One great Loki and Sif fanfiction is 'A Different Path'. It explores an alternate universe where Loki and Sif have to team up for a quest. The story is well - written, with great character development. It shows a side of Loki that is more vulnerable and a strong - willed Sif.
A plotline might involve Loki and Sif coming to terms with their relationship while dealing with the pregnancy. For example, they could have had a rocky relationship before and the pregnancy forces them to re - evaluate their feelings for each other. There could also be a plot where they have to protect the unborn child from some sort of threat, either from within Asgard or from other realms.
One popular theme is redemption. Loki is often a character in need of redemption, and Sif can be the one who either helps him on that path or is a witness to his journey. For example, in many fics, Loki tries to make up for his past wrongs against Sif and Asgard.
Love and loyalty are also prevalent themes. Fanfictions show how their love for each other grows and endures despite the odds. They might face external threats or internal conflicts, but their loyalty to one another remains strong. This theme helps to create a more emotional and romantic aspect to the stories about their married life.
One common theme is redemption. Loki often has to redeem himself in the eyes of Sif for their love to develop. For example, in many fanfics, he might start off as a trickster causing trouble for Sif, but then he changes for the better.
I'm not sure about specific Loki and Sif pregnant fanfiction off the top of my head. But you can try searching on fanfiction websites like Archive of Our Own. They usually have a wide range of fanfictions and you can use the search filters to look for ones related to Loki, Sif and the pregnancy concept.
Another plotline could be the challenges they face during the pregnancy. Since Loki has his mischievous nature and Sif is a strong - willed warrior, they might have different approaches to the pregnancy. There could be conflicts and then reconciliations as they figure out how to deal with the situation together. This can involve things like dealing with Asgardian traditions regarding pregnancy and childbirth.
When writing the 'lemon' aspect, if it's appropriate for your story, be tasteful. Focus on the emotional connection between the characters during these scenes. Use descriptive language to show their feelings rather than just the physical actions. Also, the setting is important. You could set it in a secluded part of Asgard, like a forgotten garden or a hidden chamber. This can add an element of secrecy and intimacy to their encounter. And don't forget to have a good plot that leads up to and follows these moments, so the story doesn't feel like it's just about the 'lemon' parts.
One great Loki and Sif baby fanfiction could be about the challenges they face in raising a baby with Loki's mischievous nature and Sif's warrior strength. Maybe the baby inherits some unique powers that they have to figure out how to handle.
Fanfiction.net is also a good place to look. There are many writers who contribute different types of fanfictions. However, the quality can vary, so you might need to sift through a bit to find the really good Loki and Sif baby fanfiction.