One common trope is the 'fish - out - of - water' situation for both characters. Castiel, being an angel, is not used to the concept of human pregnancy, and Dean has to deal with a very non - traditional male pregnancy. Another trope is the over - protective Castiel, like in many stories where he goes to great lengths to keep Dean safe during the pregnancy.
The 'secret - keeping' trope is also quite common. Dean might be hesitant to tell others in the Supernatural world about his condition, fearing their reactions. And there's often the trope of the 'unexpected bond' that forms between them during this time, strengthening their relationship in ways they didn't expect, as seen in stories like 'The Unforeseen Bond' where they discover new aspects of their feelings for each other.
Many fanfictions use the trope of 'supernatural complications'. Since they are in the Supernatural universe, there could be other forces that either try to harm Dean because of the pregnancy or are interested in the unborn child for their own purposes. This adds an element of danger and adventure to the story, like in 'Perilous Pregnancy' where they have to fight off demons who want to use the baby for dark magic.
Chapter 311, "Signed Jiang Yan", is the clearest early answer because it turns Seeing Shen Lan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Shen Lan knocked on the door before entering when Jiang Li was...
Chapter 318, "I Shouldn't Have Given Birth to You in the First Place!", is the clearest early answer because it turns Aunt Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Cheng glanced at the pink and white building from the bus.
Chapter 266, "He Really Deserves to Die!", is the clearest early answer because it turns Director Sun Suspected's situation into a concrete plot event. It opens with Upon hearing this, the deputy director's expression also turned...
Chapter 496, "Hot Pot Tonight!", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event. Early on, This woman is way too fierce, yelling at our Wenwen like that.".... By the end, Jiang Li gathered them up, found a flat stone, and began to rub them....
Chapter 583, "Making a Fool of those Big Shots!", is the clearest early answer because it turns Zhou Xu's situation into a concrete plot event. Early on, Days before, Jiang Li had predicted that today would bring a great.... By the end, You can play the game this way?!.
Chapter 553, "His Love Runs Deep", is the clearest early answer because it turns Chen Manman's situation into a concrete plot event. Early on, His gaze shifted to Luo Xuan's empty hands, and Ai Xiaochun's.... By the end, We could use this to our advantage..
Chapter 493, "Affinity Only 50 Now?!", is the clearest early answer because it turns Brother Shaojing's situation into a concrete plot event. The chapter gives readers a real answer by opening on You!" Shang Shaojing was so annoyed he gritted his teeth, "Jiang Yan,...
Chapter 321, ""Great Benefactor" is Jiang Li?!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Several people thus settled down in the living room, and the servants...
Chapter 589, "Green Tea! Green Tea! Damn Green Tea!", is the clearest early answer because it turns Yu Li's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Thinking of this, Zhao Lang gave a slight smile, "Alright, pedaling...
Chapter 392, "Connected to Shang Shaobai", is the clearest early answer because it turns Connected's situation into a concrete plot event. Early on, Bai Lu's hopeful heart had sunk once again.. By the end, Why not give it one more try?.