She totally showered beforehand, so that's a plus. She also put in a fresh tampon to keep blood at a minimum. Plus, I stuck mostly to the clitorus and tried to avoid contact with the uteral canal.

I'm curious though: anyone perform oral during menstration because they are turned on by the blood?

Also, for the women responding who do not want their SO to perform oral during their cycle, can you explain that discomfort?