A prospective randomized trial of acute tocolysis in term labour with atosiban or ritodrine

Acute tocolysis for intrapartum nonreassuring fetal status: how often does it prevent cesarean delivery? A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

This study aimed to evaluate the effectiveness of intrapartum acute tocolysis for nonreassuring fetal heart rate tracing in decreasing the incidence of cesarean delivery. Secondary outcomes included modes of delivery other than cesarean delivery, successful acute tocolysis, time-to-delivery interval, and short-term perinatal outcomes.

DATA SOURCES

Searches were performed in MEDLINE/PubMed, Embase, Scopus, the Cochrane Central Register of Controlled Trials and Reviews, ClinicalTrials.gov, and the International Clinical Trials Registry Platform from the inception of each database until February 2022.

STUDY ELIGIBILITY CRITERIA

Selection criteria included randomized controlled trials of laboring patients with singleton gestations randomized to receive intrapartum acute tocolysis for nonreassuring fetal heart rate tracing, as defined by the original trial.

METHODS

All analyses were done using an intention-to-treat approach, evaluating women according to the treatment group to which they were randomly allocated in the original trials. A frequentist network-meta-analysis was performed.

RESULTS

Four randomized clinical trials were eligible, including 605 patients with nonreassuring fetal heart rate tracing and singleton gestations at gestational ages >32 weeks. The cesarean delivery rate was similar among patients managed with different types of acute tocolysis. Acute tocolysis, compared with emergency delivery, was associated with improved neonatal acid-base status (notably decreasing the prevalence of base deficit >12 mmol/L [beta-2 agonists odds ratio, 0.61; 95% confidence interval, 0.37-0.99] and the rate of neonatal intensive care unit admission [beta-2 agonists odds ratio, 0.42; 95% confidence interval, 0.22-0.78]) and with an increase in the time-to-delivery interval (beta-2 agonists mean difference, 17.62 minutes; 95% confidence interval, 15.66-19.58); there was no reduction of cesarean delivery rate, showing an increased rate with atosiban and beta-2 agonists.

CONCLUSION

The cesarean delivery rate was not reduced by acute tocolysis when used for nonreassuring fetal heart rate tracing during labor. Acute tocolysis is associated with improved short-term fetal outcomes and safely increases the time-to-delivery interval.

Effects of acute tocolysis using ritodrine hydrochloride on foetal heart rate patterns in intrauterine foetal resuscitation: a retrospective, single-centre observational study

No consistent recommendations concerning the preferred tocolytic agents for intrauterine foetal resuscitation are available. We evaluated the effects of acute tocolysis (AT) using ritodrine hydrochloride on foetal heart rate (FHR) patterns and neonatal outcomes. We retrospectively analysed the data of patients undergoing emergency caesarean section because of non-reassuring foetal status indicated by foetal scalp electrodes. Patients were classified into AT (ritodrine hydrochloride approximately 500 µg/min) and control groups with 15 and 12 participants, respectively. FHR patterns, Apgar scores, umbilical arterial analysis, and neonatal admission were compared. All participants had FHR category II; decelerations disappeared in all foetuses in the AT group, with no significant difference in neonatal outcomes. The AT group had a higher baseline FHR and lower short-term FHR variability than the control group, indicating foetal autonomic responses. Further studies are needed to clarify the effects of AT on FHR patterns, neonatal outcomes, and foetal and neonatal autonomic responses.Impact statementWhat is already known on this subject? The usefulness of acute tocolysis using ritodrine hydrochloride has been well-documented in several studies; however, such an application often induces side effects, such as maternal tachycardia, palpitations, and tremors.What the results of this study add? The short-term administration of ritodrine hydrochloride eliminated decelerations, with no significant difference in neonatal outcomes in pregnant women with foetal heart rate category II. Meanwhile, there were higher foetal heart rate and lower short-term foetal heart rate variability in pregnant women administered with ritodrine hydrochloride, indicating foetal autonomic responses.What the implications are of these findings for clinical practice and/or further research? Ritodrine hydrochloride administration, even for short-term, appears to be associated with foetal autonomic responses. Further studies with stratification of patient groups based on the severity and aetiology of non-reassuring foetal status, including pregnant women with foetal category III, would elucidate the risk and benefit of acute tocolysis using ritodrine hydrochloride, based on foetal heart rate patterns, neonatal outcomes, and foetal and neonatal autonomic responses.

