An 'fma oc fanfic' is a fan - created story related to 'Fullmetal Alchemist' (FMA) with an original character (OC). It could be about the adventures of this new character in the FMA universe, their interactions with the existing characters like Edward and Alphonse, or how they might change the course of the story's events.
When starting an 'fma oc fanfic', you need to immerse yourself in the FMA lore. Know about the history of Amestris, the role of the State Alchemists, and the concept of equivalent exchange. For creating your OC, think about what makes them unique. Maybe they have a special alchemy ability that's different from what we've seen in the original. You can then start building your story around how this OC's presence disrupts or enhances the existing storylines in the FMA world. It could be as simple as starting with a description of your OC's daily life in a small town in Amestris and then gradually introducing the bigger elements of the FMA plot.
A common theme is the OC having a unique alchemical ability that sets them apart. This can lead to various storylines such as being hunted by the military for their power or using it to save others. Also, the theme of redemption can be present, where an OC with a troubled past tries to make amends through their actions in the FMA world.
I'm not sure specifically if there is a publicly available 'fma riza pregnant fanfic'. You could try searching on some fanfiction websites like Archive of Our Own or FanFiction.net.
First, study the world of Fullmetal Alchemist. Know the rules of alchemy, the different factions, and the overall tone. For example, if your OC is an alchemist, make sure their abilities are within the realm of what's possible in the FMA world. Second, give them a backstory that makes sense. Maybe they had a mentor who taught them alchemy, or they come from a family affected by the Ishvalan War.
To write a good fma crossover fanfic, start by choosing the right crossover. It should be something that has potential for interesting interactions. For instance, if it's an FMA and Bleach crossover, think about how alchemy and soul reaper powers could interact. Research both fandoms thoroughly. Look at their cultures, technologies, and power systems. When writing the story, focus on the emotions of the characters. Show how they react to this new and strange crossover world. Use vivid descriptions to bring both universes to life in the fanfic. And don't forget to proofread and get feedback from other fans.
The unique alchemy system in FMA can be incorporated into a family portrait fanfic. For example, the transmutation circles could be related to the family bond, like a special transmutation circle that represents the family. This would be different from other fanfics.
It could be about the Elric brothers and their family. Maybe it shows a different take on their family before the tragedy. For example, it could focus on their daily life, with Hohenheim being a part of it, and how they interacted as a family. It might also include their mother's influence on them.
One possible plot could be that Riza discovers she's pregnant during a time of relative peace in Amestris. She then has to deal with the reactions of her comrades, especially Roy Mustang, who might be both overjoyed and worried about the implications for their future.
A really interesting fma crossover fanfic idea might be with the world of Fullmetal Alchemist and the Lord of the Rings. Imagine the Elric brothers in Middle - earth, facing the challenges there. They could use their alchemy skills in a world filled with magic, elves, and orcs. It would be a very unique combination as the concepts of alchemy and the magic in Middle - earth are quite different.