The pudendal nerve is a nerve in the pelvic region that innervates the external genitalia of both sexes, as well as sphincters for the bladder and the rectum.
The pudendal nerve originates in the sacral plexus; it derives its fibers from the ventral rami of the second, third, and fourth sacral nerves (S2, S3, S4).
It accompanies the internal pudendal vessels upward and forward along the lateral wall of the ischiorectal fossa, being contained in a sheath of the obturator fascia termed the pudendal canal.
Difficult childbirth or bicycling[1] can compress or stretch the pudendal nerve, causing temporary loss of function, but permanent injury is rare. Entrapment of the nerve is very rare but can happen. A pelvic tumor (most notably a large sacrococcygeal teratoma), or surgery to remove the tumor, can damage this nerve permanently.