An episiotomy is a surgical incision into the body of the perineum which is the space between the vaginal opening and the anus. An episiotomy is used to hasten the delivery, particularly in the case where the baby needs to get out quickly. Also, if the baby is experiencing any kind of distress, making that incision will make the opening larger and help the baby deliver more quickly. An episiotomy used to be done routinely and it used to be thought that the women would recover better from an episiotomy incision rather than a natural tear. It used to be thought that the woman could not give birth safely without an episiotomy. We now know from decades of research that an episiotomy, without indication, is very harmful to the mother's tissues and very harmful to her pelvic floor musculature. So now the common belief is to only use it if the baby is in distress and needs to get out very quickly. Sometimes it also might need to be used if the delivery is instrumental in anyway in that if the baby needs to be delivered by forceps or vacuum extraction. Sometimes an episiotomy is necessary in order to give more room for maneuver ability of those instruments.
