The plot might twist when it's revealed that the pregnancy is not a normal one. For example, the baby could have some extraordinary powers from the start. Since Sakura has her own medical and chakra - related abilities and Madara was extremely powerful, their child could be born with abilities that are unheard of. This could lead to many in the shinobi world either fearing or trying to use the baby for their own gain.
One possible plot twist could be that the pregnancy is a result of some sort of ancient jutsu gone wrong. Maybe a forbidden technique that was meant to save Madara's life but instead had the side effect of causing Sakura to become pregnant. Another could be that an enemy has somehow manipulated their DNA to create the pregnancy as part of a grand scheme to control the two powerful shinobi.
One possible plot twist could be that Sakura discovers a hidden weakness of Madara's during the fight. Maybe it's a chakra point that, when struck, temporarily paralyzes him, giving her an upper hand.
One possible plot could be that they are in a world where enemies have become allies. Madara, with his powerful abilities, and Sakura, with her medical skills and strength, find themselves in a situation where they accidentally get closer and Sakura becomes pregnant. This could lead to a story of them trying to protect their unborn child from various threats in the shinobi world while also dealing with the shock and change in their relationship.
Another plot twist could be that Madara is being controlled by an even greater force when he captures Sakura. And Sakura realizes this and has to find a way to break the control on Madara while also escaping from him. This would completely change the direction of the story and introduce new challenges and opportunities for Sakura to show her strength and intelligence.
One possible plot twist could be that right before the wedding, Naruto has to go on a dangerous mission. This could put their relationship to the test as Sakura has to deal with the fear of losing him. She might even consider calling off the wedding. Another plot twist could be that an old enemy resurfaces and tries to use Sakura as a leverage against Naruto, forcing him to make a difficult choice between his love and the safety of the village.
One possible plot twist could be that the pregnancy is not a normal one. Maybe there are some special powers or abilities that the baby inherits which causes all kinds of chaos and challenges. For example, the baby could have the power to manipulate time like Alice, but it's out of control in the womb and affects the flow of time around them.
One possible plot twist could be that the pregnancy is unexpected and it forces Luffy and Nami to reevaluate their relationship within the Straw Hat crew. For example, they might have to deal with how their crewmates react, especially those who are protective of Nami like Sanji. Another twist could be that there's some sort of magic or mystery involved in the pregnancy that endangers Nami and the baby, leading Luffy on a quest to find a cure or solution. It could also be that the pregnancy is a false alarm due to some villain's scheme, creating chaos and misunderstandings within the crew.
One possible plot twist could be that they initially plan to keep the pregnancy a secret but then someone discovers it and spreads the news, causing chaos in their lives. Maybe their families have different reactions, with some being supportive and others not so much.
Perhaps a plot twist could involve some sort of magic that endangers Juvia's pregnancy. Gray then has to go on a dangerous quest to find a cure or a way to protect Juvia and the unborn child. He might have to face his own inner demons along the way as well, since he has always been a bit of a loner and this new responsibility scares him.
One possible plot twist could be that it was an unexpected pregnancy. Maybe they were just starting their relationship and this news completely changes their plans. They might have to deal with reactions from their families and friends, some of whom could be very supportive while others might be shocked or disapproving.
One possible plot twist could be that the pregnancy is a result of some Capitol - engineered experiment. Maybe they were secretly given a fertility - enhancing drug during their time in the Games. This would add a whole new layer of danger and mystery to the story as they try to figure out what the Capitol's motives are and how to protect their unborn child.