Acute tocolysis for uterine tachysystole or suspected fetal distress

BACKGROUND

Uterine tachysystole (more than 5 contractions per 10 minutes in 2 consecutive intervals) is common during labour, particularly with use of labour-stimulating agents. Tachysystole may reduce fetal oxygenation by interrupting maternal blood flow to the placenta during contractions. Reducing uterine contractions may improve placental blood flow, improving fetal oxygenation. This review aimed to evaluate the use of tocolytics to reduce or stop uterine contractions for improvement of the condition of the fetus in utero. This new review supersedes an earlier Cochrane Review on the same topic.

OBJECTIVES

To assess the effects of the use of acute tocolysis during labour for uterine tachysystole or suspected fetal distress, or both, on fetal, maternal and neonatal outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform (ICTRP) (2 February 2018), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating acute tocolysis for uterine tachysystole, intrapartum fetal distress, or both.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane.

MAIN RESULTS

We included eight studies (734 women), conducted in hospital settings, predominantly in high-income countries (USA, Austria, Uruguay). Two trials were conducted in upper and lower middle-income countries (South Africa, Sri Lanka). The hospital facilities all had the capacity to perform caesarean section. Overall, the studies had a low risk of bias, except for methods to maintain blinding. All of the trials used a selective beta₂ (ß₂)-adrenergic agonist in one arm, however the drug used varied, as did the comparator. Limited information was available on maternal outcomes.Selective ß₂-adrenergic agonist versus no tocolytic agent, whilst awaiting emergency deliveryThere were two stillbirths, both in the no tocolytic control group (risk ratio (RR) 0.23, 95% confidence interval (CI) 0.01 to 4.55; 2 studies, 57 women; low-quality evidence). One had gross hydrocephalus and the second occurred with vaginal delivery after waiting 55 minutes for caesarean section. The decision for caesarean section delivery was an inclusion criterion in both studies so we could not assess this as an outcome under this comparison. Abnormal fetal heart trace is probably lower with tocolytic treatment (RR 0.28, 95% CI 0.08 to 0.95; 2 studies, 43 women; moderate-quality evidence). The effects on the number of babies with Apgar score below seven were uncertain (low-quality evidence).Intravenous (IV) atosiban versus IV hexoprenaline (1 study, 26 women) One infant in the hexoprenaline group required > 24 hours in the neonatal intensive care unit (NICU) following a forceps delivery (RR 0.33, 95% CI 0.01 to 7.50; low-quality evidence). There were no fetal or neonatal mortalities and no Apgar scores below seven. There was one caesarean delivery in the IV hexoprenaline group (RR 0.33, 95% CI 0.01 to 7.50; low-quality evidence), and one case of abnormal fetal heart score in the atosiban group (RR 3.00, 95% CI 0.13 to 67.51; very low-quality evidence).IV fenoterol bromhydrate versus emergency delivery (1 study, 390 women) No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. IV fenoterol probably increases the risk of caesarean delivery (RR 1.12, 95% CI 1.04 to 1.22; moderate-quality evidence). Fenoterol may have little or no effect on the risk of Apgar scores below seven (RR 1.28, 95% CI 0.35 to 4.68; low-quality evidence).IV hexoprenaline versus no tocolytic agent, whilst awaiting emergency delivery (1 study, 37 women) No data were reported for perinatal death or severe morbidity. There were two fetal deaths in the no tocolytic control group (RR 0.23, 95% CI 0.01 to 4.55; low-quality evidence). The rate of caesarean delivery was not reported. There were two babies with Apgar scores below seven in the control group and none in the hexoprenaline group (RR 0.24, 95% CI 0.01 to 4.57; 35 women; low-quality evidence).Subcutaneous terbutaline versus IV magnesium sulphate (1 study, 46 women)No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. The decision for caesarean section was an inclusion criterion, so we could not assess this. The effects on abnormal fetal heart trace are uncertain (very low-quality evidence).Subcutaneous terbutaline with continuation of oxytocic infusion versus cessation of oxytocic infusion without tocolytic agent (1 study, 28 women) No data were reported for perinatal death, severe morbidity or fetal or neonatal mortality. There may be little or no difference in the rates of caesarean delivery in the subcutaneous terbutaline (8/15) and control groups (4/13) (RR 1.73, 95% CI 0.68 to 4.45; low-quality evidence). There were no cases of Apgar scores below seven or abnormal fetal heart trace.Subcutaneous terbutaline versus no tocolytic agent, whilst awaiting emergency delivery (1 study, 20 women) No data were reported for perinatal death or severe morbidity. There were no fetal or neonatal mortalities. The decision for caesarean section was an inclusion criterion, so we could not assess this. There were two babies with Apgar scores below seven in the control group and none in the terbutaline group (RR 0.17, 95% CI 0.01 to 3.08; low-quality evidence).IV terbutaline versus IV nitroglycerin (1 study, 110 women)No data were reported for perinatal death or severe morbidity or fetal or neonatal mortality. There may be little or no difference in the rates of caesarean delivery between the IV terbutaline (30/57) and control groups (29/53) (RR 0.96, 95% CI 0.68 to 1.36; low-quality evidence). There were no cases of Apgar scores below seven.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the effects of tocolytics for uterine tachysystole or suspected fetal distress during labour. The clinical significance for some of the improvements in measures of fetal well-being with tocolytics is unclear. The sample sizes were too small to detect effects on neonatal morbidity, mortality or serious adverse effects. The majority of studies are from high-income countries in facilities with access to caesarean section, which may limit the generalisability of the results to lower-resource settings, or settings where caesarean section is not available.Further well-designed and adequately powered RCTs are required to evaluate clinically relevant indicators of maternal and neonatal morbidity and mortality.

