I'm not in touch really at all with either my postnatal group from DS1 or my antenatal group from DS2. I think a couple might still be FB friends from the second group. Neither group was in my area.
However, I am in touch (mostly FB) with the two women who organised local coffee mornings in my area when my kids were babies. The first has moved to the Midlands. The other still lives locally, and she and I were both involved in setting up a breakaway NCT branch after DS2 was born, because the boroughwide branch mostly organised activities in the west of the borough and didn't come to our (much less affluent) area much. I wasn't sure about starting a new branch when the idea was first mooted, and was convinced, most, by the antipathy and outright nastiness/snobbery (and possibly some racism towards one of our group). Worst, a lot of the nastiness came from two NCT postnatal tutors, including the one who had run my course, and I felt that was very unprofessional and disappointing - it seemed to bring out a side to her I'd not seen before and wished I hadn't.
I had gone back to work by the time we set our own branch up so I mostly saw people at some of the initial meetings or through the book group we had for a couple of years after that.
DS2 is nearly 15 and we set up our breakaway over 14 years ago. I've lost touch with some people, and quite a lot of people have moved out of London, including women who returned to Ireland and Australia. Very sadly, one of our founding members lost her daughter aged 12, and one woman who I met through NCT was perhaps most in touch with still out of the group died. Though I don't meet up with others, I do have some contact with a few on FB or run into those who still live locally occasionally. And occasionally I've met someone through something unrelated who has benefited from our efforts to set up a more local group - I believe it's still going.