence of spontaneous preterm labour and preterm birth has increased, and its management worldwide remains suboptimal. While considerable debate remains as to whether long-term maintenance tocolysis is appropriate after an episode of spontaneous preterm labour, many practitioners support its use. Several drugs have been used for maintenance tocolysis, but they differ in terms of safety and efficacy. Atosiban and nifedipine are preferable for maintenance tocolysis, as they have been shown to be as effective as ritodrine while being associated with fewer adverse effects. Nifedipine is not licensed for use as a tocolytic. An ideal tocolytic should be utero specific, with few fetomaternal and fetal adverse effects, and should significantly improve perinatal outcome. To warrant the use of maintenance therapy, larger trials in women at particular gestational age ranges may be needed, in which the primary endpoints are perinatal outcomes. The inclusion of cost-effectiveness analyses would also be of benefit.     

Calcium channel blockers in the management of preterm labor and hypertension in pregnancy.

Calcium channel blockers (CCBs) have the ability to inhibit contractility in smooth muscle cells. CCBs have an already established role in the treatment of non-pregnant hypertension and angina pectoris. Some epidemiological studies found an association between the use of CCBs and an increase in cardiovascular mortality, malignancy, and gastrointestinal bleeding. More recent studies with many more patients and a longer follow-up did not find these associations. In obstetrics CCBs have become increasingly popular for the management of preterm labor and pregnancy-induced hypertensive disorders. Meta-analysis shows that use of nifedipine in comparison with betamimetics is associated with a more frequent successful prolongation of pregnancy in case of preterm labor, resulting in significantly fewer admissions of newborns to the neonatal intensive care unit (NICU), and is associated with a lower incidence of respiratory distress syndrome. No adverse fetal side effects in humans have been reported with the use of nifedipine for obstetric indications. Nifedipine is an effective and safe drug to use when tocolytic therapy is indicated for preterm labor. In preeclampsia nifedipine effectively lowers blood pressure and can be a good alternative for (di) hydralazine.     

Tocolysis and preterm labour

PURPOSE OF REVIEW: There is persisting controversy about tocolytic treatment for preterm labour. This review addresses this controversy by appraising the recent clinical literature. RECENT FINDINGS: Surveys of obstetricians indicate a high usage of tocolysis for preterm labour, but evidence that this treatment confers overall benefit is still lacking. Betamimetics are now, correctly, being abandoned in favour of nifedipine, which has superior tocolytic properties and better neonatal outcomes. There is no evidence of effectiveness for magnesium sulphate as a tocolytic. Atosiban is a newer agent, which appears to be effective in delaying preterm birth with a favourable maternal safety profile, but there are persisting concerns about the lack of impact on perinatal mortality and morbidity. Current research is addressing the COX-2 inhibitor, rofecoxib, which has theoretical advantages with respect to fetal safety. SUMMARY: For the relatively small proportion of women in otherwise uncomplicated preterm labour prior to 34 weeks' gestation, there appears to be a place for short-term tocolysis to gain time so that corticosteroids can be administered to enhance fetal lung maturation and, if necessary, to transfer the woman to a facility with a neonatal intensive care unit. Nifedipine is an effective and cheap tocolytic agent. Atosiban appears to also be effective, but it is expensive and not universally available. Betamimetics and magnesium sulphate should be abandoned as tocolytic agents. There is a need for further clinical trials to establish an unequivocal evidence base for tocolysis, which requires placebo-controlled trials, and for comparative trials to identify the agent with superior characteristics.     

The effects of the tocolytics atosiban and nifedipine on fetal movements,heart rate and blood flow

Background. The choice of first-line tocolytic agent is a topic of worldwide debate. The oxytocin receptor antagonist atosiban and the calcium antagonist nifedipine appear to be effective in postponing delivery. However, information is lacking on their possible effects on the fetal biophysical profile.

Objective. To study the direct fetal effects of tocolysis with atosiban or nifedipine combined with a course of betamethasone.

