The perineum is the triangular area of skin between the back of the vagina and the front of the rectum or anal canal. The importance of the perineum is not the actual skin but the muscles and fibrous tissue that lie beneath the skin. These are known as the perineal muscles and they extend from each side of the pelvis to join together in the mid-line. The muscles vary in strength from person to person and under normal circumstances they strengthen the posterior wall of the vagina and close the vaginal entrance, giving support to the vagina and the pelvic floor.
The perineum is stretched and may be injured, damaged or torn during the delivery of a baby. To avoid this tearing, or perineal laceration, an incision is usually made in the perineum to enlarge the vaginal entrance during delivery. This is known as an episiotomy. Any tear or incision in the perineum is repaired immediately after delivery.