Well, the simple solution is click on the recommended "sharing" game links, and see if it has the pregnancy tag...
However, this is a tough one... What context are we talking??
I've played a bunch, and I cannot think of one "sharing" story where "visible pregnancy" is "involved".
If it is in a story, it's typically been in an ending.
And those endings are usually on the NTR, Harem, or solo girl paths.
And I don't recall any so far where it's the "other guy's" kid or anything...
I think I recall visible pregnancy in the endings of Jealousy (Captain Kitty spoiler list)... but it's been a while since I played that one, and pretty sure it was in the "harem" or solo girl endings... The girlfriend with the strap-on isn't going to knock anyone up...
I think A Happy Marriage had it in one of the endings...again, it's been a while, and don't think it was involved with the "shared" but on the her leaving endings... but game has no pregnancy tag, so I could be mixing it up with another story...
Dirty Texts ends with a pregnancy test...lol, no visible...
Dang, this has me stumped...
I know of several games with visible pregnancy, particularly in the endings, but they aren't "sharing" games...
Add: Oh, Pineapple Express (Dimajio spoiler list) has a pregnancy ending... maybe it's the other dude's, maybe it isn't...
Another from same dev, Make Me Happy, might be what you're looking for, too...
And Lost in Paradise... think it has an ending or two along the pregnancy lines. I think it's on the "bull" route though. I don't recall if the "cuck" route had it...