I am now five months pregnant, and have reached the point where not-especially-close acquaintances and sometimes even strangers comment on it.
At this stage of Baby Kuper Rudnick's life, when people ask if it's a boy or a girl, what they're actually asking is what its genitals are shaped like. It's funny how people who presumably understand that it would be rude to ask me what my genitals are shaped like see no problem with asking me the same thing about my unborn child. The latter strikes me as, if anything, an even more intrusive question.
Anyway, when people ask, "Do you know what you're having?", I've been trying to make a point of smiling broadly and saying, "Yeah, we're pretty sure it's a baby."