Method. We performed a randomised controlled study including women with preterm labour requiring tocolytic treatment. Primary outcome measures were the effects on fetal heart rate (FHR) and its variation. Secondary endpoints were the effects on fetal movement and blood flow (pulsatility index – PI) of the umbilical (UA) and medial cerebral arteries (MCA).

Results. One-hour recordings of FHR and fetal movements were made on each of five successive days (days 0–4). Fetal blood flow velocity patterns were studied daily by Doppler ultrasound. Baseline characteristics of 31 women who had not delivered at day 0 and needed no escape tocolysis did not differ between the study groups. Multilevel analysis showed no significant effect of either tocolytic on FHR and movement parameters over the 5-day study period. The use of tocolytics also did not significantly alter the time courses of PI-values for UA (p = 0.37) and MCA (p = 0.62).

Conclusion. This study demonstrates for the first time the direct effects of atosiban on fetal movement, heart rate and blood flow. Tocolysis with either atosiban or nifedipine combined with betamethasone administration appears to have no direct fetal adverse effects.     

Use of tocolytics: what is the benefit of gaining 48 hours for the fetus?

Preterm birth remains one of the serious problems in perinatal medicine and is associated with an increased risk of neonatal complications and long-term morbidity. Although each day that delivery is delayed between 22 and 28 weeks of gestation increases survival by 3%, since most spontaneous preterm labour occurs between 28 and 34 weeks of gestation, this is of secondary concern; the primary goal of delay is to improve the function of certain systems in the fetus and to balance the risks of a hostile intrauterine environment with the complications of extrauterine preterm life. Although there is a lack of definitive evidence that tocolytic drugs improve outcome following spontaneous preterm labour and preterm birth, there is ample evidence that tocolysis delays delivery for long enough to permit administration of a complete course of antepartum glucocorticoids and to facilitate in utero transfer to a tertiary care unit where neonatal care will be optimal. Both these measures have been associated with improved outcomes; antepartum glucocorticoids reduce the incidence of respiratory distress syndrome, intraventricular haemorrhage, periventricular leucomalacia and necrotising enterocolitis, and in utero transfer is associated with decreased morbidity and mortality and less hospital-based intervention compared with postnatal transportation. Consequently, women who are more likely to benefit from tocolysis are those at early gestational ages, those needing transfer to a hospital that can provide neonatal intensive care and those who have not yet received a full course of antepartum glucocorticosteroids. In these cases, delaying labour for at least 48 hours with drugs such as atosiban should be considered, since it offers clear advantages for the fetus.     

Calcium channel blockers for tocolysis: a review of their role and safety following reports of serious adverse events

The use of nifedipine and other calcium channel blockers has become commonplace in the management of preterm labour. Several relatively small randomised trials have compared calcium channel blockers with beta-agonists and the meta-analyses of these studies have demonstrated superior or comparable efficacy and a superior adverse events profile. The safety of calcium channel blockers in pregnancy has not been rigorously evaluated and they remain unlicensed for use as tocolytics. Indeed, there is concern following a number of recent case studies that have reported serious adverse events after the administration of a calcium channel blocker as a tocolytic. In this article all these recently reported cases are critically reviewed and the pros and cons of tocolytic treatment options are discussed. Based on the findings of this review the following recommendations can be made with regard to tocolysis with calcium channel blockers: firstly, calcium channel blockers should not be combined with intravenous beta-agonists; secondly, intravenous nicardipine or high oral doses of nifedipine should not be used in cases where the mother is cardiovascular compromised or in cases of multiple gestation; finally, blood pressure should be monitored and cardiotocography recorded during the administration of immediate release tablets and patients should be advised to avoid chewing them. To truly establish the safety of tocolytics, all serious adverse effects of tocolytics should be reported to a central point and be critically reviewed.     

