Worried about miscarriage

I am about 6 weeks along. I have told most family and friends at this point. I told my direct supervisor but not my “big boss.” We have a holiday work party coming up this month and I will probably tell big boss in person when I see them. Part of me feels like I should wait. I don’t have my first doctor appointment until January 14, and I found out on Thanksgiving. I told my husband we’re just putting things in “cruise control” until we talk to the doctor. How long do you wait until telling your employer? The nature of my work is such that maternity leave is going to directly affect a lot of people. I don’t want to wait too long, but what if I tell people too soon and something happens? Everything feels fine I guess but I wake up every morning in fear that I’m suddenly going to lose this baby.