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.
Well, at the start of the pregnancy, they might be a bit scared and uncertain about what's to come. But as time passes, they could start to plan for their future together. Derek may start to learn more about Lydia's needs and wants, not just related to the pregnancy but also in general. Lydia, on the other hand, might start to rely on Derek more, and this new level of dependence can deepen their bond. They might also start to have more serious conversations about their values and how they want to raise their child, which would bring them closer together as they realize they have common goals for their family.
Derek could become more responsible. He might start taking on more household chores, like cooking healthy meals for Casey, and be more protective of her. Casey, on the other hand, could develop more patience. Dealing with the hormonal changes and the physical discomfort of pregnancy, she learns to control her temper better and communicate more effectively with Derek.
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.
They could grow closer as they experience the joys and fears of the pregnancy together. For example, sharing the first time they feel the baby move can be a really special moment that deepens their bond. Also, they might have to rely on each other more for emotional support, especially when facing difficulties like morning sickness or concerns about the baby's future.
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.
At first, their relationship might start with a lot of bickering. Beetlejuice is a wild character and Lydia is strong - willed. But as time goes on, they start to understand each other better. Beetlejuice shows Lydia the fun and freedom of the Netherworld, and Lydia shows Beetlejuice that there's more to the living world than just scaring people. This mutual understanding paves the way for their love to grow and eventually lead to marriage.
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.
Their relationship could become stronger. The pregnancy might make them more protective of each other. Kai would be more attentive to Cinder's needs, and Cinder would feel more connected to Kai as they are about to start a family together.
Their relationship could deepen with Goliath becoming even more protective of Elisa. He would be constantly on guard to ensure her safety. Elisa, in turn, might rely on Goliath more, creating a stronger bond between them.
One way is through communication. They may have deep conversations about their future as parents, their hopes and dreams for the baby. Roy might also start to take on more domestic tasks to support Riza, which shows his commitment. And Riza could be the one to encourage Roy in his career, even while pregnant, showing that they support each other fully. Another aspect is physical affection. Gentle hugs and kisses can show their closeness during this time.