I'm in the same boat as Granny.
Also before kids I was a scientist and computer geek and all my friends were blokes that I saw in the pub. Once ds was born I was breastfeeding from 5.30pm onwards every night for a long time and then ds was going to bed at 6.30pm but couldn't be left with a babysitter.
The bloke friends didn't like the breastfeeding at all, so I lost my entire friendship group overnight, literally. It was very difficult, but a fact of life I think.
I see them still on facebook but that's it. I now have friends who I've met at school or toddler groups, and our relationships are just as Granny says. They're basically my work colleagues now, and I enjoy knowing them very much.
If I bump into my old friends from pre-motherhood I feel almost reborn, and I love to have little catch up in the street, but I don't kid myself that I could re-enter that group. It's just not feasible.