Snape would probably use his knowledge of potions. He might have brewed a special pain - relieving potion in advance. He would also use his Occlumency skills to try and block out some of the pain mentally. Since he is a strong - willed character, he would grit his teeth and endure it as best he could while focusing on the task at hand, which is giving birth safely.
One possible plot could be that Snape discovers he has a unique magical ability that allows him to carry a child. He might keep it a secret from everyone in Hogwarts due to fear of ridicule. As he nears the time of giving birth, he would have to find a secluded place within the castle or in the Forbidden Forest. He would endure the pain alone, using his own potions and magic to ease the process as much as possible.
One possibility is that in the fanfiction, she might be in a situation where she has cut herself off from her friends for some noble reason. Maybe she wants to protect them from some dark magic that she believes will target her during childbirth. Another reason could be that she's on a secret mission and has no choice but to be alone when she gives birth.
It could be that the father is an unknown wizard who Harry had a brief encounter with. Maybe it was a one - time magical connection that led to the pregnancy.
One possible plotline could be that Harry discovers he has a unique magical ability that allows him to give birth, and he has to go through the process alone in a secret place to protect his unborn child from dark forces. Another could be that he is magically cursed to give birth alone as part of a villain's revenge plot.
One possible scenario could be that Clary is in a situation where she has no one around due to some unforeseen circumstances like being stranded in an isolated place. Another could be that she chooses to be alone because she doesn't want others to see her in a vulnerable state during childbirth.
Maybe Simon. If the fanfic takes an alternate path where Clary and Simon end up in a romantic relationship, he could be the father. However, he might be away or unable to be with her when she gives birth.
One possible plot twist could be that Bella discovers a hidden power within herself during the birth. For example, she might be able to communicate with the baby in a telepathic way, which gives her the strength to endure the pain alone. Another twist could be that there are unexpected visitors who watch from a distance but choose not to interfere, adding an element of mystery to the story.
Bella might cope with the pain by focusing on her love for the baby. She could keep repeating positive thoughts about the future with her child in her mind, which helps her to block out the physical pain to some extent.
One possible plotline could be that Harry discovers he has a unique magical ability that allows him to give birth. He has to keep it a secret from his friends at first because he's not sure how they'll react. As the pregnancy progresses, he struggles with the physical changes and the fear of being alone. Another could be that some dark magic has been cast on him which results in this situation, and he has to find a way to reverse it while also dealing with the impending birth.