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.
Some friends might be overjoyed. For instance, Stiles could be really excited and start making all kinds of plans for the baby shower. He might also be a bit overprotective, constantly checking in on Lydia and making sure she's taking care of herself.
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.
There could be fanfictions that focus on their teamwork. In some stories, they are paired up on a special mission within the supernatural world of their universe. They have to rely on each other's unique abilities, like Derek's werewolf strength and Lydia's banshee powers, which makes for an exciting read.
Another place could be FanFiction.net. Although the interface might not be as modern as AO3, it still has a good number of Derek and Lydia fanfictions. You may need to do a bit more sifting through different categories to find the ones you like, but it's definitely worth a try.
One idea could be to focus on how Odette and Derek prepare for the baby. For example, they could be decorating the nursery together, choosing colors and furniture. Maybe Derek is really into building the crib himself, while Odette is more concerned with the softness of the bedding.
It could be her long - time boyfriend. They might have been planning for a family in the future, but the pregnancy comes as a bit of a surprise earlier than expected.
Yes, there might be some out there. You can try searching on fanfiction websites like Archive of Our Own. They have a large collection of various fanfictions, and it's possible to find ones related to Beetlejuice and Lydia in such a situation.
During the pregnancy, they could face a lot of stress and challenges. These difficulties can either make their relationship stronger or put a strain on it. If they communicate well and support each other, they'll grow closer. For example, Derek might be the one who gets up in the middle of the night to get Lydia whatever she craves, and in return, Lydia could be more understanding of Derek's concerns about protecting their new family. It's all about how they handle the changes that come with the pregnancy.
A simple plot could be that Odette discovers she's pregnant and they both are initially in shock. But then they quickly start to get excited. They could go to the doctor together for the first ultrasound and be amazed at seeing the tiny figure on the screen.