A couple of instances recently.
I went for a leg wax (I cannot do them myself and hate shaving) and it wasn't my usual beautician (I think the usual one knows we have adopted, but she is more restrained in her comments too). I mentioned that Mr Spouse was looking after the baby, and the beautician asked me a few other questions and then asked "so, how was the birth". I could not think what to say so I said "I don't really want to talk about it". I think she was also going to ask "so, how old are you?" but I deflected her with another question.
None of my mummy friends have asked me that outright (or even my age!). When the topic comes round to birth horrors, I just play with the baby or change the subject.
Yesterday I had lunch with a very good, very old friend who was one of our referees for Baby Spouse's home state (they require non-relative referees while all the other bodies require one to be a relative). She was talking to another friend about people called Somethingson* which is her husband/kids' surname, and a family name in that friend's family. It's a fairly common name but the friend was keen to research families with that name. "Of course, D's father isn't a real Somethingson because he was adopted".
Speechless. As usual you think what you should have said later - it's not worth saying to her now but I wanted to say "but Baby Spouse is a real Spouse".
*names changed to protect those not present