Only in a couple cases would it be appropriate:
1. You are a child or a senior citizen and can't be responsible for yourself.
2. The wife is a medical professional who can contribute to a discussion with the doc regarding some particular medical concern you have.
Otherwise, there's no real reason for her to be there. Just tell her to relax and you'll be right back.
On a related note, is the doc a hot female? Mine is...
Makes the exam a little more interesting...
