The sims 3 sex mod. The game's normal pregnant scoring is used, so those base chances may be modified by a sim's traits or lifetime wish etc.
And must be turned on manually in the setting if you want that features.
Real One, Real Two and Heavy, for both gender.
Save the game, then reload it and the interactions will appear.
Updates July, Version 2.
If you have never used mods for The Sim 3 before, go over to the Mod The Sims site and follow the steps in this guide or this more detailed guide to set up your game properly.
This also affects oral sex, since a sim's mouth may not open properly or tongue may not extend.
Next, re-read the How To Use instructions.