Another plot could involve the reactions of their friends. Pikachu might be really curious and try to help in his own little way. And the other Pokémon friends could also offer their support in different ways, like gathering special berries that are good for Latias during pregnancy.
One plot idea could be that Ash and Serena discover they're pregnant during their journey. They then have to decide whether to continue traveling or find a safe place to settle for a while. Another could be that they face challenges from Pokémon battles while Serena is pregnant, and Ash has to be extra cautious to protect her and their unborn child.
One plot idea could be that they embark on a journey to find a special place to raise their child. They might face challenges along the way, like dealing with wild Pokémon that are more aggressive due to the new energy they sense. Another could be that they start a Pokémon training school for their unborn child and other kids in the region, teaching them about Pokémon care and battle strategies.
One idea could be that Ash forms a special bond with Latios and Latias while on a journey in a new region. They help him discover a hidden power within himself. For example, Latios might be able to sense when Ash is about to make a wrong move in a battle and communicate it to him telepathically.
One idea could be that Ash and Latias team up to save a group of Pokémon from an evil organization. Ash uses his battle skills and Latias uses her psychic powers.
One idea could be focusing on how Ash's friends react to the news. They might be shocked at first but then rally around to support her. Another could be Ash dealing with the physical and emotional changes during pregnancy while still trying to pursue her goals.
One idea could be that they discover the pregnancy during their travels and have to figure out how to balance their adventures with the upcoming baby. For example, they might need to find a safe place to stay for a while.
One plot idea could be that they go on an adventure together while May is pregnant and face some challenges related to protecting the unborn child. For example, they might encounter some wild Pokémon that are unusually aggressive, and Ash has to use his skills to keep May and the baby safe.
One idea could be that Ash has to quickly grow up and take on more responsibilities to support his mother during her pregnancy. He could start doing odd jobs around town to earn money for things like baby supplies.
One idea could be exploring how Yennefer deals with the physical and emotional changes during pregnancy while still being a powerful sorceress. Maybe she has to find a way to protect her unborn child from the many enemies she has made.
One idea could be exploring how she and her partner (like Percy) adjust to the news. They might have to deal with the reactions of their friends and family. Another could be the challenges she faces during the pregnancy, like her still wanting to be involved in heroic adventures but having to be more cautious.