For operative vaginal delivery, what is the level of sensory block needed to cover pain?

Vaginal delivery :The first stage of labor requires a sensory block to the level of the umbilicus . During the second stage of labor and for operative vaginal delivery, a sensory block of S2 through S4 is usually adequate to cover pain from perineal stretching and/or instrumentation. (Ref: William's Obstetrics; 25th edition)