Omg, late to the post here, but I read two fanfictions where the male characters got pregnant. One was many years ago from the Star Trek: Deep Space Nine series. The Cardassian alien, Garak, got pregnant by his human lover, Dr. Bashir.

Or I dunno, maybe they were married at that point. It was written as light-hearted, humorous fic and I was curious where it would go. Ummm, the author included a blurb about Cardassian biology and how it was possible to deliver a baby through some abdominal pouch opening? Yeah, it was crazy.

For those morbidly curious, it was called "Can't Help Lovin' That Mammal O' Mine."

No explicit sex scenes, but it's implied in one scene while two other characters are conversing.

The other 'fic took place in Team Fortress 2 game universe, lol, that was another hilarious story. Soldier got pregnant and the whole team had to deal with it. But atleast this time the other parent was a female. No butt baby birth, whew! I think Medic had to perform surgery on Soldier or something.

Mpreg isn't knew, anyone remember the movie, "Junior?" I also recall in the old "Mork and Mindy" series, Mork actually laid an egg and it hatched to their full-grown son. Ummm, I guess they threw in the 'oh, he's an alien, so there' implication?

But I agree, not the best trope to use, especially if the male is human. I can see an alien or demon though, maybe even an Orc, because its possible they contain the anatomical plumbing to house a growing fetus.

The only male on Earth to give birth is the seahorse.