One possible plot could be that they face challenges in Narnia while Susan is pregnant. Maybe there are threats to the kingdom that they have to deal with together, all while preparing for the arrival of their child. Caspian might be extra protective of Susan, and they could rely on the help of their friends in Narnia.
Susan could develop into a more nurturing figure. Since she's pregnant, she might become more in tune with the needs of others in Narnia, not just her own family. Caspian, on the other hand, might grow in his sense of responsibility. He now has a family to protect, so he may make different decisions regarding the kingdom.
Perhaps a plotline where the pregnancy is unexpected and it throws Susan Caspian's life into chaos. She might have to make difficult decisions regarding her future, her relationships, and her own identity. There could also be a plotline where the father of the baby is in some sort of mystery or danger, adding more drama to the story.
I don't know of any specific Susan and Caspian pregnant fanfiction to recommend. It's a rather specific concept, and while there could be some out there, it may be a bit hard to find. Maybe you could start by looking at the works of well - known fanfiction writers in the Narnia fandom and see if any of them have explored this idea in their stories.
A possible plot is that Susan discovers she is pregnant during a time of unrest in Narnia. Caspian is worried about how to protect her and the unborn child. They decide to go into hiding for a while in a secret part of Narnia. There, they live a simple life, and Caspian learns to be more self - sufficient, like fishing and hunting for food. As the pregnancy progresses, they form a deeper bond. Eventually, they return to the kingdom when things have calmed down, and they are welcomed with open arms as they await the birth of their child.
One possible fanfiction could start with Susan discovering she is pregnant. Caspian is overjoyed but also filled with a sense of responsibility. They start preparing a nursery in the castle, with Caspian bringing in the finest woods and fabrics. Susan spends her days knitting baby clothes, dreaming of their future child. Their friends in Narnia are excited too, and they all gather to offer their support and gifts. As the pregnancy progresses, they face some challenges, like when Susan has a difficult day of morning sickness, but Caspian is always by her side, bringing her soothing herbal teas.
I'm not sure specifically about 'Susan Caspian pregnant' fanfiction. You could try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net. They have a wide range of fan - created stories and you might be able to find something related there.
The story could have a big impact on the magic in Narnia. Maybe the baby has a unique connection to the magic of the land, and its presence could either strengthen or disrupt the existing magical balance. Also, the idea of a new heir could inspire new quests and adventures, as various characters in Narnia would want to be part of the baby's life and future.
I'm not sure if there is specific fanfiction about Susan being pregnant in The Chronicles of Narnia. Fanfiction can cover a wide range of topics, but this might be a rather unorthodox or less common theme. It could potentially exist in some corners of the vast fanfiction world, but it's not something that is widely known or mainstream within the Chronicles of Narnia fanfiction community.
One possible theme could be love and commitment. The pregnancy would force them to reevaluate their relationship and show how deeply they care for each other. Another theme might be the impact on Narnia. As Caspian is a prince, there could be political implications of this union and the upcoming child. Also, there could be a theme of sacrifice, like Susan might have to sacrifice some of her own desires or plans for the sake of the baby and Caspian.