What can the nurse instruct a client receiving a pudendal block about its effectiveness?

The correct choice highlights that a pudendal block can diminish the bearing-down reflex. This type of regional anesthesia is used during labor to provide pain relief in the perineal area, especially during the second stage of labor. While it effectively numbs the local region where the injection is administered, it does not eliminate all sensations in the lower body, nor does it entirely relieve perineal pain.

By reducing the sensation in the perineum, this block can also result in decreased awareness of the urge to bear down, which is vital during delivery. Therefore, option C accurately reflects a primary effect of the medication. Labor progression speed is typically not influenced by the use of a pudendal block, which means that option D would not be a valid instruction regarding its effects.