Abstract: We included 62 trials (6428 women). Twenty-two trials did not contribute data to the meta-analyses. The trials were generally small and of limited quality. Three trials (107 women) indicated that bromocriptine significantly reduced the proportion of women lactating compared with no treatment at or within seven days postpartum (three trials, 107 women; risk ratio (RR) 0.36, 95% confidence interval (CI) 0.24 to 0.54). Seven trials involving oestrogen preparations (diethylstilbestrol, quinestrol, chlorotrianisene, hexestrol) suggested that they significantly reduced the proportion of lactating women compared with no treatment at or within seven days postpartum (RR 0.40, 95% CI 0.29 to 0.56). We found no trials comparing non-pharmacologic methods with no treatment. Trials comparing bromocriptine with other pharmacologic agents such as methergoline, prostaglandins, pyridoxine, carbegoline, diethylstilbestrol and cyclofenil suggested similarity in their effectiveness. Side effects were poorly reported in the trials and no case of thromboembolism was recorded in the four trials that reported it as an outcome. There is weak evidence that some pharmacologic treatments (most of which are currently unavailable to the public) are better than no treatment for suppressing lactation symptoms in the first postpartum week. No evidence currently exists to indicate whether non-pharmacologic approaches are more effective than no treatment. Presently, there is insufficient evidence to address the side effects of methods employed for suppressing lactation. When women desire treatment, bromocriptine may be considered where it is registered for lactation suppression in those without predisposition to its major side effects of public concerns. Many trials did not contribute data that could be included in analyses. Large randomised trials are needed to compare the effectiveness of pharmacologic (especially bromocriptine) and non-pharmacologic methods with no treatment. Such trials should consider the acceptability of the intervention and lactation symptoms of concern to women and be large enough to detect clinically important differences in major side effects between comparison groups.

Plain-language summary: The evidence to support treatments for preventing lactation is limited. The review authors identified 62 controlled trials that randomised a total of 6428 mothers to receive the treatment under investigation, no treatment or another treatment. Twenty-two trials did not contribute data to the meta-analyses. The trials were generally of limited quality and most were conducted among healthy women who chose not to breastfeed for personal reasons at hospitals in industrialised countries before 1980. Half of the trials involved bromocriptine. Two trials (107 women) reported that taking bromocriptine was better than no treatment in suppressing lactation in the first week after giving birth. The 11 trials using oestrogen preparations (diethylstilbestrol, quinestrol, chlorotrianisene, hexestrol) also showed suppression of lactation. A combination of testosterone and oestrogen preparations was of some benefit in reducing symptoms in three trials (436 women). Other pharmacologic agents (clomiphene, tamoxifen, prostaglandins, pyridoxine, oxytocin, L-dopa and homeopathic preparation) were tested in single small trials. Generally, side effects were poorly reported and no case of thromboembolism was recorded among trials that included it as an adverse treatment outcome. Most of the drugs tested are currently not available or registered for suppressing lactation. No trials compared non-drug approaches with no treatment and none of the included trials provided reliable data on women’s satisfaction with the treatment.