BACKGROUND: Many maternal deaths across the world result from complications of the third stage of labour (when the placenta is delivered). OBJECTIVES: To examine the effect of oxytocin given prophylactically in the third stage of labour on maternal and neonatal outcomes. SEARCH STRATEGY: Relevant trials were identified in the Cochrane Collaboration Controlled Trials Register and the Pregnancy and Childbirth Review Group's Specialised Register of Controlled Trials. Date of last search: May 2001. SELECTION CRITERIA: All acceptably randomised or quasi-randomised controlled trials including pregnant women anticipating a vaginal delivery where oxytocin was given prophylactically for the third stage of labour. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed studies for relevance and methodological quality, and extracted data. Analysis was by intention to treat. Subgroup analyses were based on extent of selection bias, oxytocin in the context of active or expectant management of the third stage, and timing of administration. Results are presented as relative risks, and weighted mean difference, both with 95% confidence intervals using a fixed effects model. MAIN RESULTS: In seven trials involving over 3000 women in hospital and/or developed country settings, prophylactic oxytocin showed benefits (reduced blood loss (relative risk (RR) for blood loss > 500 ml 0.50; 95% confidence interval (CI) 0.43, 0.59) and need for therapeutic oxytocics (RR 0.50; 95% CI 0.39, 0.64).) compared to no uterotonics, although there was a non-significant trend towards more manual removal of the placenta (RR 1.17; 95% CI 0.79, 1.73) which was most marked in the expectant management subgroup, and blood transfusions (RR 1.30; 95% CI 0.50, 3.39) in the trials with more manual removals of the placenta). In six trials involving over 2800 women, there was little evidence of differential effects for oxytocin versus ergot alkaloids, except ergot alkaloids are associated with more manual removals of the placenta (RR 0.57; 95% CI 0.41, 0.79), and with the suggestion of more raised blood pressure (RR 0.53; 95% CI 0.19, 1.58) than with oxytocin. In five trials involving over 2800 women, there was little evidence of a synergistic effects of adding oxytocin to ergometrine versus ergometrine alone. For all other outcomes in the comparisons either there are no data or the number of adverse events is very small, and so definite conclusions cannot be drawn. REVIEWER'S CONCLUSIONS: There are strong suggestions of benefit for oxytocin in terms of postpartum haemorrhage, and the need for therapeutic oxytocics, but without sufficient information about other outcomes and side-effects it is difficult to be confident about the trade-offs for these benefits, especially if the risk of manual removal of the placenta may be increased. There seems little evidence in favour of ergot alkaloids alone compared to either oxytocin alone, or to Syntometrine, but the data are sparse. More trials are needed in domiciliary deliveries in developing countries, which shoulder most of the burden of third stage complications.