Aims To assess the effects of upright positions on maternal outcomes for women without epidural analgesia in comparison with recumbent positions during the second stage of labour. Background Upright positions have many physiological advantages. The underlying benefits and risks of upright positions during the second stage of labour have been reported in many studies but the results are divergent. Design A meta-analysis of randomized controlled trials. Data sources The Cochrane Library, PubMed, Embase, CINAHL and ProQuest databases were systematically searched from inception to 17 June 2019. Review methods We conducted the quality appraisal using the Cochrane Collaboration's tool and performed meta-analyses using the Review Manager 5.3 software. The primary outcomes were instrumental vaginal delivery and the duration of the second stage of labour. Results Overall, 12 studies including 4,314 women were included. Upright positions significantly decreased the rate of instrumental vaginal delivery (risk ratio [RR] = 0.74, 95% CI 0.59-0.93), shortened the active pushing phase (mean difference [MD] = -8.16 min, 95% CI -16.29 to -0.02), decreased the rate of severe perineal trauma (RR = 0.35, 95% CI 0.14-0.87) and episiotomy (RR = 0.52, 95% CI 0.29-0.92), but significantly increased the rate of second-degree perineal trauma (RR = 1.45, 95% CI 1.10-1.90). However, there was no significant difference in the duration of the second stage of labour or postpartum haemorrhage. Conclusions Upright positions are beneficial for improving maternal outcomes. Several results should be considered with caution. Researchers need to clarify the definition of upright positions and conduct large, robust studies in the future to provide stronger evidence. Impact This meta-analysis explores a crucial issue in intrapartum care and clarifies the benefits and possible risks of upright positions in the second stage of labour. Midwives and obstetricians are encouraged to apply upright positions depending on women's preferences and labour progress but should take measures to prevent perineal trauma.