How soon are you / did you tell family?

Mrs E in Oregon

We want to wait until 12 weeks or until I'm showing. I am going to tell my boss in the next few weeks if I start getting to tired during work. BUT, my mother-in-law is the person you tell a secret to when you want the whole world to know your business. We might as well post it on FB if we tell her anything.

 So when did you tell and why? Or when will you tell and why?