We were very conservative in our telling, both times. With #1, my parents and brother were the only people we told right away (didn't tell my husband's family at all, as they so cannot keep a secret). I told just a few friends around 8 weeks or so. Other family, not till after the first trimester ended. And the rest of the world (including work, school, etc.), not till after the big ultrasound and genetic testing results.
With #2, we tried the same approach. But my husband told a couple of his siblings right away, and naturally word spread through his whole family. And my mother, despite my having directly
asked her to keep quiet, pretty much told the whole freaking world as soon as she found out. I'm still really annoyed about it. Everyone else found out when you all here did, when I posted the announcement a while back
after we'd had both the u/s and the amnio results