I was a little embarrassed. It was also the first incident of pregnant-belly-touching - though at that time I could still (with effort) button my low-rise jeans so the belly wasn't much.
It happened again today back at work. A lovely lady whom I like very much was chatting with me about our trip, and at the end she remarked I hadn't gained weight, despite going on and on about how great the food was. "Yes," I replied, "as I was telling you, we walked so much every day!" D'oh! That did me in. Her suspicions confirmed, she gestured at my stomach. "Are you...?" Yikes! My days of keeping it on the DL are clearly numbered. (This is one reason it's a secret.)
I saw my dad and sister two days ago, as far as I know they don't know. Also, I work with very few moms. All the women that most frequently interact with me do not have kids, so I think they will lack the eagle eye of moms-who-aren't-having-more-kids.
That being said, I know the next time I see my MIL, it's all over there.