How I smiled when I read the OP and subsequent comments! You just CANNOT KNOW what it's like to be a mum for the first time. It's the hardest job in the world! TBF I think such friends are just hopelessly floundering out of their depth. I don't think as someone said, that they're necessarily 'jealous', just clueless! However, you may never have that smug 'told you so' moment when one day, in the future, somewhere, your friends as brand new parents themselves go "Eff ME! THIS is what it's all about, how can I have been such a prat?"! But you can rest assured that that day will come. Also, I believe that high-flying, ball kicking career women can actually have a harder time of new motherhood than "run-of-the-mill" gals like me. Suddenly you have a situation over which you have practically no control, no authority, nothing that can be salvaged by throwing a schedule at!
I was a late starter (36 with number 1) having spent 15 years as a health care professional and, like many of us who have experienced full time, responsible work AND motherhood, I KNOW which is easier! I smile indulgently when I hear the young women at work now announce how they can't wait to start having babies for all that lovely time off! You just can't know til you've been there.
Your friendship group will change. You'll become 'friends' with women purely because your DCs are at the same developmental stage, but then, pre kids, didn't we have 'friends' who in reality were just people who went to the same pub as us? You may well reunite with old friends once they too start sprogging (and you have every right to feel smug!), the more thoughtful of old friends may be able to maintain your friendship even though they remain childless. I have a few myself. Our friendship went onto the back burner over the first 3-4 years, but we catch up again now, but I don't expect them to go gaga over my DCs as our friendship is based on something other than the mutuality of being parents. I go to London and get hammered with them, once or twice a year instead!
Don't feel furious or betrayed by your old mates. You've moved on in your life and made certain choices, ones they may make themselves down the track. Don't waste your precious energy on worry about it!