I think there's something inherently creepy about being turned on by pregnancy. I mean there's literally a kid in there. seriously.
how is that creepy? i dont get turned on by the kid... im turned on by the effect on the mother. her belly swelling up as her child is growing inside her. its the belly that i find attractive, and the concept of that its only going to get bigger. so you could say theres a bit of an inflation aspect in there too.
also impregnation as INH mentioned is hot too.
imo the flowing of bodily fluids between a husband and wife is the ultimate form of intimacy and loveuality, be it swallowing or whatever. and to me its the kinkiest thing i hope to enjoy someday in marriage. us guys like to mark our territory.