I would just start talking in vivid colour about everything TTC, pg, and giving birth related. Ask him if he's ready for that? If he's not, keep it in his pants!
Agreed. Pick up your phone and pretend to be talking to a friend who is TTC. Start asking "her" about her CM's color, consistancy, etc. If he makes any comments, just say "Oh, I thought that we could talk about our very personal things at work since you seem to have no problem doing that."