[quote littlepattilou]@Trinacham
Isn't it common to tell your mum/dad/MIL/FIL first, usually earlier than everyone else though? That's what everyone around me seems to have done. I am newly pregnant and expect I'll be telling those people first, then wait for the scan for everyone else.
Nope, I disagree. As @Blossomtoes said above, don't tell ANYONE if you don't want other people you know, to know about it.
Some people, no matter how close they are to you/how well you get on; cannot keep their mouth shut. As this thread illustrates.[/quote]
I think it is common practice! We told both sets of parents and SIL when I was 9 weeks. Asked them to keep it quiet, and they did.
MIL was bursting to tell other people, but she respected our wishes and kept quiet until after the scan.
Unless they have given you reason to distrust them in the past, it's a reasonable expectation that your own parents will keep quiet. Now that OP's MIL has shown herself to be untrustworthy, I wouldn't let her in on similar information in future.
However, in the circumstances I think it is fair for OP to be annoyed.