I also think this might have something to do with the rating of the game, but I would love it if there was an option. Or better yet, if there was a way for me to set the risk, from 0% to 100% for both woohoo and try for baby (I hate the 80% chance with try for a baby, where is the sport in that?).
I do have the above mentioned MCCC, and would say that if you only ever use one mod, that would be it. It can seem a bit daunting, because it can do SO much, but just take it one step at the time and use only what you want to use.
Personally I play with both woohoo and try for baby set to 11% at the moment and still have families with 4-5 kids (but some who has tried and tried but not gotten any). I play historical, so when birth controls come onto the market and knowledge about fertility and ovulation increases I intend to lower the risky woohoo and raise the try for a baby so they are different.