My MIL is pretty good. On my previous pregnancy we decided to tell my mum (who lives overseas) and my MIL (to keep it fair) when we found out. As soon as we told her she *had* to tell FIL and SIL (fair enough but I had not told my brothers or dad - we agreed to it at the time). After my first scan she took it upon herself to tell people. I was barely 6 weeks pregnant. DH called and told her to stop telling people. We had to tell the people who were told to zip it as noone in my family knew. And then we get an angry call from SIL that we made her cry.
And what about my tears? And that I was upset that I couldn't tell people my news?? Did not matter.
What made it worse is our NT results were not good (for T13/18 ) and I really did not want to say anything until we had results but we had to due to the news spreading already *sigh*.
So this pregnancy we have not told anyone. And we will make sure WE tell people.