Often, there's a plotline centered around the baby's future. Will it be a normal vampire? A hybrid with unique powers? The fanfiction might explore how Bella and the others prepare for the baby's arrival, including things like finding a safe place to give birth. And there could be a plotline about the baby being a symbol of hope or a threat, depending on different characters' perspectives.
Another theme is the idea of Bella's self - discovery. Pregnancy is a big life change, and in these fanfictions, she often discovers new aspects of herself. For example, she might find a new strength she didn't know she had, or she might face insecurities she has to overcome.
Edward is almost always there. Since he's such a central figure in Bella's life as a human and vampire in the original story, he would likely play a big role in the fanfiction too. He might be the one guiding Bella through her new vampire life.
It could be. There are many different types of fanfiction themes and pregnancy is a common plot device in some fanfic communities. However, its popularity would depend on the specific fandom it pertains to.
One common theme is the struggle with identity. Bella is no longer just human or a new vampire, but a pregnant vampire which is a whole new identity. Another theme is family. The Cullen family's reaction and support (or lack thereof in some cases) play a big role.
In vampire lore, vampires are often considered undead and not supposed to be able to reproduce in the traditional sense. However, in fanfiction, authors often bend the rules. Maybe the author has created a new kind of vampire physiology where they can reproduce. For example, they could introduce a special genetic mutation or a magical element that enables Bella to get pregnant as a vampire.
One possible storyline could be the challenges Bella and Edward face as they prepare for a new life together while dealing with the vampire - human relationship issues. Maybe they struggle to keep Bella safe during her pregnancy considering her human frailty.
In this fanfiction, it could be that Bella's second pregnancy is a complete surprise. She was not planning on having another child so soon. She then has to adjust her life plans, like her career aspirations. Meanwhile, her relationship with her partner might face some new challenges and also grow stronger as they navigate through this unexpected journey together.
Well, in addition to Bella and Emmett, there could be other characters from the original source material (assuming it's based on something like Twilight series). For example, Bella's friends might play a role, like they could be there for support or they might be shocked and have to deal with their own feelings about the situation. Emmett's family or vampire clan (if relevant) could also be important characters, as they might have their own reactions to the pregnancy.
She could also develop more compassion. Knowing she's bringing a new life into the world, she might start to see things from a different perspective, especially when it comes to the relationships within the Cullen family and their views on her pregnancy. This could lead to her trying to bridge gaps and bring the family closer together.