One idea could be to focus on how Astrid and Hiccup prepare for the baby. They might start building a new addition to their home on Berk. Hiccup could be super protective, while Astrid is determined to still be involved in dragon - related activities as much as she can until she can't anymore.
One common theme is the relationship between Astrid and Hiccup. Their dynamic changes as they prepare for parenthood. Hiccup may become more nurturing and Astrid might show a softer side. Another theme is the anticipation of the new baby in the village. The villagers might start making preparations, like building a new crib or knitting baby clothes.
There would be a shift in their dynamic as they prepare for a family. Hiccup, who is used to being adventurous, would have to focus more on home and stability. Astrid, while still strong - willed, would become more nurturing. They would need to find a new balance in their relationship, between their old selves and their new roles as parents - to - be.
Astrid's character could develop in many ways. She may become more empathetic towards the other mothers in Berk. Before, she was mainly focused on her warrior duties, but now she can relate to the women who have to take care of their families. She might also learn to rely on others more, especially Hiccup, as she goes through the physical and emotional changes of pregnancy.
One idea could be that Astrid discovers she's pregnant during a time of relative peace in Berk. She initially tries to keep it a secret from Hiccup because she's not sure how he'll react. As the story progresses, she starts to show signs and has to face the reality of sharing the news. Meanwhile, the village is preparing for a new celebration, and Astrid is worried about how the pregnancy will affect her role in it.
In many HTTYD fanfictions where Astrid is pregnant, it often explores how she and Hiccup handle this new chapter in their lives. It could involve Hiccup being overly protective, or Astrid trying to still be as independent as she used to be while dealing with the physical changes. For example, she might continue to train dragons in a more limited way, much to Hiccup's worry.
There is also 'Hiccup and Astrid's Adventure'. This one takes them on a journey to a new land. The way it describes their interactions and how they rely on each other is really engaging. The author has a great writing style that makes you feel like you're right there with Hiccup and Astrid during their adventure.
There's also 'The Bond of Hiccup and Astrid'. This fanfiction takes a different approach. It focuses on their love through small, everyday moments. For example, how they train their dragons together and steal glances at each other. It's a very sweet and simple story that really shows their deep connection.
Well, start with setting the scene. Maybe it's a sunny day on Berk when Astrid first realizes she's pregnant. She could be out with Stormfly and suddenly feel a bit off. Then, for the plot, you can include how she tells Hiccup. He might be overjoyed and a bit clumsy in his excitement.
Archive of Our Own (AO3) is also a great place. It has a very inclusive and diverse set of fanfictions. Just search for 'httyd hiccup and astrid' and you'll get a bunch of results. The site also has good tagging systems so you can easily find stories with the elements you like, such as adventure or romance.