Zuko's personality could be shown as more tender and caring than ever. He might be constantly worried about Mai's well - being and that of the baby. His sense of responsibility would be heightened. Mai, on the other hand, while still maintaining her dry sense of humor, would show a more vulnerable side. She may not be as openly emotional as Zuko but her actions, like making sure the nursery is safe, would show her love and care for the unborn child.
One possible plot could be that Zuko and Mai are initially shocked by the pregnancy. They then start to prepare for the baby's arrival. Zuko might be a bit overprotective, while Mai tries to keep her cool. Their friends could be excited or worried, and there could be challenges like dealing with the public's reaction as they are important figures. Maybe they face some threats to the unborn child which they have to overcome together.
Maybe a plot where Mai is kidnapped by enemies of the Fire Nation who want to use her to get to Zuko. Zuko then embarks on a dangerous rescue mission. Along the way, he realizes just how much Mai means to him. Or a story where Zuko and Mai are forced into an arranged marriage by Fire Nation politics. At first, they resist, but as they spend more time together, they start to develop real feelings for each other that go beyond the political arrangement.
One plotline could be the challenges they face in the Fire Nation. Since Zuko is the Fire Lord, there might be political implications of his partner being pregnant. People might try to use the situation to their advantage or there could be concerns about the safety of the unborn child.
Zuko can be developed by exploring his role as a leader within the context of his marriage. He may struggle to balance his duties as Fire Lord with his time for Mai. This internal conflict can show his character's depth. He could also develop new bending techniques influenced by his love for Mai. As for Mai, she can develop by getting involved in more political matters, standing by Zuko's side and using her intelligence to influence decisions. She could also start to make more friends in the palace, which would change her somewhat solitary nature.
Their relationship would likely become more intimate and protective. Zuko would be more protective of Mai, constantly worried about her well - being during the pregnancy. Mai would probably become more dependent on Zuko for emotional support.
One plot idea could be that they initially struggle with the news. Zuko might be worried about how his role as a leader would be affected while Mai is dealing with the physical and emotional changes. They could face challenges from the Fire Nation's traditional views on pregnancy and family. Another idea is that they go on a journey to find a safe place for their child to be born, away from the political unrest in the Fire Nation.
You can try looking on fanfiction platforms like Archive of Our Own (AO3). It has a vast collection of fanfictions on various topics, including those related to Mai and Zuko. Just use the search function and type in relevant keywords like 'Mai Zuko pregnant' to find the stories you're interested in.
Well, the theme of family also often comes up. Zuko's family situation is complicated, and Mai is also affected by her family's expectations. Fanfics may explore how their relationship is influenced by their families. For example, how Zuko's relationship with his father affects his relationship with Mai. Also, the theme of growth is common. Both Zuko and Mai grow as characters in fanfics, learning more about themselves and each other.