Well, obviously Bella herself. Then there could be the father of the baby, if it's not a mystery. There might also be her friends or family members. They could play different roles, like being supportive or having doubts about the situation. And perhaps there are some medical characters, like a doctor or a healer if it's in a more fantasy - based setting, who are involved in taking care of her during the pregnancy.
Definitely Bella. There could be a love interest who is either the father or someone who has a complex relationship with her during this time. Her parents or guardians, if they exist in the fanfic's world, would likely be involved too. There may also be other hybrids who can relate to her situation and offer their support or advice. And let's not forget any sort of authority figures in the fanfic's setting, like a tribal chief or a council member if it's a more unique world - building scenario, who might have an opinion on her pregnancy.
Bella is the central character, of course. If this is in a world where there are different species, there could be representatives from each of the species that her hybrid nature is composed of. They might be interested in the pregnancy for different reasons. Maybe there's a mentor figure who has experience with hybrid pregnancies and can guide Bella. Also, antagonists could be involved. They could see Bella's pregnancy as a threat to their own beliefs or power, and try to interfere.
Also, any friends that Renesmee has made throughout her life could be involved. They might be there to offer moral support, or there could be some who are jealous or envious of her situation, which could add some drama to the fanfic.
Another character that could be involved is Charlie, Bella's father. His reaction to his daughter being pregnant in the strange world of Eclipse could be a significant part of the story. He might be confused, worried, or try to protect Bella in his own way. Also, some of the werewolf pack members aside from Jacob could also make appearances and contribute to the story based on their relationships with the vampires and Bella.
Tatsumi is very likely to be involved as he has a significant relationship with Esdeath in the original story. Her subordinates in the Jaegers might also be part of the fanfic. They could be shown as being protective or having mixed feelings about her pregnancy.
Her partner would be a very likely character to be involved. They could be the source of support, or in some cases, the source of conflict if they have different views on the pregnancy. Her best friends are also likely to be in the fanfic. They might be there to throw baby showers, give advice, or just be a shoulder to cry on.
Obviously, Cameron herself is the central character as she is the one who is pregnant. House is likely to be involved as he is her boss and has a complex relationship with her. Chase, her former love interest, would also play a significant role. Wilson, as House's friend, might also be part of the story, perhaps providing some advice or just being a sounding board for Cameron.
One common theme could be the challenges Bella faces as a pregnant hybrid. For example, she might struggle with her identity, being part of two different species. Another theme could be the reactions of the other characters in the fanfic. They could be supportive, or there could be conflict due to her unique situation. Also, the fanfic might explore how she prepares for the arrival of the baby, like creating a safe place in a world that may not be fully accepting of hybrids.
Well, obviously Juvia herself is the central character. Her partner would also be very involved. If it's in the context of Fairy Tail, Gray would likely be her partner in the fanfiction, as they have a strong relationship in the original series. Then there are their friends like Lucy, Natsu, and Erza. They would probably be there to support Juvia during her pregnancy, offer advice, or just be there for the big moments.
Obviously, Octavia herself is the central character. Her brother Bellamy is likely to be involved. He would probably be very protective of her and the unborn child. Clarke might also be part of the story, perhaps providing medical knowledge or just being a friend to Octavia during this time.
The Cullens are very likely to be involved. Edward, of course, would have a huge role as Bella's former love interest. Carlisle, with his knowledge and experience as a vampire, could help Bella adjust to her new life. Alice might use her precognitive abilities to foresee any problems Bella could face. Also, Jacob could be in the story. His reaction to Bella becoming a vampire would be interesting, considering his past relationship with her and his werewolf nature.
Obviously Lana herself is the central character. Her Pokemon partners are very likely to be involved. For example, Popplio might be constantly by her side, providing emotional support. Ash and his Pikachu could also be part of the story. Ash, being a good friend, would probably offer his help and advice. Misty might also be there, sharing her own experiences or just being a good friend to Lana during this time. Brock could be involved too, perhaps using his knowledge of Pokemon and nature to ensure Lana has a healthy pregnancy. And other trainers from the Pokemon world who are friends with Lana might make appearances to show their support and be part of the story.