I believe I have one working example of this, but alluding to it would be a massive spoiler.
Perhaps send me a private message, if you are interested, and I will disclose what I'm thinking of. It is story-related though, as it is used as a cliff-hanger mechanism more than anything - a hint at a potential sequel most likely.
I am assuming you are meaning instances where the story remarks on the pregnancy, as in it is something that exists within the story, rather than a collection of actors who have been pregnant whilst on camera, but the character they are playing is not actually pregnant in the story. These would be a lot more common.
I'm thinking what your after is going to be pretty hard to find. Perhaps a side character in a romantic comedy?