The way I chose to tell my co-workers about the pregnancy was sort of cheap and hands-off. Sure, if someone were to flat out ask me if we were expecting (now), I would tell them Yes. But I chose to be more ironical and post an enlargement of the most recent ultra-sound on my office door, making people sort it out for themselves.
The effect, like our family photo gag, wasn't immediate, of course. The first problem was, when the door is completely opened, the front of it is not easily seen unless you're looking at it. Along with this problem, most of the people entering the room my office is in aren't coming into it looking for me, ha ha. I work with nurses and doctors who have much more important things on their minds (usually), or at worst, come in to grab a handful of M&Ms that have been kept in the room for ages.
It didn't take TOO long for someone to notice, and the first was a young mom who recently had her second child. I'm sure she can recognize an ultra-sound from several doors away. She only needed confirmation from me in person before being able to "spread the news." From there the news has trickled around this week and the well wishes have ensued. It's nice getting the news out instead of fibbing, and now the weekly "How's your wife doing" queries will begin. But that's okay because we are doing pretty well with it all.