Perhaps a fanfic could be about a Pokémon from Ruby and Sapphire that gets lost in a different region. The Pokémon has to find its way back home while making new friends and facing challenges in the unfamiliar environment. Along the way, it could encounter different trainers and Pokémon species, and the story could show how it adapts and overcomes obstacles to return to Hoenn.
The unique character development. When a Pok mon is pregnant in a fanfic, it gives an opportunity to explore the Pok mon's personality in a new light. For example, how it copes with the physical and emotional changes. It can also show the relationship between the Pok mon and its trainer in a different way, like increased protectiveness from the trainer.
One idea could be focusing on a trainer who is trying to reunite the two legendary Pokemon of Ruby and Sapphire, Groudon and Kyogre, to stop a greater threat that emerges when their power imbalance causes natural disasters. The trainer has to travel across both Hoenn regions, facing challenges from different gym leaders who have different views on how to handle the situation.
One plot idea could be that Sapphire and Ruby are having a disagreement about how to best protect Steven. Sapphire, with her future vision, sees a potential threat approaching in a very different way than Ruby does. This leads to some tension between them as they try to figure out the best course of action for Steven's safety.
A really interesting plot for a Pokemon Ruby and Sapphire fanfiction could be set in an alternate Hoenn region. In this version, the roles of certain Pokemon types are reversed. For example, Water - type Pokemon are rare and Electric - type Pokemon are the dominant force in water - based areas. The main character could be a trainer who has to adapt to these new rules. They might have to find creative ways to battle and train their Pokemon. This could lead to some really unique and exciting adventures, as they encounter different challenges and make new friends and enemies along the way.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. These platforms have a wide variety of Pok mon fanfics, and you can use the search function to specifically look for ones related to the 'pregnant' theme. Just be sure to read the ratings and reviews to ensure the quality.
One idea could be exploring an alternate universe where the starters of Ruby and Sapphire have different evolutions. Another could be a story focused on a side character from the manga, like giving a backstory to a Gym Trainer. Maybe also a story where the legendary Pokemon Groudon and Kyogre form an unexpected alliance instead of their usual rivalry.
One idea could be exploring a new mega evolution for a less - known Pokemon in the Hoenn region. For example, making Linoone have a mega evolution with a unique design and new abilities. Another plot could revolve around a trainer who discovers a hidden, ancient Pokemon that was thought to be extinct in the Hoenn caves. This could lead to a race among different trainers and teams to either protect or capture it.
In the fanfiction, Ruby and Sapphire could be having trouble adjusting to life in a new town. Steven, who has experience with change, could introduce them to new friends and show them all the fun things about the place. Meanwhile, they could teach Steven more about their unique Gem culture, like how they fuse and their special powers. This would create a story full of cultural exchange and friendship building.
One idea could be to focus on a trainer who discovers a rare and powerful Pokemon in an unexpected part of the Hoenn region. Maybe a Pokemon that was thought to be extinct. Another could be a fanfic where the main character has to stop an evil team from misusing a powerful ancient artifact in Ruby's world. Or perhaps a story about a Pokemon trainer who befriends a Pokemon that has trouble evolving and they go on a journey to find a special way to make it evolve.
A possible plot is that a powerful villain manages to corrupt the Star Sapphire energy source. A Green Lantern discovers this and tries to stop the corruption from spreading. He teams up with a group of Star Sapphires who are also concerned about the situation. Along the way, they learn about the true nature of their powers and how they can work together more effectively to defeat the villain.