I don't know. I mean, for me, it's a very specific thin--pregnant people giving birth. My obsession with birth started early. I recently found diaries I wrote in when I was only six years old, and I drew images of women giving birth. I've absolutely no idea where it comes from. Can anyone really, truly say where their kinks come from? I grew up Catholic, a relatively sheltered girl, and my parents never sat me down for the talk. I don't recall seeing anything, but I imagine I must have picked something up somewhere if I knew how babies came out. My being fascinated by birth pre-dated knowing things like how sex works and what periods are. But yeah, it's odd. It's the one thing guaranteed to get me off, imagining birth, and that's been the case for ages. I tend to like kinks that sort of go hand-in-hand with it--medical, sadism, embarrassment, control or lack of control over orgasms, etc...