Hey there. Been there. Trying to have kids and having no success is awful, and I am so so sorry. It's indescribable pain that you have to mask everyday at work and it just grinds you down.
Sadly, parents freely expressing themselves is unavoidable wherever we go. The best you can do is politely excuse yourself from the conversation—and you don't owe anyone an explanation either. Nothing wrong with setting up boundaries for yourself. But you have to do it; you cannot control the behavior of people around you. And frankly, parents are human, too. They may say, "oh my spouse/kids are driving me crazy!" but who knows, that could be a cover story for some other deep-rooted problem or pain that they are not quite ready to deal with and/or share openly.
If you haven't already, find a support group, a therapist, trusted friends, etc. outside of work. Be kind to yourself. And remember, it WILL get better over time, no matter how the future plays out.