I've heard a few success stories of how people have managed to find pregnant girls on Tinder, so I thought I'd download the app. Well, I've been swiping left for two days now and have yet to find anyone that's pregnant. (Although there are a ton of girls displaying glorious amounts of cleavage.)
Am I barking up the wrong tree here, or should I keep persevering?

I think you're barking up the wrong tree. I've seen screenshots of pregnant girls on Tinder but I've been using it since January and I haven't seen a single pregnant girl (of course, maybe some of them are pregnant but their profile pictures didn't say so or they didn't tell me, but still, pretty low chance). I'd look on dating websites where you can specify that you're looking for pregnant girls. Tinder is completely random.

Yeah, i took me a year until I found the preggo I'm talking to on tinder. Good thing I'm attracted to both pregnant and non pregnant females

Really depends on where you are. In a rural area, half the girls you're talking to may have kids already (and my college is so small that over 80% of the girls on it are townies).

Yeah, there's no shortage of girls with kids on there. Lol. It's just finding a still pregnant one that's the problem.