When is everyone announcing?

Jennifer • Baby Keir Samuel Thomson was born on 3/12/17 @ 40wks and 4 days after 23 hours of a tough labour which did not go to plan. However he is here now safe and that’s all that matters very proud mummy and daddy.
I'm 12 weeks today with 2nd pregnancy. I have my 12 week scan tomorrow so will get a more accurate due date then. My 1st pregnancy ended in mc 2 years ago at 8weeks and 6days, I literally told my friends and family the day before so it was heart breaking having to explain to everyone what had happened. This time I'm reluctant to tell people even family until 16 weeks minimum. 
Yesterday my SO had a call from his brother to say his partner was 7 and a half weeks pregnant and now my SO is desperate to share our news with the world.
So I'm curious when do people usually announce their pregnancies?