An episiotomy is a surgical incision made to enlarge the vaginal opening during childbirth to assist delivery of the baby. This incision can be midline or at an angle from the posterior end of the vulva. It should be performed under local anaesthetic and should, of course, be sutured closed after delivery.
Proponents of episiotomies say it helps to lessen perineal trauma, minimize postpartum pelvic floor dysfunction, reduce blood loss at delivery, and protect against neonatal trauma.
Current medical thinking is that routine episiotomies are probably unnecessary and only bring about increased morbidity. There are studies showing that episiotomies did not, in fact, reduce the incidence of serious perineal lacerations but increased them.
Having an episiotomy will result in significant perineal pain in the postpartum period. This can result in trouble with urinating or defecating, much to the new mother's despair.
Episiotomies definitely should not be a routine procedure and will probably end up being practiced less and less often as time goes on, much like circumcision. Until then, the social entrenchment of belief in this procedure will ensure that it continues being performed far more often than it should.
Having said all that, episiotomies may well be indicated if there is any sign of fetal distress while the baby is in the birth canal and there is a clinical indication to get the baby out as soon as possible.
The evidence is sketchy for perineal massage actually working to prevent birth trauma but I guess it can't hurt if done correctly ... | 
