The main distinction of porn with a story genre from regular porn is the presence of a coherent narrative. Regular porn often jumps straight to the sexual action, while the story genre tries to add some kind of story framework around it. But in the end, both are adult-oriented and feature explicit sexual content.
Well, it's hard to say for sure. The concept of 'porn-like' is quite subjective. Some might consider certain novels with excessive sexual descriptions as such, but it depends on individual perspectives and cultural standards.
In many places, 18+ porn comics are considered illegal. This is because they can have a negative impact on society and violate moral and legal standards.
In fanfics, all kinds of scenarios are possible. Just because it's written doesn't mean it adheres to the original canon. Maybe the author wanted to explore a unique relationship dynamic through this pregnancy plot. However, without reading it, it's hard to say more about it.
I don't know who Sam is without reading the 'kings fund sam's story'. Sam could be a patient, a researcher, a staff member or someone else related to the Kings Fund.