Perhaps the OC discovers she is pregnant just as Itachi is about to embark on a very dangerous mission. She has to decide whether to tell him or not. If she does, Itachi might be conflicted between his loyalty to his mission and his love for the OC and the unborn child. This could lead to a lot of internal struggle for him and also create a tense situation between the two characters.
One plot idea could be that the OC is initially scared to tell Itachi about the pregnancy. She might worry about how it will affect his mission or his standing in the ninja world. Another could be that Itachi, being the protective type, goes to great lengths to keep the OC and the unborn child safe from his enemies. He might even consider leaving his organization to ensure their safety.
One plot idea could be the OC struggling with the idea of being a mother at a young age while Sasuke is away on a mission. She has to deal with the judgment of the village and her own insecurities. Another could be Sasuke's reaction when he finds out. He might be initially shocked but then become very protective.
One plot idea could be the challenges she faces in hiding her pregnancy from certain characters in the fanfic's world. Maybe there are those who would use it against her or the group she's associated with.
A possible plot is that the OC discovers she's pregnant at a very inconvenient time, like right before a big mission. She has to decide whether to tell Bucky immediately or wait until after. This could lead to a lot of internal conflict for her. And then, as the pregnancy progresses, Bucky could start to become overprotective, which might cause some friction between them as the OC still wants to maintain her independence.
Well, a plot could revolve around Naruto being in a situation where he has to keep a big secret from his friends, just like Itachi did. This could create a lot of internal conflict for Naruto. He might start to isolate himself, which his friends would find strange. Also, in terms of power, Naruto could be exposed to a power similar to Itachi's Mangekyo Sharingan. He would have to learn to control it without losing himself, and this could be a great arc in the fanfiction. It would show Naruto's growth as he struggles with the new power and the implications of using it.
Maybe Itachi is on a secret mission outside of Konoha and he saves Naruto from a group of rogue ninjas. Naruto, being Naruto, is immediately drawn to Itachi's strength and kindness. They start to train together in secret. As they train, Naruto discovers Itachi's past and the burden he carries. This leads to Naruto vowing to help Itachi find a way to clear his name in Konoha and they become close friends in the process.
One idea could be exploring how Yennefer deals with the physical and emotional changes during pregnancy while still being a powerful sorceress. Maybe she has to find a way to protect her unborn child from the many enemies she has made.
One idea could be exploring how she and her partner (like Percy) adjust to the news. They might have to deal with the reactions of their friends and family. Another could be the challenges she faces during the pregnancy, like her still wanting to be involved in heroic adventures but having to be more cautious.
One idea could be exploring how Gwen's friends and family react to the news. Some might be overjoyed while others could be worried. Another plot could involve Gwen dealing with the physical and emotional changes during pregnancy while also trying to maintain her normal life, like her hobbies or job. And a third could be about the father's role, if known, and how their relationship evolves during this time.
A plot could revolve around Kushina having premonitions about the future of her unborn child during her pregnancy. She might have dreams that she tries to interpret, and this could add an element of mystery. Also, it could be interesting to see how her pregnancy affects her ninja duties, if she has to take a break or if she finds new ways to contribute while pregnant.
One idea could be exploring how Kairi's friends react to the news. For example, Sora might be initially shocked but then become extremely protective. Another plot could revolve around Kairi preparing for motherhood while still dealing with the challenges in her world. Maybe she has to find a safe place to raise her child away from the ongoing battles.