I'm not the person you are actually asking, as I was happily childfree till almost 40, then decided to have a child, but I read the Childfree forum with a sense of fellow-feeling as I was childfree for far more of my adult life than I've been a parent, and I think my experience might be of interest.
I lost three good childfree friends (a married couple and a woman) when I told them I was pregnant. The female friend said 'Congratulations' with every appearance of sincerity and never picked up the phone when I called ever again, or replied to texts or emails.
All three were considerably older than I was, and I had assumed that their decision to be childfree had been as uncomplicated as mine had been.
Turns out I was wrong.
The friend who literally never got in touch again had desperately wanted a child long before I knew her, but her first marriage was unhappy, and her second relationship was both longdistance for years, and with a married (though separated) man who already had young adult children, at a time when divorce was illegal in his country. (We've now reconnected, twelve years on, but it's not always straightforward.)
The couple (who are the most devoted and happy married couple I know) who dropped me had also wanted children years before I knew them, had undergone a brutal form of very early IVF and had almost split over whether to adopt - she wanted to, he didn't. They never told me this. A mutual friend did, later on.
I think it taught me a lot. Many people I see talking about being childfree on here for obvious reason want it acknowledged that it's a free choice, or that having children never seemed at all appealing, or that it was a positive choice, which I get, because it was that way for me.
But the experiences of losing three friends I valued taught me that it's not always straightforward, and that even though these three people were living fulfilled and interesting lives and had come to terms with things, they still found it difficult to see someone else they considered childfree change 'categories'.