Well, a possible plot is that there are some dark forces that target Lucy because of her unborn child. Maybe they believe the baby will have some special powers. Laxus then has to go on a journey to find a way to protect them. And as for their relationship, it could be strained at first because of the stress, but they gradually grow closer as they face the challenges together. Plus, there could be a sub - plot about how Lucy's celestial spirits react to the news. Some might be overjoyed and offer their own unique forms of protection.
A plot idea could be that Laxus and Lucy decide to keep the pregnancy a secret from the guild at first. They want to enjoy this private moment just between them. As Lucy's pregnancy progresses, she discovers some new magical abilities that seem to be related to the baby's growing power. Laxus, on the other hand, becomes more protective and starts training harder to be able to safeguard his family. Meanwhile, a mysterious figure from Laxus' past resurfaces, and it's unclear whether they are a friend or foe in relation to the baby.
One idea could be that they discover the pregnancy unexpectedly. Maybe they were in the middle of a big adventure in their magical world and then Lucy starts showing signs. It throws them into a new set of challenges as they have to balance their duties in their guild with preparing for a new life.
Another plot could be that Lucy gets pregnant through some sort of magical accident. She then has to figure out how to deal with the changes in her body and magic while also trying to find a way to reverse the 'accident' if she wants to. But during this process, she starts to form a special connection with the unborn child and has a change of heart.
One idea could be focusing on how their guild mates react. Maybe there could be a big celebration in the guild hall, with everyone bringing gifts and sharing their excitement. Another plot could revolve around their preparations for the baby, like choosing a name or decorating the nursery.
I'm not sure if there is a specific fanfic with that exact plot. There are a vast number of fanfics out there in the Fairy Tail fandom, but it would take some searching through various fanfic platforms to know for sure. Some popular fanfic sites like Archive of Our Own or FanFiction.net might be good places to start looking if you're interested in such a story.
Laxus would experience a significant shift in his priorities. His focus would no longer be solely on his own power and status within the guild. Instead, he'd be more concerned about providing a stable and safe environment for his child and Lucy. This might lead to him mending some of his past relationships within the guild. Lucy, on the other hand, would develop a deeper sense of purpose. Her pregnancy would make her realize the importance of family and legacy. She'd start to pass on her knowledge, perhaps about celestial magic, to the unborn child in unique ways, and this would also strengthen her bond with Laxus as they both look forward to the future together.
Well, a great plot could involve them facing some challenges during the pregnancy. For instance, Mirajane might have some difficulties with her magic due to the pregnancy hormones. And Laxus would be super protective, which could lead to some interesting conflicts within the guild when he overreacts to perceived threats. Also, they could discover some old family traditions related to pregnancy and childbirth that they decide to incorporate.
Maybe the story could revolve around how their guild mates react to the news. Some might be overly excited and start planning big parties, while others could be more cautious and offer practical help, like setting up nurseries for them. It would show the strong community within the guild.
One idea could be that Lucy's pregnancy is unexpected and she has to deal with the reactions of her friends and family. Some might be overjoyed while others are worried. Another could be a story where the father of the baby is a mystery and Lucy goes on a journey to find out who it is. Maybe she discovers some secrets about her past relationships along the way.
One plot idea could be how Lucy adjusts to her new state while still being part of the Fairy Tail guild. Maybe she has to take on less dangerous missions at first and her friends rally around to protect her. For example, Natsu could be overly protective, getting into comical situations as he tries to keep her out of harm's way.
One great fanfiction could be 'A New Beginning for Laxus and Lucy'. It beautifully portrays their journey into parenthood. The author does an amazing job of showing how they adjust to the idea of having a baby and the changes it brings to their relationship.