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.
A plot twist could be that their pregnancy is endangered by an enemy. The enemy might try to harm the unborn child because they fear the power it could possess in the future. So, Alice and Jasper have to go into hiding and protect the pregnancy at all costs, which would make for a very suspenseful story.
One possible plot twist could be that a long - lost relative of Bella shows up and tries to stop the wedding because they have some dark secret about the Cullens. Another could be that a new vampire coven arrives and challenges the Cullens right before the wedding, forcing Bella and Jasper to postpone it while they deal with the threat. Maybe there's also a twist where Bella discovers a new power within herself on her wedding day that changes the whole dynamic of the relationship with Jasper and the Cullen family.
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.
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.
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.
One possible plot twist could be that the father of the baby is a mystery. Maybe Tiffany has been involved with multiple characters and she's not sure who the father is. This could lead to a lot of drama and tension as she tries to figure it out.
A plot twist might be that Daenerys and Jon Snow find out that the pregnancy is not a normal one. It could be that the child has some sort of special powers or abilities even before birth. This could lead to various factions either trying to protect or destroy the unborn child. Also, there could be a twist where the pregnancy causes a rift between them because they have different ideas on how to raise and protect the child in a world full of danger and political unrest.
Maybe there's a new threat in the form of a political faction that wants to undermine their relationship. They try to spread rumors that the baby isn't Peeta's or that Katniss is using him for power. This forces Katniss and Peeta to fight not only for their family but also for their reputations in the district.