Another theme is the support system around Jace. His friends or family coming to his aid when he's hurt and how their relationships evolve during this time. For example, in some fics, a character who was distant before becomes closer as they help Jace through his pain.
There is a story titled 'Hurt Jace: The Unseen Struggles' which shows Jace in a rather vulnerable state. He has to deal with an unexpected injury and the way he copes with it while still trying to be strong for his friends makes for an interesting read.
Their relationship would become more centered around the baby. They would have to make decisions together for the sake of their child, which would strengthen their bond.
The relationship would evolve significantly. Before the baby, they were mainly focused on their own adventures and relationship. But now, they are parents. They would need to support each other in different ways. For instance, Jace might be more protective of Clary and the baby. Clary would be more nurturing, and they would both have to learn to balance their duties as Shadowhunters with their new family life.
Jace will probably face a lot of guilt. His cheating not only hurt Clary but also has implications for the unborn child. He might find himself ostracized by their friends who side with Clary. Also, his reputation within their community in the fanfiction world could be severely damaged. If he realizes his mistake and wants to make amends, he'll have a long and difficult road ahead to earn Clary's forgiveness and trust again.
It depends on the fan base. Some fans are interested in more mature and complex storylines that might fall under Rated R, such as those involving intense emotional turmoil or more graphic action scenes. However, others may prefer more family - friendly or PG - 13 level fanfiction.
I'm not entirely sure if there is a specific 'Jace Superstar Clary Pregnant Fanfiction'. However, considering how creative fans can be, it wouldn't be a surprise. Some fans like to explore different life situations for their favorite characters. You could also check out Tumblr, as sometimes people share links to interesting fanfictions there.
One of the main themes is the clash of cultures. Harry is from the wizarding world of Hogwarts and Jace is from his own unique world. In fanfiction, this leads to interesting situations as they try to understand each other's ways. Another common theme is the search for identity. As they interact, they often question who they are in relation to the other. And of course, there is the theme of heroism. They both are heroes in their own right, and in fanfiction, they often team up to save the day.
These fanfictions usually build on the existing relationship dynamics from the original source material. They might expand on the challenges that Jace and Clary face as a couple, like dealing with the secrets in their world or the opposition from other characters. And the 'lemon' parts are written to add a bit of spice and heat to their relationship portrayal.
Love is a very common theme. Since they are a couple in the original series, fanfiction often explores different aspects of their love, like how they overcome obstacles to be together. Another theme is adventure. Fans like to put Jace and Clary in new adventures that are related to their world of shadowhunters.