Perhaps the pregnancy is unexpected, and they initially struggle with how it will affect their Jedi duties. They might worry about how to balance raising a child with their commitment to the Jedi Order. Luke could seek advice from old masters in the Force, like Yoda's spirit, while Mara tries to come to terms with the physical and emotional changes.
One possible storyline could be that they face challenges from the dark side while Mara is pregnant. Maybe some remnants of the Empire try to target them because they see the unborn child as a potential threat or a powerful force for the light side. They would then have to go into hiding and rely on their friends and allies to keep them safe.
There are some fanfictions that might explore such a scenario. However, it depends on different authors' creativity and the specific plotlines they develop. Some fanfic writers might be interested in exploring the relationship between Mara Jade and Luke Skywalker in such a context, but it's not a mainstream or canon storyline in the official Star Wars universe.
One possible plot could be them going into hiding to protect the unborn child from their enemies. Since they are both important figures in the Star Wars universe, there would be many who might want to harm the child for various reasons, like power or revenge.
Sith cults could also be antagonists. They might sense the power of the unborn child in the Force and want to turn it to the dark side. They could launch attacks on Luke and Mara to either kidnap Mara or influence the unborn child through dark side magic or the Force.
One great fanfiction could be 'The Bond of Skywalker and Jade'. It delves deep into their relationship, exploring how their Force sensitivities interact. Another is 'Luke and Mara: A New Adventure' which takes them on a journey across the galaxy to face a new threat. There's also 'Mara Jade's Choice' that focuses on Mara's internal struggles regarding her feelings for Luke.
Some popular authors are 'JediWriter123'. Their stories often have a great balance between action and romance for Luke and Mara. Another one is 'StarWarsFanatic456' who is known for really delving into the characters' emotions. And 'GalaxyTalesAuthor' also writes some great fanfiction about them.
One possible storyline could be Mara Jade dealing with the challenges of her pregnancy while also facing threats from her past enemies. Maybe she has to hide her pregnancy to keep herself and the unborn child safe.
One interesting plotline could be their first meeting in a different context. Maybe instead of how it happened in the official lore, they meet during a smuggler's run. Luke is on a mission to retrieve an important Jedi artifact and Mara Jade, working undercover for the Empire at the time, is also after it. Their encounter could lead to a series of adventures as they battle pirates and other foes while trying to outwit each other.
Character growth is another major element. Mara Jade might start off as a bit of a mystery, and through her interactions with Luke, she evolves. Luke, too, may change as he gets closer to Mara, learning new things about himself and the Force, as seen in some fan fictions where he discovers new aspects of the Force through her influence.
One great Mara Jade - Luke Skywalker fan fiction is 'Heir to the Empire' series. It really delves into their relationship in an interesting way, with great character development and a captivating plot that keeps you hooked. The way it weaves their individual stories together is quite remarkable.
Maybe in the fanfiction, Luke witnesses something so devastating that he loses faith in the Jedi way. For example, if the Jedi Order fails to prevent a great catastrophe. This could push him towards the Dark Side as he seeks a more radical solution to bring order. He might start using aggressive and unethical means, like Vader did, believing it's for the greater good.