Background Women who are undelivered after 48 hours of tocolysis remain at increased risk of preterm labour, but it is not clear whether prolonged treatment is effective. Objective To review the current evidence for the effectiveness of maintenance tocolysis. Methods The results of published systematic reviews were summarised. Results Four systematic reviews and two trials published too recently for inclusion were identified. Maintenance tocolysis with -agonists and magnesium sulphate was ineffective in prolonging gestation or reducing any adverse fetal outcomes. One trial of maintenance tocolysis with nifedipine was underpowered to rule out an effect on prolonging gestation. One trial using the oxytocin receptor blocker, atosiban, showed that this drug used as maintenance tocolysis does prolong gestation, but the trial was too small to demonstrate any reduction in substantive fetal outcomes. Conclusions There is insufficient evidence to justify the routine use of maintenance tocolysis in preterm labour. It remains plausible that prolongation of gestation might be beneficial in selected cases of very preterm labour where fetal compromise and infection have been ruled out. The only tocolytic that has been shown to prolong gestation when used as maintenance therapy is atosiban.