Motherhusks increase both your libido and fertility speed percentage without changing the body. If you don't have the incubator perk, the highest you can go is 700% fertility speed increase, and it can get your libido to pretty near max or to max, depending on how high it is when you start. What I'm wanting to know is how to decrease it without making drastic changes...
Edit: If you've gone the Lacquine route, your fertility speed percentage can be as high as 1100% with motherhusks and incubator. At least, that's what one of my games is at. If it's possible to go higher I don't know, as I haven't done it.