Interventions for Intrauterine Resuscitation in Suspected Fetal Distress During Term Labor: A Systematic Review

IMPORTANCE

Intrauterine resuscitation techniques during term labor are commonly used in daily clinical practice. Evidence, however, to support the beneficial effect of intrauterine resuscitation techniques on fetal distress during labor is limited and sometimes contradictory. In contrast, some of these interventions may even be harmful.

OBJECTIVE

To give insight into the current evidence on intrauterine resuscitation techniques. In addition, we formulate recommendations for current clinical practice and propose directions for further research.

EVIDENCE ACQUISITION

We systematically searched the electronic PubMed, EMBASE, and CENTRAL databases for studies on intrauterine resuscitation for suspected fetal distress during term labor until February 2015. Eligible articles and their references were independently assessed by 2 authors. Judgment was based on methodological quality and study results.

RESULTS

Our literature search identified 15 studies: 4 studies on amnioinfusion, 1 study on maternal hyperoxygenation, 1 study on maternal repositioning, 1 study on intravenous fluid administration, and 8 studies on tocolysis. Of these 15 research papers, 3 described a randomized controlled trial; all other studies were observational reports or case reports.

CONCLUSIONS AND RELEVANCE

Little robust evidence to promote a specific intrauterine resuscitation technique is available. Based on our literature search, we support the use of tocolysis and maternal repositioning for fetal distress. We believe the effect of amnioinfusion and maternal hyperoxygenation should be further investigated in properly designed randomized controlled trials to make up the balance between beneficial and potential hazardous effects.

Antenatal exposure to indomethacin increases the risk of severe intraventricular hemorrhage, necrotizing enterocolitis, and periventricular leukomalacia: a systematic review with metaanalysis

OBJECTIVE

The purpose of this study was to provide an updated summary of the literature regarding the effects of tocolysis with indomethacin on neonatal outcome by systematically reviewing previously and recently reported data.

