My mother cannot keep a secret, no matter how much I impress upon her the necessity.
The most recent situation came when I sent her an e-mail thanking her for something and letting her know I was seven weeks pregnant. Remembering who she was, I quickly sent a follow-up e-mail begging her not to tell people. Within hours, I received a congratulatory text from my sister-in-law.
I sent my mother an e-mail illustrating exactly why I found this upsetting. She apologized profusely and promised never to do it again. Then last night, she accidentally included me in an e-mail to my cousin: "Don't tell her I told you. I got told off for shouting it out to other family members."
Talking to her firmly but nicely doesn't work. My husband says, "Never tell her anything ever again that you don't want everyone to know," which is a painful thing - it makes me sad that I can't share things with my own mother.
Answer: We don't get to design people to our specifications, even when we feel justified in requesting a change, even when both parties would arguably benefit from it. The fact remains that you don't have final say in what she says. Never will.
So: Never tell her anything ever again that you don't want everyone to know.
While your husband is correct, you're not correct in interpreting it to mean only that you "can't share things with my own mother." You can share your news knowing she's going to broadcast it.
View your mom from now on as a binary choice: "Which is more valuable to me right now, telling Mom, or my privacy?" When you can't have both, you choose the one you want more.