How to tell close friend who has been having fertility issues that I'm pregnant?

So there's a group of 4 of us who are all very close friends, and I've just found out that we got pregnant our first month of trying. We're having a girly evening on the 8th of Feb to catch up and have a few drinks(clearly I won't be). I was going to tell them then as I'll be 8 weeks, and we were planning a trip this year so can't plan to fly after June. They know we've been getting ready to try as I got my IUD out, and we've talked about it etc.

I already have my 2 year old son, and Diana is so so good with him. She and her fiance desperately want a baby, and they're currently investigating why it's just not happening. She left one evening from a night out after talking about a suspected miscarriage.

Essentially, I want to try and be as understanding as possible while still enjoying being pregnant with my friends. I know it can be a very sensitive issue, and how lucky we are to have this happen. So if anyone has any tips on how to not hurt her where I can help it? Things not to gush to her about, etc? I love her, and she has always been such a good friend to me I don't want to shove anything in her face without meaning to💛