Should it be expected that when you tell someone a secret they tell their partner?!

Please read before voting!

I ask this because- when I found out we were expecting, I didn't wanna tell anyone right away because of having a miscarriage before. I wanted to wait until my first ultrasound before telling people. My fiancé wanted to tell his mom right away and I said that I don't mind as long as she keeps it a secret and doesn't even tell her BF. She told her BF and when we told her that upset us cause we specifically asked her not to tell him, she replies with "then don't tell me things I can't tell him. It's not right to ask one partner to keep secrets from their partner". My mother also used to do this to me with my step dad when they got together. I would tell her something and ask her not to tell him and by the end of the day he would be talking to me about it.

I guess I just wonder if this is something that should be expected! When a friend is telling me something in confidence and asks me not to say anything, I don't tell my fiancé. My fiancé and I don't keep secrets from each other but I feel like when it's not my secret to tell, I don't tell. Am I crazy?! Lol