I had a roommate say something to a like 9 month pregnant skinny lady on the beach once, she was showing off the belly, but she responded something like, "I'm not pregnant".

I've seen some women that kinda looked like they had a mid pregnancy belly, but they were way too old, so I never ask, unless there are other things indicating it as well, like the very clear belly rubbing and smiling, and more.

I only had one person ask while I was actually pregnant, then there were a few who had seen me before, and the saw me when I was like 8-9 month alone, so it was very clear! Never had it outside of that though. Doesn't sound fun at all!

One if my young nieces asked once, and she it would be fun if we had a baby. We had just found out I was pregnant with our son a few days before that, but since we lost one the year before, we didn't disclose of our news at that time.