First up, there's the "Pregnant with Puppies" series, which (while plentiful of content) doesn't really do it for me. Puppies seem like kind of a cop-out (and a common one).http://www.asstr.org/~Kristen/10/pregpups.txthttp://www.asstr.org/~Kristen/39/pregpup3.txthttp://www.asstr.org/~Kristen/39/pregpup4.txthttp://www.asstr.org/~Kristen/39/pregpup5.txt
I don't know if that's all of them, navigating asstr.org is kind of hellish (I just use Google to find what I'm looking for on it).
Here's one that's not great (I guess I can't think of any off the top of my head that really suit my tastes very well). It's a brief and shallow interview with a girl who was impregnated by a blue whale (but there's not much pregnancy content and it kind of rubs me the wrong way).http://www.asstr.org/~Kristen/63/abluewhale.txt
WARNING: These aren't really about pregnancy, but extreme insertion and some sort of fetish that involves… stretching vaginas until they're useless? I don't even know. ANYWAY, there's scat and underage stuff and a lot of vaginal prolapse, but if you can look past, there's horse pregnancy and elephant pregnancy and even one woman giving birth into a girl, so… yeah. But again, be warned. http://www.asstr.org/files/Authors/AnnaliseLenai/Trista's%20Adventure/Trista's%20Extreme%20Adventure%20Part%201.txthttp://www.asstr.org/files/Authors/AnnaliseLenai/Trista's%20Adventure/Trista's%20Extreme%20Adventure%20Part%202.txthttp://www.asstr.org/files/Authors/AnnaliseLenai/Family%20Expansion/Family%20Expansion.txt
If I remember more later, I'll post them.