Lateral episiotomy is a current care practiced with childbirth room. One of the problems encountered with this surgical act is the residual pain on perineal scar level. Maximal during the first 24 hours, this pain can persist several days or several weeks hampering to variable degrees a normal recovery of autonomy and comfort of life. Some studies have shown the interest of ropivacaine, local anaesthetic with a long action's duration for proctologic surgeries and for the cure of inguinal hernia. A recent study shown the ropivacaine perineal infiltration used prior perineorrhaphy allows an absence of post-partum pain for 24 to 27% of cases and a first analgesics request delayed to ten hours.