Episiotomy
An episiotomy is an incision made into the perineum from the vaginal opening to facilitate vaginal delivery.
It used to be a routine procedure historically, but it is now performed uncommonly, and only in specific situations, as many studies have shown that less suturing is generally needed with naturally-occurring tears.
Situations where an episiotomy may be required are:
If the fetal well-being is in question (eg. prolonged drop of the fetal heart rate) and the only thing impeding delivery is a tight perineum.
When the perineum is very tight and not stretching well, and causing crowning to be very prolonged, or when the maternal tissues are threatening to tear badly in multiple directions.
When an assisted vaginal delivery (mainly forceps) is required.