Abstract: 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. 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.

Plain-language summary: 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.