I reviewed a bio today for a very successful businessman who wanted to know how to explain to potential investors in his business that he didn't have a college education.
"Don't," I said, "you've obviously done very well without it. If they want to know more they can ask when they meet you in person."
The same goes for any one of a number of potentially 'sensitive' subjects - time out of the work force to raise a family is another good example, or to recover from an injury or illness. You can certainly mention it, but don't feel the need to justify or explain it. Don't induce doubt that might not otherwise be there.
Focus and concentrate on what you have done or can do when writing your bio, that's what counts.
Jill Townsend is the author of "How to Write a Great Bio", an e-book with tips on writing a good bio fast, and with confidence.