Clinical practice evaluation of atosiban in preterm labour management in six European countries

Objective  To evaluate the efficacy and safety of early administration compared with standard administration of atosiban, when predefined eligibility criteria were met.
Design  A prospective, open-label, randomised clinical trial. Women were randomised to receive atosiban either immediately (early) or when specified criteria, in terms of duration/frequency of uterine contraction or status of cervical dilation/effacement, were fulfilled (standard).
Setting  Carried out at 105 centres in six European countries.
Population  Pregnant women admitted to hospital in threatened preterm labour between 24 and 34 weeks of gestation, comprising a subgroup of women enrolled in the Tractocile Efficacy Assessment Survey in Europe (TREASURE) clinical experience review.
Main outcome measures  Efficacy was defined as the successful delay of delivery with no alternative tocolytic agent for 48 hours.
Results  More women in the early group remained undelivered at 48 hours with no alternative tocolytic agent compared with those who received atosiban when specified criteria were fulfilled (88.9 versus 76.1%; P = 0.03). Safety was comparable between the groups. There were no statistical differences in maternal, fetal or neonatal adverse events between the early and standard atosiban arms.
Conclusions  The use of atosiban was effective for the delay of preterm labour and presented no safety concerns irrespective of the time it was administered.     

Tocolysis with beta-adrenergic receptor agonists

Beta-adrenergic receptor agonists have been used for tocolysis in the setting of preterm labor for more than three decades. One of these agents, ritodrine hydrochloride, is the only Federal Drug Administration (FDA) approved drug for the treatment of preterm labor. Despite their widespread use, only a few prospective randomized placebo-controlled trials have been performed. These agents have been shown to have more patients deliver beyond 48 hours after the onset of treatment as compared with controls, but have never shown a difference in neonatal outcomes. Because they are one of the few tocolytic agents to have been shown to make a difference when compared with controls, the beta-agonists are commonly used as the control groups in studies examining the efficacy of newer tocolytic agents. In general, agents such as nifedipine, magnesium sulfate, and atosiban have not been shown to be more efficacious than the beta-agonists. However, several studies have shown these agents to have less side effects and lower discontinuation rates than the beta-agonists.     

Calcium channel blockers for inhibiting preterm labour; a systematic review of the evidence and a protocol for administration of nifedipine

OBJECTIVE: To assess the effects on maternal, fetal and neonatal outcomes of nifedipine (and other calcium channel blockers) administered as a tocolytic agent to women in preterm labour. METHODS: Standard methods of the Cochrane Collaboration and its Pregnancy and Childbirth Review Group were used. All published and unpublished randomised trials in which calcium channel blockers were used for tocolysis for women in preterm labour between 20 and 36 weeks' gestation, were considered. MAIN RESULTS: The systematic review includes 12 randomised controlled trials with a total of 1029 participating women. No trials were identified in which calcium channel blockers were compared with a placebo or no alternative tocolytic treatment. Calcium channel blockers appear to be more effective than betamimetic agents in prolonging pregnancy for 7 days or longer, are much less likely to cause maternal side-effects and are associated with reduced neonatal morbidity. CONCLUSION: Calcium channel blockers (especially nifedipine) can be considered safer and more effective tocolytic agents than betamimetics.     

Effectiveness and safety of the oxytocin antagonist atosiban versus beta-adrenergic agonists in the treatment of preterm labour

Objective To compare the effectiveness and safety of the oxytocin antagonist atosiban with conventional beta-adrenergic agonist (beta-agonist) therapy in the treatment of preterm labour.Design Three multinational, multicentre, double-blind, randomised, controlled trials.Setting Hospitals in Australia, Canada, Czech Republic, Denmark, France, Israel, Sweden, and the UK.Population Women diagnosed with preterm labour at 23–33 completed weeks of gestation.Methods Seven hundred and forty-two women were randomised; 733 received atosiban (n=363; intravenous (iv) bolus dose of 6.75 mg, then 300 μg/minute iv. for 3h and 100 μg/min iv thereafter) or beta-agonist (n=379; ritodrine, salbutamol or terbutaline iv; dose titrated) for at least 18h and up to 48 hours. Uterine contraction rate, cervical dilatation and effacement were used to assess progression of labour. An all patients treated analysis, using the Cochran-Mantel-Haenszel test, was performed.Main outcome measures Tocolytic effectiveness was assessed in terms of the number of women undelivered after 48 hours and seven days. Safety was assessed in terms of maternal side effects and neonatal morbidity.Results There were no significant differences between atosiban and β-agonists in delaying delivery for 48h (88.1% vs 88.9%; P=0.99) or seven days (79.7% versus 77.6%; P=0.28). Tocolytic effectiveness was also similar in terms of mean [SD] gestational age at delivery (35.8 [3.9] weeks vs 35.5 [4.1] weeks) and mean [SD] birthweight (2491 [813] g versus 2461 [831] g). Maternal side effects, particularly cardiovascular adverse events (8.3% vs 81.2%, P < 0.001), were reported more frequently in women given β-agonists, resulting in more treatment discontinuations due to side effects (1.1% vs 15.4%, P=0.0001). No statistical differences in neonatal/infant outcomes were observed with either study medication.Conclusions In the largest study of tocolytic therapy to date, atosiban was comparable in clinical effectiveness to conventional beta-agonist therapy, but was associated with fewer maternal cardiovascular side effects. We conclude that atosiban has clinical advantages over current tocolytic therapy.     

