Another plot could be that Severus leaves because he is afraid of the implications of Harry being pregnant. Maybe it goes against his beliefs or the society in the wizarding world they live in. Harry then has to face the judgment of others. As the story unfolds, Harry might prove to Severus and the world that they can overcome these obstacles, which could eventually bring Severus back.
In some fanfictions, it might be that Severus leaves due to some external threat that he believes will harm Harry and the unborn child if he stays. So, he sacrifices his relationship with Harry for their safety. Harry, on the other hand, is left heartbroken but determined to raise the child alone. Later, Severus might return when he realizes he can protect them after all, leading to a reconciliation.
One possible plotline could be that Sakura decides to raise the child on her own. She focuses on her medical ninjutsu to provide for the baby. Another could be that she tries to find Sasuke again to make him take responsibility. Maybe she faces challenges from the village as a single mother, but her friends support her through it all.
Another plot could involve Lucy leaving because she discovers a secret about the father of her baby that makes her feel she can't stay. For example, if she finds out he has a dark past or is involved in something illegal. This would lead to her making the difficult decision to leave on her own.
Maybe Harry leaves for America to escape the fame and the constant reminders of his past in the UK. In America, he could start anew and try to live a more normal life. He could meet new friends who don't know about his heroic deeds in Britain and form relationships based on who he is now, not what he's done.
One possible plotline could be that they leave to escape the chaos in the wizarding world of Britain. Maybe they are seeking a fresh start in America where they can explore new magical cultures. For example, they could be interested in learning about the different types of magic practiced by American wizards and witches, like the use of wands that are made from different materials compared to those in Britain.
A plotline might involve Sakura facing a lot of judgment from the village. But she stands strong and raises the child with the help of her friends like Naruto and Ino. They support her emotionally and sometimes even materially. As for Sasuke, he might be on a journey of self - discovery and when he hears about the pregnancy, he has to decide whether his path still lies away from Konoha and his family or if he should change his ways.
One possible plotline could be that Harry discovers a plot against Snape before it's too late. Maybe he overhears some Death Eaters planning to ambush Snape while he's on a solitary mission. Harry then uses his invisibility cloak and magic skills he's learned over the years to outwit the Death Eaters and save Snape. This would show Harry's growth as a wizard and his ability to set aside past differences with Snape.
A plot could involve Snape's deaging being the result of a dark magic experiment gone wrong. Harry and Ginny initially suspect foul play but soon realize that Snape is truly a child in mind and body. They decide to protect him from those who might want to use his situation for their own gains. As they do so, Snape begins to form a bond with them, especially with Ginny, who he sees as a sister - like figure. Harry, meanwhile, has to deal with his own mixed feelings towards this new Snape, as he is constantly reminded of the old, often - hated Snape, yet also sees the potential for a new beginning.
One possible plotline could be that Harry travels back in time. In this scenario, he stumbles upon a young Severus Snape being bullied by some older kids. Harry, with his knowledge of Snape's future importance and his own sense of justice, steps in to save Snape. This could then lead to a change in their relationship dynamic. Instead of the animosity that exists in the original story, Snape might view Harry in a different light from the start, which could potentially change the whole course of events at Hogwarts in the future.
A possible plotline could be centered around Severus seeking help from unexpected sources. Maybe he turns to some of the more neutral or even good - aligned wizards and witches for advice or assistance, since he can't rely on Voldemort or the Death Eaters completely. The pregnancy could also be a catalyst for Severus to re - evaluate his life and his actions. He might start to question his past decisions and try to find a way to create a better future for himself and the unborn child, all while dealing with the stigma and danger associated with such a situation in the wizarding world which is full of secrets and power struggles.
One possible plotline could be that Naruto discovers some long - lost secret about his mother Kushina and decides to leave the village with her to explore this mystery further. Maybe they are on a quest to find some hidden power or knowledge that is related to Kushina's Uzumaki heritage.