I'm not sure that the traits a sim has make much of a difference whether a sim gets pregnant or not with Try for Baby. Try for Baby does not always cause a pregnancy every time. The default pregnancy chance setting is 80% so you just might have been unlucky with the two sims involved and it just might take trying several times or more. But I do know that sims with those traits can get pregnant or cause a pregnancy as I have sims with those traits that have had kids in my main save.
The negative hit on romance does come from the traits and I think it's from the Hates Children trait. Non Committal sims just usually give you trouble when asking to marry as they will turn down proposals a lot.
Hope this helps.
Sorry, forgot about the trait changes. Those 2 are mentioned in the patch notes as having been changed. I've had babies since the traits change but will have to check to see if any of their parents had those traits. Mostly though, I was speaking about what happened in my save before that patch. I will need to test a bit to see what happens now.
