Girl with an impregnation fetish gets knocked up - sets up family/friends
I'm honestly surprised I haven't found a story like this yet. Impregnation is a kink that many women have, and I've heard a lot of women talk about how happy they are when they're pregnant at the same time their friends/family are.
The story would follow a woman who has an impregnation kink - from sharing her fantasies to finally deciding to risk impregnation every time that she has sex. She might trick her boyfriend/causal sex partners, tell them what she wants, join a dare community centered around impregnation, or put herself in situations where she'd be almost helpless if someone decided to take her.
After she finds out she's pregnant, she keeps doing what she has before - wanting to keep getting off on one of her hottest kinks. But she doesn't reach that same high. She eventually either wishes she had someone to share pregnancy with and finds herself turned on by the idea of someone else also getting knocked up, or one day sees a friend/family member scantily clad/out of the shower/changing and thinks about how hot it would be for the other woman to get knocked up.
She then conspires to get the other girl(s) pregnant one way or another - inviting them to "risk" parties or dare groups, sabotaging birth control, telling their boyfriends to cum in them, or even drugging/restraining them. She might come to want to watch it happen.
If she's bi, she might seduce woman in order to get her naked & ready for a bare cock - might lie on top of her, pin her wrists down, and spread their legs apart so that he can walk into the room and enter her.