Hi! 

Hope you are ok, I have a question...
How did you express to your partner that you have this fetish? 
Or what was your reaction when they talk you you? 

I need some tips to approach this with my partner.

One important bit of information here is that you're female, so that can change the dynamic a little from what the vast majority of us here (as guys) are familiar with.

Whenever I'm getting to know someone new these days, I just say it very matter-of-factly. If we're talking sex and kinks and whatever, I throw out there "I have two main kinks, if you wanna hear 'em. They're not that amazing or anything." And of course, everyone does want to know. I share the other one first because it's basically just an overfascination with boobs, and then "and I think pregnant women are hot. Like really hot." And that's usually as far as it goes. A lot of people don't really press for more information. In this way, I make sure that everything's already out in the open for anyone who could become a partner.

I haven't had a situation where someone was already a partner and then I had to reveal my kinks to them. I suppose that could complicate things. I would definitely be shy and afraid it could mess things up, but I think it's important to stay strong against that because if you're going to get judged and dumped for your innocent kinks, then the dumper is too closed-minded to be a good partner, anyway. In other words, use logic to talk yourself out of being afraid to share.

My suggestion, without knowing much else, is to bring it up in conversation as naturally as possible, rather than a "honey, sit down, I have something I need to tell you" kind of approach. Be talking about sex and fun stuff already. Ask what they like. Then offer up what you like, without making it into a big deal (because making it into a big deal will make it really difficult for you to actually get the words out). It's OK if you have trouble finally just fucking saying it -- if you feel something holding you back. It can be really hard to tell someone that you already like and want things to go well with. But if you're comfortable with them, you'll be able to say it, and it's a relief.

One last note is that as a woman, you might have to clarify that you're not asking to have a baby with your partner right now if you're worried that could scare them off or something. ...unless um, you do want that, in which case get yo preggo on, girl!