I don't have any genital piercings, but I think you'll probably want to hold off on the oral sex, too, or anything at all unnecessary coming into contact with it.

There are a lot of bacteria in the mouth. A warm, moist vagina can make a very good place for bacteria to grow. I do know from experience that nipple rings are not supposed to be anywhere near mouths, unwashed hands, or anything at all avoidable, really, until they've healed. By a simple extension of logic, I think the same probably holds true for hood piercings as well. I also know that you don't want to jostle a new piercing around a whole lot.

If you've gotta have oral sex, you should definitely be super cautious. Use a dental dam, or at least make sure he rinses with listerine before hand, doesn't have too much listerine left in his mouth during the oral sex (alcohol and other astringents are bad bad bad for piercings; they cause the skin to tighten, shrinking the hole, and thereby inhibiting draining, which causes irritation, infections, and can, if I remember the words of the master piercer correctly, lead to rejection of the piercing), and of course make sure you wash up very well after.

Also, check out bmezine.com for information on piercings, aftercare, experiences, etc. It's a very informative site.