I have already seen many mods in different flavors on MTS and other sites on the Internet that make WooHoo between 2 sims not 100% safe. They often come in different flavors allowing different percent chances of a risky WooHoo (or unplanned pregnancy) even if the player chooses to WooHoo only and not try for a baby. They also are most likely to be a core mod.
What if there was a limited way you could manage risky woohoo in the Sims 3? Like for individual sims, for example. In real life, men can opt for a kind of surgery called a vasectomy to permanently prevent them impregnating a woman. On the flip side, women can have their tubes tied, which works for them just as well as the male procedure.
So, what if there was a mod that allowed you to send individual sims to the hospital to have birth control surgery? They would just go straight to the hospital, go in and have the surgery (with a wait and a progress bar), and come out unable to have children at all, which means the option to 'Try for Baby' will no longer appear in the menu when this sim can woohoo and this also would completely disable risky woohoo, but only for that one individual sim. Once this procedure is complete, it becomes impossible for that sim to become pregnant or impregnate another sim, so long as you keep the mod installed in the game. If you remove it, the sim could lose their permanent birth control status.
Of course, in real life, this kind of surgery is not free, and it would be realistic to have to pay a price to have the surgery, of which this price could probably come in different flavors.

Also, I have heard in the news recently that in real life it may sometimes be possible to actually reverse a vasectomy! It is not always successful, but it works sometimes. Men may want to do this if the leave their SO and go to another and want to have children again. I don't think women have it as good as men, though. Once their tubes are tied, they can never ever have anymore kids as far as I know. So, optionally, it should also be possible to reverse permanent birth control in the game by having surgery again, and paying for it again, but like in real life this may not always be successful; different flavors could come in handy here, too.

Also, it would be nice if this did not have to be a core mod, but just a tuning mod, so it won't conflict with other core mods. If it has to be a core mod, then I would suggest it be implemented as part of an-already existing core mod. Perhaps J.M. Pescado could incorporate this into his Awesomemod, which is the core mod that I use in my game, and many others do, too.

Just food for thought...

BTW, I have World Adventures with the latest patches, but I think that this should work for both the base game and WA if at all possible.
