Yes, there might be such fanfictions out there. Fanfiction often explores alternative storylines. However, this goes against the original 'Twilight' series canon which pairs Bella with Edward and has different family relationships.
This kind of fanfiction concept is really out - of - the - box. If Bella is pregnant with Aro's baby, it might introduce a new power or a new type of vampire - human hybrid. The story could focus on the pregnancy itself, like how Bella copes with the physical and emotional changes. It could also show how the baby might grow up in a world full of vampires and werewolves, and what kind of impact it would have on the existing power balance in that fictional universe.
One possibility is that there would be a huge rift between Bella and the Cullens. Since Edward was her previous love interest, this new situation would be extremely difficult for them to accept. And it would also make the Cullens' relationship with the Volturi even more complex.
Bella would likely become more protective and maternal. She might also grow in strength as she faces the challenges of carrying a baby in a rather complex situation. Klaus would probably become more responsible. His focus could shift from his usual self - centered pursuits to ensuring the safety and well - being of Bella and the baby.
Well, one possible plot development could be the internal struggle of Bella. She might be conflicted between her feelings for Klaus and the implications of having his baby. For example, she could worry about how the baby will fit into her existing life or the reactions of those around her. Another aspect could be Klaus's reaction. He might be overjoyed and protective, or he could be hesitant due to his complex nature and the many enemies he has. There could also be a plotline where they face external threats because of the baby, like other supernatural beings who either want to harm or use the baby for their own purposes.
Well, they would become even closer as they are about to be parents. Edward would be extremely protective of Bella, not just because she's his love but also because she's carrying their child.
One possible plot could be that Bella and Jacob initially struggle with the situation. Jacob might be overjoyed but also worried about how others, especially the werewolf pack, will react. Bella could be conflicted as she has a complex past with Edward. They may face challenges from different factions in their supernatural world, but ultimately decide to face everything together for the sake of their unborn child.
One interesting plot development could be the reactions of the Cullen family. They might be overjoyed at the prospect of a new addition, but also worried about the potential risks involved since Bella is human. Edward would likely be extremely protective, perhaps even more so than before.