There is also the option of "Escape from the giant Insect Lab"
3d game. Clothes are removable. And bugs are everywhere. The character will get pregnant if a bug finishes it animation. Belly will grow slowly but surely. Game is rather short with only 3 levels and 2 bug types.
Invertebrates in general, and prominant oviposition/impregnation themes would be great. Like Parasite Infection, the sewer level of Parasite in City, or the parasite nest in Cursed Armor.
I've also played Slugs and Bugs, but too wordy, brain hurty.
EDIT: Also, nipple fucking would be godly