Perhaps a plot twist could be that Elena discovers she's pregnant, but Elijah has lost his memory due to some dark magic. So, she has to deal with the pregnancy on her own while also trying to find a way to restore his memory. This would add a lot of emotional turmoil to the story.
A really interesting plot twist could be that the baby has some sort of special power that is both a blessing and a curse. The Originals and the vampires in their world might see the baby as a threat or a valuable asset. This would put Elijah and Elena in a very difficult position as they try to protect their unborn child from those who would use it for their own gain.
One possible plot twist could be that the baby has some unique supernatural powers that neither Elijah nor Klaus expected. For example, it might be able to control time or have the ability to travel between different dimensions. Another twist could be that there is a prophecy about this baby that endangers its life, and the characters have to fight to protect it from various forces that want to use or destroy it. Or perhaps, the baby's true father is revealed to be someone else entirely through some sort of magical or scientific discovery.
One interesting plot twist could be that the pregnancy is a result of a magical spell gone wrong. Maybe a witch with a grudge against Elena cast a spell that made her pregnant with Elijah's child against their will. This would add a lot of drama as they have to figure out how to reverse it while also dealing with the reactions of their friends and family.
One plot idea could be the challenges they face in keeping the pregnancy a secret from their enemies. Another could be how they prepare for the arrival of the baby in a world filled with supernatural threats. For example, they might have to find a safe place away from the constant power struggles in their supernatural community.
Perhaps a plotline where Elena discovers she's pregnant and is initially scared. Elijah, being the noble vampire he is, vows to protect her and the baby at all costs. They could then go on a journey to find a safe place, away from the vampire and werewolf politics that constantly threaten their lives. Along the way, they face challenges that test their relationship and their will to keep the baby safe.
One possible plot twist could be that the pregnancy is part of a prophecy. Maybe there's an ancient prophecy that states a child born from Klaus and Elena will either bring great destruction or be the key to saving the supernatural world. This would add a layer of mystery and danger to the story.
One possible plot twist could be that a long - lost relative of Elena shows up to oppose the marriage. Maybe this relative has some ancient grudge against the family that Elijah is from. Another twist could be that a powerful witch casts a spell on Elijah, making him forget his love for Elena right before the wedding. Then Elena has to go on a quest to break the spell.
Well, a plot twist could be that the baby has some unexpected powers. Since Klaus is a hybrid and Elena has her own unique connection to the supernatural world, the baby could inherit a combination of powers that no one has seen before. It could also be that Elena discovers she's pregnant but then loses the baby due to some dark magic, which leads to Klaus going on a rampage. Then, later, it turns out the baby is still alive but has been hidden away by a secret group who wants to use it for their own ends.
One possible plot could be that Elijah and Elena find out about the pregnancy unexpectedly. They then have to deal with the reactions of their friends and family. There might be some who are happy and supportive, while others are shocked or even against it. They would also need to figure out how to prepare for the baby, like finding a suitable place to live and getting all the necessary baby items.
Perhaps a plot twist could be that Klaus has a change of heart. He starts off as his usual self - centered, power - hungry self, but as Elena's pregnancy progresses, he begins to develop real feelings for her and a sense of protectiveness towards the unborn child. This could lead to him making sacrifices and even allying with his former enemies to keep Elena and the baby safe.
Well, one plot twist could be that the father of her baby is not who everyone suspects. Maybe it's a character who has been secretly in love with her all along. Another could be that there are some supernatural elements affecting her pregnancy, like a curse that changes the nature of the baby.