There might be such a fanfic, but it's difficult to say for certain. Fanfic writers come up with all sorts of creative and often complex storylines. However, these specific elements of Daenerys being pregnant and Varys poisoning someone might be a rather unique and perhaps not overly common combination in the world of fanfics. It could be that a writer has explored this idea for the sake of creating a new and unexpected plot twist.
One possible plot could be that Daenerys' pregnancy is a cause for political unrest. Varys, being poisoned, might have some knowledge about who is behind it. Maybe he was poisoned by someone who wants to use Daenerys' unborn child as a pawn in the power struggle. His death could then set off a chain of events where Daenerys has to fight even harder to protect her child and her claim to the throne, all while trying to figure out who killed Varys.
I'm not sure if there is a specific fanfic exactly about that. There are a vast number of 'Game of Thrones' fanfics out there, and while the themes of Daenerys' potential pregnancy and Varys' fate (including being poisoned in some storylines) are common elements, it would be difficult to say for certain without a more in - depth search. You could try searching on fanfic - specific websites like Archive of Our Own or FanFiction.net using relevant keywords.
One possible plot could be that Varys poisons someone who he believes is a threat to Daenerys's unborn child. He might be acting out of loyalty to Daenerys and her future reign. Maybe he poisons a political rival who has been spreading rumors about the paternity of the child or planning some sort of harm to Daenerys during her pregnancy.
There were two possible reasons Ku He wanted to kill Xiao En. The first possibility was that Xiao En knew Ku He's unspeakable secret. Back then, Ku He was so hungry that he wanted to feed on humans, and Xiao En had witnessed that scene with his own eyes. In order to protect his reputation, Ku He did not want Xiao En to reveal this secret, so he decided to kill Xiao En. The second possibility was that Xiao En and Ku He had saved Ye Qingmei together, so Xiao En knew the secret of the temple. Ku He wanted to keep the secret of the temple and did not want anyone to know. He was afraid that Xiao En would leak it, so he decided to kill Xiao En.
There were two possible reasons Ku He wanted to kill Xiao En. The first possibility was that Xiao En knew Ku He's unspeakable secret. Back then, Ku He was so hungry that he wanted to feed on humans, and Xiao En had witnessed that scene with his own eyes. In order to protect his reputation, Ku He did not want Xiao En to reveal this secret, so he decided to kill Xiao En. The second possibility was that Xiao En knew the secret of the temple because he and Ku He had rescued Ye Qingmei and knew the location of the temple. Ku He wanted to keep the secret of the temple and did not want anyone to know, so he wanted to kill Xiao En. However, the specific reason why Ku He wanted to kill Xiao En was not explicitly mentioned in the search results provided.
Well, it could be that Varys thought Dany was becoming too much like the tyrants she opposed. So he tried to take actions against her. Dany, being a powerful and often ruthless character in these stories, wouldn't tolerate such betrayal and thus killed Varys. For example, if Varys was spreading rumors about Dany's sanity or her ability to rule, Dany would see him as a direct threat to her claim to the Iron Throne.
The reason Wu Zhu killed Lin Gong was to help Fan Xian take revenge. Fan Xian wanted to kill Lin Gong, but because Lin Gong was Lin Wan 'er's brother, Fan Xian couldn't do anything to him. Thus, Wu Zhu decided to kill Lin Gong for Fan Xian. Lin Gong did not agree to his sister marrying Fan Xian. He thought Fan Xian was a sloppy person and was not suitable for his sister. For this reason, Lin Gong had always been dissatisfied with Fan Xian and opposed him in every way. In the end, Lin Gong sent people to assassinate Fan Xian. In the end, they did not kill Fan Xian. Instead, they killed Fan Xian's good friend, Teng Zijing. Fan Xian was angry at Wu Zhu for killing Lin Gong because Wu Zhu had made the decision for him without authorization. He had knocked Fan Xian out and killed Lin Gong himself. Fan Xian felt that this kind of arbitrary logic was unreasonable and also despised the existence of life. Wu Zhu thought this kind of killing logic was natural, but Fan Xian could not accept it. Fan Xian believed that Wu Zhu should not decide for him whether to kill his enemy. Therefore, Fan Xian was angry at Wu Zhu.
The reason Ye Qingmei killed the prince was to help the Qing Emperor ascend the throne. She thought that killing the two princes could prevent them from causing more trouble to the people. Ye Qingmei's ability and influence made the Qing Emperor and Empress Dowager feel fear because she had established a powerful Chamber of Commerce, held the power of the palace treasury, and advocated the social ideals of fairness and equality. The Qing Emperor chose to kill Ye Qingmei because her social ideals would harm his interests. The Qing Emperor could not tolerate her existence. Ye Qingmei's death was due to her conflict with the Qing Emperor and her challenge to feudal society.
The reason why Wu Zhu wanted to kill Fan Xian was to protect him. In " Celebrating Years," Fan Xian was threatened with an assassination. Lin Gong was the mastermind behind the assassination. In order to protect Fan Xian and resolve the misunderstanding between them, Wu Zhu decided to help Fan Xian get rid of Lin Gong. In addition, Fan Xian liked Lin Wan 'er, and Lin Gong was Lin Wan' er's brother. If Fan Xian killed Lin Gong, his relationship with Lin Wan 'er would break. Wu Zhu didn't want to see Fan Xian and Lin Wan 'er separated, so he chose to personally kill Lin Gong to protect Fan Xian.