Awhile ago, I made myself a 2% risky woohoo mod. I was recently asked if I would release it. I have decided to do that but also added additional percentages. In the zip file you will find 2, 5, 10, 15, and 20 percent woohoo packages. Only use one at a time in your mods folder. This mod will conflict with any mod that alters woohoo. Also, this is a roll of the dice kind of mod. That means that even with the 20 percent that it may take awhile for your Sims to get pregnant.
Enjoy!