Multicentre, parallel group, randomised, single-blind study of the safety and efficacy of atosiban versus ritodrine in the treatment of acute preterm labour in Korean women

OBJECTIVE: To compare the efficacy and safety of atosiban with those of ritodrine in preterm labour. DESIGN: Multicentre, single-blind, randomised, controlled trial. SETTING: Obstetric units in six referral centres in Korea. POPULATION: Women with singleton pregnancies with preterm labour, between 24 and 33 + 6 weeks of gestation. METHODS: One hundred and twenty-eight women were randomised to receive intravenous atosiban (n= 63) or ritodrine (n= 65) and were stratified by gestational age (<28 weeks and >or=28 weeks). Atosiban or ritodrine was administered for up to 48 hours. Progression of labour was assessed by the frequency of contractions and cervical dilatation and effacement. Alternative tocolysis could be given as rescue therapy. MAIN OUTCOME MEASURE: Efficacy was assessed as the proportion of women in each group who did not deliver and did not need alternative tocolytic therapy at 48 hours and 7 days after therapy initiation. Safety was assessed as the numbers of maternal adverse events and neonatal morbidity. RESULTS: Tocolytic efficacy after 7 days was significantly better in the atosiban group than in the ritodrine group (60.3 versus 34.9%), but not at 48 hours (68.3 versus 58.7%). Maternal adverse events related to therapy were reported less frequently in the atosiban group (7.9 vs 70.8%; P= 0.0001), resulting in fewer early drug terminations due to adverse events (0 versus 20.0%; P= 0.0001). This, however, was not accompanied by a concurrent improvement in perinatal outcomes. CONCLUSION: The efficacy and safety of atosiban in the treatment of preterm labour were superior to those of ritodrine.     

Encuesta SEGO. Tratamiento de la amenaza de parto pretérmino en los hospitales españoles

Objective

To determine how threatened preterm labor is treated in Spanish hospitals.

Material and method

Under the aegis of the Spanish Society of Obstetrics and Gynecology, an Internet questionnaire on basic aspects of the treatment of threatened preterm labor was sent to 41 Spanish hospitals (37 public and four private hospitals).

Results

All hospitals use tocolysis in threatened preterm labor before 34th weeks. The most widely used tocolytic agent is atosiban (73,7%), followed by betamimetics (21.9%) and nifedipine (4.9%). Only 7.3% of the hospitals use tocolytics in threatened preterm labor after 34 weeks. All the hospitals use corticosteroids to accelerate lung maturation: 92.7% use betamethasone and 7.3% prefer dexamethasone. In 90% of the hospitals, steroid therapy is not repeated. In multiple pregnancies, the same steroid dose as that used in single pregnancies is administrated in all centers.

Conclusions

The most widely used tocolytic agent in Spanish hospitals is atosiban and the preferred corticosteroid is betamethasone.     

