A plot could focus on the relationship between Bellatrix and the father of the child. If it's a fellow Death Eater, how does their dynamic change? Do they become more protective of each other? Or perhaps the father is an unexpected character, like a wizard who was undercover among the Death Eaters. This would add a whole new layer of mystery and drama to the fanfiction.
The fanfiction could also explore Bellatrix's pregnancy in the context of her own past. Maybe she has a difficult pregnancy that makes her reflect on her own upbringing and family. She could be haunted by memories of her own mother or family members, and this could influence how she prepares to be a mother herself.
One idea could be exploring how Bellatrix's pregnancy affects her loyalty to Voldemort. Maybe she starts to question some of his more extreme actions as she thinks about the future for her unborn child.
One possibility could be Rodolphus Lestrange, her husband in the wizarding world. It would be a traditional choice and could explore how their relationship evolves during the pregnancy. Another option could be Voldemort himself. It would be a very dark and twisted scenario, but it would add a lot of drama to the story.
One interesting fanfiction could be about Bellatrix's early years at Hogwarts. It might explore her friendship or rivalry with other Slytherins. Another could be a story where Bellatrix has a change of heart after a magical encounter and tries to redeem herself. And there could also be a fanfic that focuses on her relationship with Voldemort in a more in - depth way, showing the power dynamics and her unwavering loyalty.
One interesting fanfiction could be about Bellatrix's early years at Hogwarts and her first encounter with a young Harry Potter in a magically altered scenario. It might explore how their paths could have crossed in a different way than in the original books.
It could be Voldemort himself. Given her extreme loyalty to him, it's not a far - fetched idea that there could be some sort of connection between them that led to her pregnancy.
One great Bellatrix Lestrange fanfiction is 'The Redemption of Bellatrix' which explores an alternate universe where she tries to break free from Voldemort's control. It delves deep into her character, showing her internal struggles.
One interesting fanfiction could be where Bellatrix has a change of heart due to some magical accident and ends up helping Harry Potter secretly. In this type of story, there could be a lot of internal conflict for Bellatrix as she battles her loyalty to Voldemort and her newfound sense of morality. Another might be a time - travel fanfic where Harry goes back in time and has to deal with a younger Bellatrix, trying to prevent her from becoming the dark witch she is in the original timeline. There are also fanfictions that explore a more complex relationship between them, perhaps a forbidden friendship that develops against all odds.
Perhaps a plotline where Harry discovers the truth about his parentage later in life. He has been raised believing Bellatrix is his mother, but then uncovers evidence that it's all a complex web of dark magic and deception. This could lead to a journey of self - discovery as he tries to figure out who he really is and where he belongs in the wizarding world, all while dealing with the stigma of being associated with Bellatrix Lestrange.
A really interesting plot could be Bellatrix being given a chance at redemption. In this fanfiction, she could start to question Voldemort's motives after seeing the destruction he causes. She might then try to secretly help the Order of the Phoenix. Also, a plot about her teaching a young Death Eater the ways of the Dark Arts and having second thoughts about it mid - way through could be fascinating.
Some fanfics explore Bellatrix's family relationships more deeply. Like her relationship with Narcissa. There could be a plot where Bellatrix has to choose between loyalty to Voldemort and protecting her sister, which adds a lot of emotional depth.