STUDY DESIGN

All previously reported studies pertaining to indomethacin tocolysis and neonatal outcomes along with recently reported data were identified with the use of electronic databases that had been supplemented with references that were cited in original studies and review articles. Observational studies that compared neonatal outcomes among preterm infants who were exposed and not exposed to indomethacin were included in this systematic review. Data were extracted and quantitative analyses were performed on those studies that assessed the neonatal outcomes of patients that received antenatal tocolysis with indomethacin.

RESULTS

Twenty-seven observational studies that met criteria for systematic review and metaanalysis were identified. These studies included 8454 infants, of whom 1731 were exposed to antenatal indomethacin and 6723 were not exposed. Relative risks with 95% confidence intervals were calculated for dichotomous outcomes with the use of random and fixed-effects models. Metaanalysis revealed no statistically significant differences in the rates of respiratory distress syndrome, patent ductus arteriosus, neonatal mortality rate, neonatal sepsis, bronchopulmonary dysplasia, or intraventricular hemorrhage (all grades). However, antenatal exposure to indomethacin was associated with an increased risk of severe intraventricular hemorrhage (grade III-IV based on Papile's criteria; relative risk, 1.29; 95% confidence interval, 1.06-1.56), necrotizing enterocolitis (relative risk, 1.36; 95% confidence interval, 1.08-1.71), and periventricular leukomalacia (relative risk, 1.59; 95% confidence interval, 1.17-2.17).

CONCLUSION

The use of indomethacin as a tocolytic agent for preterm labor is associated with an increased risk for severe intraventricular hemorrhage, necrotizing enterocolitis, and periventricular leukomalacia.

Oxytocin receptor antagonists for inhibiting preterm labour

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Use of an oxytocin antagonist in in vitro fertilization-embryo transfer for women with repeated implantation failure: a retrospective study

OBJECTIVE

This retrospective study aimed to investigate the use of an oxytocin antagonist in improving the pregnancy outcome of in vitro fertilization-embryo transfer (IVF-ET) in patients with repeated implantation failure (RIF).

MATERIALS AND METHODS

A total of 150 infertile couples with RIF undergoing IVF-ET were divided into three groups. Patients who did not receive atosiban were used as controls (Group 1; n=80). Forty patients received a single bolus dose (6.75mg, 0.9mL/vial) of atosiban before ET (Group 2), and 30 patients received a bolus dose of 6.75mg atosiban followed by infusion at 18mg/hr for 3 hours immediately after ET (Group 3).

RESULTS

A significantly higher implantation rate (30.21%) was noted in Group 2 compared with Groups 1 and 3 (11.8% and 15.9%, respectively; p=0.0006). The clinical pregnancy rate of Group 2 (37.5%) was significantly higher than that of Groups 1 (12.5%) and 3 (20%) (p=0.0057). The live birth rate was significantly higher in Group 2 (35%) than in Groups 1 and 3 (10% and 16.67%, respectively; p=0.0031).

CONCLUSION

These results suggest that IVF-ET using lower dosage of atosiban may improve pregnancy outcomes of patients with RIF.

Atosiban vs. ritodrine as a tocolytic in external cephalic version at term: a prospective cohort study

OBJECTIVE

To compare the success rate of external cephalic version (ECV) at term using ritodrine or atosiban as a tocolytic agent.

STUDY DESIGN

Prospective cohort study with a sample of 236 pregnant women with a breech presentation at term, from November 2006 to March 2008. Data have been analyzed from the moment the cephalic version is performed until the time of delivery.

RESULTS

ECV success rate using ritodrine as a tocolytic agent was 56.8% compared to 31.4% with atosiban. Ritodrine increases the version success potential more significantly than atosiban (P<0.05). In both cases, the use of ECV reduced the rate of cesarean sections, although a higher number of versions are required with atosiban [numbers needed to treat (NNT)=9.08] to avoid a cesarean section compared to ritodrine (NNT=3.41).

CONCLUSIONS

Ritodrine seems better than atosiban as tocolytic agent for ECVs.

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.