So just a bit of back story (not to bore anyone)...
My fiance and I have known each other since we were little and our moms are best fiends
My mom found out about my pregnancy fetish (I guess you could call it) when I was younger. Since my fiance's mom tells her everything she told her (before we were dating). So needless to say she has known about it for a long time.

So fast forward to tonight and we were hanging out with her two sisters. She flat out tells them about that. They didn't say anything about and didn't look at me weird. The topic of convo was about masturbating and other things. So, I guess that's a good thing? I don't think she knows it's still there, but who knows. Maybe something might creep in when she does get pregnant down the road. I know she wants a lot of kids (hey I have no problem with that.) So who knows... I guess I don't gotta hide it no more?

Any thoughts?

Well, I wouldn't worry about it. Especially considering she's known for years and still agreed to marry you. IF anything, she might be open to engaging with the fetish with you. What is kind of weird(well, to me at least) is that she and her sisters were discussing masturbation while you were there.

Yes we do call it a pregnancy fetish or I often call it a pregnant fetish. We desire to have sexual relations with a certain person who is pregnant and we worship them like a goddess.

Well it was only a matter of time of when your mom would find out about your pregnancy fetish. It's weird that the mom of your fiancé's would be told about your fetish. It'd even more weird IMO that your fiancé found out before being your fiancé and being your girlfriend.

I find it surprising that your fiancé told her sisters flat out in front of you and not behind your back. Or even when you guys are married and you knocked her up and she sees clues of your fetish. That's the major curve-ball right there on that night. [We'll find out down the line if she is really ok with your fetish when she's pregnant. That for you is a golden opportunity for you to live up to your sexual desire]

I think it's a bit messed up that she just blurted it out without asking you first. One of my friends that I told about my fetish in confidence apparently later told her entire college friendgroup, and I was really upset about that! Thankfully, they were all understanding, but still, I think that when someone has a secret that's clearly very important to them, you should ask them before telling anyone else.