Well, it depends. Fan writers have a lot of creativity. They could create alternate storylines where the egg has special powers or where Valka has to protect it from new threats.
Their relationship would become more centered around the future. They'd have more serious conversations about how to raise the child. Valka might be more open about her past experiences with dragons to Stoick, so they can decide how to share that part of her life with the baby. And Stoick would be more cautious in his actions, not wanting to put Valka or the unborn baby in danger.
It's hard to say if it's common. Since Valka is a fictional character, we don't really have data on her fictional reading habits. But in the context of the fandom, it could be seen as something that would be cool if she did, as it would show her interest in the fan - created content.
Since I'm not familiar with the specific 'valka erotic story', it's hard to say if there is a non - adult interpretation. But often, if a story has an adult theme, it can be reimagined in a more family - friendly way by focusing on other aspects such as the characters' relationships in a non - sexual way.
One common theme could be the anticipation and excitement surrounding the new life. It might explore how Valka and those around her prepare for the baby.
Rather than seeking 'lemon' fanfics which are inappropriate, you could look for fanfics that explore the emotional bond between Hiccup and Valka. For example, there might be ones where they go on adventures together and strengthen their family ties. These can be found by simply typing 'Hiccup and Valka positive relationship fanfics' into your search engine.
Finding valka pregnant fanfiction can be a bit of a hunt. You could also try reaching out to fellow fans in relevant fan communities or forums. They might be able to point you in the right direction. Some smaller, niche - based fanfic platforms might also have such stories, but they are often harder to discover.
Mainly, it's Hiccup and Valka. Hiccup is the protagonist we know from the 'How to Train Your Dragon' series, always curious and eager to learn more about dragons. Valka, on the other hand, is a mysterious figure who has her own set of skills and knowledge regarding dragons. When they meet in the fanfiction, their different personalities and experiences collide, creating an interesting dynamic that drives the story forward.