Antispasmodics for labour

A woman who is in active labour for too long (usually set at more than 12 hours) is at risk of becoming exhausted and developing complications such as infection and excessive bleeding. The unborn baby can also be harmed, showing distress and low oxygenation (asphyxia). It is common practice to intervene in the labouring process to avoid this by rupturing membranes (breaking the waters), giving medications to speed up contractions and providing ongoing support. Antispasmodics are drugs that are usually taken to relieve cramps. They work either by direct relaxation of muscle or by interfering with the message sent by the nerves to the muscle to contract. It is thought that these drugs may help with opening the womb (dilatation of the cervix), when given during labour as a preventative or a treatment strategy. This would shorten the time spent in labour. Evidence was sought to support this idea. Twenty-one randomised controlled studies with a total of 3286 participants were included. The data were combined in an analysis to get an overall result. All types of antispasmodics were given at the beginning of established labour. They decreased the first stage of labour, the time from beginning of labour until the baby is about to be born, by 49 to 98 minutes, as well as the total duration of labour, from the beginning of labour until the delivery of the afterbirth, by 49 to 121 minutes. The drugs did not affect the number of women requiring emergency caesarean sections and did not have serious side effects for either mother or her baby. The most commonly reported adverse events for the mothers were fast heart rates and mouth dryness, but since both maternal and neonatal adverse events were poorly reported, more information is needed to make conclusions about the safety of these drugs during labour. The included studies were mostly of poor quality and good studies are needed to assess what happens when these drugs are given to women whose labour is already prolonged.

Authors' conclusions: 

There is low quality evidence that antispasmodics reduce the duration of first stage of labour and increase the cervical dilatation rate. There is very low quality evidence that antispasmodics reduce the total duration of labour. There is moderate quality evidence that antispasmodics do not affect the rate of normal vertex deliveries. There is insufficient evidence to make any conclusions regarding the safety of these drugs for both mother and baby. Large, rigorous randomised controlled trials are needed to evaluate the effect of antispasmodics on prolonged labour and to evaluate their effect on labour in a context of expectant management of labour.

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Background: 

Prolonged labour can lead to increased maternal and neonatal mortality and morbidity due to increased risks of maternal exhaustion, postpartum haemorrhage and sepsis, fetal distress and asphyxia and requires early detection and appropriate clinical response. The risks for complications of prolonged labour are much greater in poor resource settings. Active management of labour versus physiological, expectant management, has shown to decrease the occurrence of prolonged labour. Administering antispasmodics during labour could also lead to faster and more effective dilatation of the cervix. Interventions to shorten labour, such as antispasmodics, can be used as a preventative or a treatment strategy in order to decrease the incidence of prolonged labour. As the evidence to support this is still largely anecdotal around the world, there is a need to systematically review the available evidence to obtain a valid answer.

Objectives: 

To assess the effects of antispasmodics on labour in term pregnancies.

Search strategy: 

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (28 February 2013), the ProQuest dissertation and thesis database, the dissertation database of the University of Stellenbosch and Google Scholar (28 February 2013) and reference lists of articles. We also contacted pharmaceutical companies and experts in the field. We did not apply language restrictions.

Selection criteria: 

Randomised controlled trials comparing antispasmodics with placebo or no medication in women with term pregnancies.

Data collection and analysis: 

Two review authors independently screened abstracts and selected studies for inclusion, assessed risk of bias and extracted data. Data were checked for accuracy. We contacted trial authors when data were missing.

Main results: 

Twenty-one trials (n = 3286) were included in the review. Seventeen trials (n = 2617) were included in the meta-analysis. Antispasmodics used included valethamate bromide, hyoscine butyl-bromide, drotaverine hydrochloride, rociverine and camylofin dihydrochloride. Most studies included antispasmodics as part of their package of active management of labour. Overall, the quality of studies was poor, as only four trials were assessed as low risk of bias. Thirteen trials (n = 1995) reported on the duration of first stage of labour, which was significantly reduced by an average of 74.34 minutes when antispasmodics were administered (mean difference (MD) -74.34 minutes; 95% confidence Interval (CI) -98.76 to -49.93). Seven studies (n = 797) reported on the total duration of labour, which was significantly reduced by an average of 85.51 minutes (MD -85.51 minutes; 95% CI -121.81 to -49.20). Six studies (n = 820) had data for the outcome: rate of cervical dilatation. Administration of antispasmodics significantly increased the rate of cervical dilatation by an average of 0.61 cm/hour (MD 0.61 cm/hour; 95% CI 0.34 to 0.88). Antispasmodics did not affect the duration of second and third stage of labour. The rate of normal vertex deliveries was not affected either. Only one study explored pain relief following administration of antispasmodics and no conclusions can be drawn on this outcome. There was significant heterogeneity for most outcomes and therefore, we undertook random-effects meta-analysis. Subgroup analysis was undertaken to explore heterogeneity, but remained largely unexplained. Maternal and neonatal adverse events were reported inconsistently. The main maternal adverse event reported was tachycardia. No serious neonatal adverse events were reported.

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