One great fanfiction in this theme might be 'The New Beginning' where it beautifully depicts their journey into impending parenthood. It shows how Meliodas is both excited and a bit nervous, and Elizabeth is full of anticipation.
There could be some stress on their relationship too. The responsibilities of impending parenthood might cause some arguments. For instance, they might disagree on where to raise the child or how to handle the child's potential powers. But these conflicts would ultimately strengthen their bond as they work through them together, learning more about each other in the process.
There are various fanfiction platforms where you can find such stories. For example, Archive of Our Own (AO3) is a great place to start. Just search for 'Elizabeth and Meliodas pregnant' on the site, and it will show you a list of relevant fanfictions.
In fanfiction, the Meliodas and Elizabeth kiss often represents a culmination of their deep emotional connection. It can be a moment of great passion and relief. For example, it might signify the overcoming of various obstacles they faced in their relationship, whether it was external threats or internal doubts. It's a way for the writer to show the strength of their love and the hope for their future together.
One plot idea could be that they face challenges from outside forces who are either jealous or see their unborn child as a threat. Maybe an old enemy tries to target Elizabeth during her pregnancy, and Meliodas has to go to great lengths to protect her and their future family.
Diane would probably be overjoyed. She's always been close to Meliodas and Elizabeth, and she would likely offer to protect them and help out in any way she can. Maybe she'd use her giant strength to build a special place for them to stay during the pregnancy.
In fanfiction, the kiss between Meliodas and Elizabeth can be a very powerful symbol. It can represent not only their love for each other but also the hope for the future of their world. It could be that their love is seen as a force that can bring peace or change things for the better. It's also a way for the author to connect with the readers' emotions on a deeper level, as many readers are invested in the relationship between these two characters.
The reactions of their friends and allies. In some fanfictions, Diane might be overly excited and offer to help with baby - sitting in the future. King could be a bit more reserved but still supportive. These interactions add depth to the story.
Another plot twist might be related to Elizabeth's memories. Since she has had multiple reincarnations, there could be something in her past memories that affects the pregnancy. For example, a past life's vow or curse that she was unaware of starts to have an impact on her current state of being pregnant.