Better perineal outcomes in sitting birthing position cannot be explained by changing from upright to supine position for performing an episiotomy

women who give birth in supine position are more likely to have an episiotomy than women who give birth in sitting position. A confounding effect may be that women in upright positions in second stage of labour are asked to lie down if a professional needs to perform an episiotomy. This prospective cohort study aimed to determine whether this factor can explain the lower rate of episiotomy in sitting compared to supine position. data from 1196 women who had a spontaneous, vaginal birth were analysed. Positions during second stage and at birth were carefully recorded. Three groups of birthing positions were compared in multivariable analyses: 1) horizontal during second stage and supine at birth (horizontal/supine), 2) horizontal and upright during second stage and supine at birth (various/supine), 3) sitting at birth regardless of the position in second stage. Logistic regression analysis was used to adjust for known risk factors for perineal damage. women in sitting position at birth compared to those in the horizontal/supine group had a lower episiotomy rate (adjusted OR 0.28;95%-CI 0.14-0.56) and a non-significant higher intact perineum rate (adjusted OR 1.40, 95% CI 0.96-2.04). Women in the various/supine group compared to the horizontal/supine group had a similar episiotomy rate (adjusted OR 1.12;95%-CI 0.69-1.83). we did not confirm our hypothesis that more women in supine compared to sitting position have an episiotomy because women in upright position are asked to lie down if an episiotomy is necessary