David M Haas, Amanda M Morgan, Samantha J Deans, Frank P Schubert

Preterm birth is the leading cause of death and disability in newborns worldwide. A wide variety of tocolytic agents have been utilized to delay birth for women in preterm labor. One of the earliest tocolytics utilized for this purpose was ethanol infusion, although this is not generally used in current practice due to safety concerns for both the mother and her baby. To determine the efficacy of ethanol in stopping preterm labor, preventing preterm birth, and the impact of ethanol on neonatal outcomes. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 May 2015) and reference lists of retrieved studies. We included randomized and quasi-randomized studies. Cluster-randomized trials and cross-over design trials were not eligible for inclusion. We only included studies published in abstract form if there was enough information on methods and relevant outcomes. Trials were included if they compared ethanol infusion to stop preterm labor versus placebo/control or versus other tocolytic drugs. At least two review authors independently assessed studies for inclusion and risk of bias. At least two review authors independently extracted data. Data were checked for accuracy. Twelve trials involving 1586 women met inclusion criteria for this review. One trial did not report on the outcomes of interest in this review.Risk of bias of included studies: The included studies generally were of low quality based on inadequate reporting of methodology. Only three trials had low risk of bias for random sequence generation and one had low risk of bias for allocation concealment and participant blinding. Most studies were either high risk of bias or uncertain in these key areas. Comparison 1: Ethanol versus placebo/control (two trials, 77 women) Compared to controls receiving pain medications and dextrose solution, ethanol did not improve any of the primary outcomes: birth < 48 hours after trial entry (one trial, 35 women; risk ratio (RR) 0.93, 95% confidence interval (CI) 0.43 to 2.00), or neonatal mortality (one trial, 35 women; RR 1.06, 95% CI 0.31 to 3.58). Serious maternal adverse events and perinatal mortality were not reported by either of the two trials in this comparison. Maternal adverse events (overall) were not reported but one trial (42 women) reported that there were no maternal adverse events that required stopping or changing drug) in either group. One trial did report delay until delivery but this outcome was reported as a median with no mention of the standard deviation (median 19 days in ethanol group versus "less than 1" day in the glucose/water group). There were no differences in any secondary outcomes reported: preterm birth < 34 weeks or < 37 weeks; serious infant outcome; fetal alcohol syndrome/fetal alcohol spectrum disorder; or small-for-gestational age. Comparison 2: Ethanol versus other tocolytic (betamimetics) (nine trials, 1438 women) Compared to betamimetics (the only tocolytic used as a comparator in these studies), ethanol was associated with no clear difference in the rate of birth < 48 hours after trial entry (two trials, 130 women; average RR 1.12, 95% CI 0.53 to 2.37, Tau² = 0.19, I² = 59%), similar rates of perinatal mortality (six trials, 698 women; RR1.20, 95% CI 0.78 to 1.84), higher rates of neonatal mortality (eight trials, 1238 women; RR 1.43, 95% CI 1.02 to 2.02), higher rates of preterm birth < 34 weeks (two trials, 599 women; RR 1.56, 95% CI 1.11 to 2.19), higher rates of neonatal respiratory distress syndrome (three trials, 823 women; RR 1.76, 95% CI 1.33 to 2.33), and higher rates of low birthweight babies < 2500 g (five trials, 834 women; RR 1.30, 95% CI 1.09 to 1.54). These outcomes are likely all related to the lower incidence of preterm birth seen with other tocolytics, which for all these comparisons were betamimetics. Serious maternal adverse events were not reported in any of the nine trial reports. However, ethanol had a trend towards a lower rate of maternal adverse events requiring stopping or changing the drug (three trials, 214 women; RR 0.25, 95% CI 0.06 to 0.97). There were no differences in other secondary outcomes of preterm birth < 37 weeks, number of days delivery was delayed, or overall maternal adverse events.Planned sensitivity analysis, excluding quasi-randomized trials did not substantially change the results of the primary outcome analyses with the exception of neonatal mortality which no longer showed a clear difference between the ethanol and other tocolytic groups (3 trials, 330 women; RR 1.49, 95% CI 0.82 to 2.72). This review is based on evidence from twelve studies which were mostly low quality. There is no evidence that to suggest that ethanol is an effective tocolytic compared to placebo. There is some evidence that ethanol may be better tolerated than other tocolytics (in this case betamimetics), but this result is based on few studies and small sample size and therefore should be interpreted with caution. Ethanol appears to be inferior to betamimetics for preventing preterm birth in threatened preterm labor.Ethanol is generally no longer used in current practice due to safety concerns for the mother and her baby. There is no need for new studies to evaluate the use of ethanol for preventing preterm birth in threatened preterm labour. However, it would be useful for long-term follow-up studies on the babies born to mothers from the existing studies in order to assess the risk of long-term neurodevelopmental status.