How to announce your pregnancy to colleagues?

Silly question but I'm really awkward haha don't know how to tell people about my pregnancy 😝. I'm 13 weeks pregnant, already told my bosses but no idea how to tell my colleagues! I have a close group of colleagues and we meet up often but I feel it's so awkward to just say I'm pregnant out of the blue. I want to let them know first before announcing widely on Facebook etc. But how? Do you send mass message to the group, or just tell each person privately? How formal do you make it? Help pls!