I think that people think they're being friendly and don't realize the impact that their questions have.
I have three adopted children. The birthmother of my oldest, when she was pregnant with him, used to get tired of all the strangers who would come up to her and ask, "When are you having the baby? Is it going to be a boy or a girl? What are you going to name him/her?"
Finally, she started answering back, "Baby? What baby?"
That shut them up.
Or she just could have said, "Oh no, I'm not pregnant, that's just a tumor. Big fella,ain't he? Up to 20 pounds. We call it George. People rub it for luck, go ahead..."
Back up one month. When people ask when the baby is due, ...this is July. Say June. You can see them counting in their heads. And re-counting with a puzzled look. Just smile and walk away.