I had a man (I had never met) tell me at a Christmas party - "Oh, you must be due on the Dec 25th." No - actually I'm not, I have a ways to go. Then he responded back with, "Oh no, you will go on the 25th."
The best was earlier this month though - a young looking woman (maybe 18?) came up to me at Kohl's:
Her: Ooohhhh, when are you due?
Her: Ohhh (in a sad voice) you are so much bigger than I was.
Me: You know that's rude to say to me,...