I have to echo what embre said. In the US, physicians are "mandatory reporters." If they suspect abuse, they're bound by law to report it. It's far better to sit down with your doc and be absolutely up front about your activities, stressing that they're completely consentual. It's NOT the easiest conversation to have, but it's a very good thing in many ways. The other side of this is, what happens if your doc doesn't know, and you avoid what may be necessary health care for fear of embarassment? I've had one friend put off a mammogram because of piercings, who finally got scanned only to find an early-stage tumor. Please don't delay caring for yourself in this way.

For the record, I'm pierced, too...Nipples, clit hood, and outer labia. I recently had to go for an MRI of my left knee. Oh my the chuckles the receptionist and I had, when I had to ask about my piercings. Nobody could come up with a satisfactory answer, so I took them all out for the exam and put them back in right away. No problem, except Master had wayyyyy to much fun resetting my hood ring.