In order to determine the optimal angle to perform an episiotomy, the investigators assessed
the angle of marked episiotomy lines at the first stage of labor and at the time of crowning
of the head.
Incision lines for mediolateral episiotomy were pre-marked on the perineal skin at 30°, 45°,
and 60° angles from the midline, at the first stage of labor, in women with singleton
pregnancies. The angles of the marked lines were measured again at crowning of the head.
Mediolateral episiotomy was performed only for obstetric indications.