One idea could be that Lydia discovers she's pregnant and has to deal with the reactions of her friends and family. Maybe Stiles is the father and they have to figure out how to handle this new situation while also dealing with the supernatural threats in their town.
In a Lydia Martin pregnant fanfiction, the plot could revolve around her decision - whether to keep the baby or not. She could be facing a lot of pressure from different sides. Her friends might be supportive but some of the adults in town could have different opinions. Meanwhile, she also has to continue her studies and deal with the social implications of being a pregnant teenager in a small town.
Perhaps in the fanfiction, Lydia is pregnant in a post - apocalyptic world. She has to find ways to protect herself and her unborn baby from various threats. This could involve teaming up with unexpected allies and facing difficult moral choices along the way.
Perhaps they find out they're pregnant unexpectedly. Stiles starts making all these plans for their future as a family right away. Lydia is more cautious, thinking about how this will change their lives completely. Their friends could also play a big role, some being super supportive while others might be skeptical. And they could have to deal with family reactions, like Stiles' dad being really excited and Lydia's parents having mixed feelings.
Stiles would be a very likely candidate as they have a close relationship in the show. Their banter and connection could easily lead to a situation where they end up having a baby together in a fanfiction.
One idea could be that Lydia's younger sister discovers Liam's werewolf secret and has to keep it from Lydia. Maybe she stumbles upon him during a full moon transformation and they form an unexpected bond over the shared secret.
Maybe there's a mystery surrounding the pregnancy. Since they are in a world full of the supernatural, the baby could have some special powers even before birth. Some of the other characters like Scott and Stiles might suspect that there's something unusual about the pregnancy. They could try to investigate, which causes some tension between them and Lydia and Parrish, who just want to enjoy the pregnancy without all the scrutiny. But in the end, they all come together when they realize they need to protect the baby from some external supernatural threat.
One idea could be that they face challenges from their families who are initially not supportive of their relationship now that Lydia is pregnant. Another could be that they discover some sort of supernatural complication related to the pregnancy. For example, the baby might have special powers that start to manifest during the pregnancy and they have to figure out how to deal with it.
Well, perhaps in the fanfiction, Martin and Ruthie discover they're pregnant unexpectedly. They then start to attend parenting classes together. Martin could be really nervous about becoming a father but Ruthie is very calm and reassuring. They could also start shopping for baby items and have cute arguments over the color of the nursery.
One possible plot idea could be about Lydia's journey through pregnancy. Maybe she discovers she's pregnant unexpectedly and has to deal with the reactions of her family and friends. For example, her parents might be disappointed at first if she's young, but then gradually come around to support her. Another aspect could be how she copes with the physical and emotional changes. She might find solace in a new friendship or an old acquaintance who has also been through pregnancy.
I'd recommend 'Lydia's Hidden Powers'. This fanfiction delves deep into Lydia's potential powers that were perhaps not fully explored in the original. It has a lot of action and character development. You'll find yourself hooked from the very first chapter as it builds up the mystery around Lydia's newfound abilities.
One idea could be that they face unexpected challenges during the pregnancy. For example, Derek discovers a family curse that might affect the baby, and they have to find a way to break it. Another could be that Lydia has premonitions about the future of their child, which leads them on a journey to protect the unborn baby from a hidden danger.