Background: For centuries, there has been controversy around whether being upright (sitting, birthing stools, chairs, squatting, kneeling) or lying down (lateral (Sim's) position, semi-recumbent, lithotomy position, Trendelenburg's position) have advantages for women giving birth to their babies. This is an update of a review previously published in 2012, 2004 and 1999. Objectives: To determine the possible benefits and risks of the use of different birth positions during the second stage of labour without epidural anaesthesia, on maternal, fetal, neonatal and caregiver outcomes. Search methods: We searched Cochrane Pregnancy and Childbirth's Trials Register (30 November 2016) and reference lists of retrieved studies. Selection criteria: Randomised, quasi-randomised or cluster-randomised controlled trials of any upright position assumed by pregnant women during the second stage of labour compared with supine or lithotomy positions. Secondary comparisons include comparison of different upright positions and the supine position. Trials in abstract form were included. Data collection and analysis: Two review authors independently assessed trials for inclusion and assessed trial quality. At least two review authors extracted the data. Data were checked for accuracy. The quality of the evidence was assessed using the GRADE approach. Main results: Results should be interpreted with caution because risk of bias of the included trials was variable. We included eleven new trials for this update; there are now 32 included studies, and one trial is ongoing. Thirty trials involving 9015 women contributed to the analysis. Comparisons include any upright position, birth or squat stool, birth cushion, and birth chair versus supine positions. In all women studied (primigravid and multigravid), when compared with supine positions, the upright position was associated with a reduction in duration of second stage in the upright group (MD -6.16 minutes, 95% CI -9.74 to -2.59 minutes; 19 trials; 5811 women; P = 0.0007; random-effects; I2; = 91%; very low-quality evidence); however, this result should be interpreted with caution due to large differences in size and direction of effect in individual studies. Upright positions were also associated with no clear difference in the rates of caesarean section (RR 1.22, 95% CI 0.81 to 1.81; 16 trials; 5439 women; low-quality evidence), a reduction in assisted deliveries (RR 0.75, 95% CI 0.66 to 0.86; 21 trials; 6481 women; moderate-quality evidence), a reduction in episiotomies (average RR 0.75, 95% CI 0.61 to 0.92; 17 trials; 6148 women; random-effects; I2; = 88%), a possible increase in second degree perineal tears (RR 1.20, 95% CI 1.00 to 1.44; 18 trials; 6715 women; I2; = 43%; low-quality evidence), no clear difference in the number of third or fourth degree perineal tears (RR 0.72, 95% CI 0.32 to 1.65; 6 trials; 1840 women; very low-quality evidence), increased estimated blood loss greater than 500 mL (RR 1.48, 95% CI 1.10 to 1.98; 15 trials; 5615 women; I2; = 33%; moderate-quality evidence), fewer abnormal fetal heart rate patterns (RR 0.46, 95% CI 0.22 to 0.93; 2 trials; 617 women), no clear difference in the number of babies admitted to neonatal intensive care (RR 0.79, 95% CI 0.51 to 1.21; 4 trials; 2565 infants; low-quality evidence). On sensitivity analysis excluding trials with high risk of bias, these findings were unchanged except that there was no longer a clear difference in duration of second stage of labour (MD -4.34, 95% CI -9.00 to 0.32; 21 trials; 2499 women; I2; = 85%). The main reasons for downgrading of GRADE assessment was that several studies had design limitations (inadequate randomisation and allocation concealment) with high heterogeneity and wide CIs. Authors' conclusions: The findings of this review suggest several possible benefits for upright posture in women without epidural anaesthesia, such as a very small reduction in the duration of second stage of labour (mainly from the primigravid group), reduction in episiotomy rates and assisted deliveries. However, there is an increased risk blood loss greater than 500 mL and there may be an increased risk of second degree tears, though we cannot be certain of this. In view of the variable risk of bias of the trials reviewed, further trials using well-designed protocols are needed to ascertain the true benefits and risks of various birth positions.