Significant delay of birth in advanced preterm labour at 23 gestational weeks with an oxytocin antagonist

CASE: A 27-year-old primigravid woman with advanced preterm labour at 23 weeks and 5 days gestation received tocolytic therapy with a continuous infusion of the oxytocin antagonist, atosiban, during 154 h. The delivery was postponed for 12 days. The baby was discharged after 3 months of neonatal care and at 6 months of age is healthy. The prolonged treatment was not associated with maternal or fetal side effects.     

Gentle obstetrical management for very early preterm deliveries

OBJECTIVE: In view of the general improvement in survival of very early preterm newborns the contribution of the obstetrical management to this development has been studied. METHODS: A comprehensive literature search was performed concentrating on prospective randomised clinical trials, meta-analyses and review articles dealing with different aspects of the obstetrical management of very early preterm deliveries which were published during the last 10 years. RESULTS: The benefit of antepartal administration of glucocorticoids to the mother for stimulation of pulmonary maturity of the fetus and the overall clinical condition of the preterm newborn at birth has been proven by several prospective randomised studies. In contrast, there is only indirect evidence for the benefit of an early transfer of these pregnancies to a perinatal centre. The benefit of a short-term prolongation of pregnancy by the administration of tocolytics is evident in the context of glucocorticoid administration for pulmonary maturity. There is no clear evidence for the benefit of long-term tocolytic treatment of preterm labour. Various prospective randomised trials comparing delivery by primary or elective caesarean section with vaginal birth combined with selective section as indicated by a deterioration of the condition of the fetus or the mother during the first or second stage of labour have clearly shown increased maternal morbidity in the elective caesarean section group. The expected advantage for the condition of the newborn could not be shown. In a meta-analysis of 6 such trials, the problem of recruiting participants was stressed. All 6 trials had to be terminated before the calculated number of study participants had been recruited. CONCLUSION: For planned early preterm delivery a transfer of the mother into perinatal centre is recommended for pregnancies beyond 22 0/7 weeks. Starting at 24 0/7 weeks, glucocorticoids should be administered. Between 24 0/7 and 24 6/7 weeks, survival chances remain clearly at less than 50%, and up to 50% of those surviving develop moderate to severe handicaps. Obstetrical management, in particular a decision for caesarean section due to fetal indication, must be individualised taking into account the wishes of the parents. Beyond 25 0/7 weeks, newborn survival should be given priority, and although clear evidence for the optimal mode of delivery is missing in cases of spontaneous labour leading to rapid dilatation of the cervix, with a normal singleton cephalic fetus, a vaginal delivery may be attempted. If under close supervision of labour there are signs of fetal or maternal deterioration, a caesarean section should be performed without delay. With breech presentation as well as twins or multiple fetuses there is a general trend towards primary caesarean section. In the absence of spontaneous labour and with an unripe cervix, elective caesarean section is considered as the method of choice for the delivery of the early preterm fetus.     

Effectiveness and safety of atosiban versus conventional treatment in the management of preterm labor

ObjectiveTo compare the efficacy of atosiban with conventional treatment of the threatened preterm labor.Materials and methodsAll the data of pregnant women with threatened preterm labor from January 1 to December 31, 2017, who received atosiban were collected. Pregnant women with conventional treatment (including β-agonists, indomethacin, magnesium sulphate and calcium channel blockers, alone or in combination) were used as control.ResultsThe proportion of women not requiring an alternative tocolytic treatment within 48 h and remaining undelivered was significantly higher in atosiban treatment group (89.3%; n = 25/28) compared with conventional treatment (24.2%; n = 8/33) (P < 0.0001). For therapy efficacy, there was also no significant difference between atosiban groups and conventional treatment groups in the low gestational ages. However, for the high gestational ages, atosiban treatment group showed higher efficacy (84%; n = 21/25 vs. 37.5%; n = 3/8) (P < 0.05). Moreover, a significantly higher proportion of women in the atosiban treated group (89.3%; n = 25/28) was observed compared with the conventional treatment groups (51.5%; n = 17/33) who did not receive an alternative tocolytic within 48 h (P < 0.01). Maternal and fetal safety was significantly superior with atosiban treatment.ConclusionsOur results support that atosiban would represent an advance over current tocolytic therapy especially for the high gestational ages.