There are some rather complex metrics that determine if Neighborhood Stories get triggered or not and for pregnancy and adoption it's related to the number of kids in your save (I think the relative amount compared to the total population).
So it could be possible that your save already has a bunch of kids (played and unplayed households) which could make it quite unlikely for new pregnancies and adoptions to get triggered.
You have made me sooooooo happy! It's fixed!!!!
What had happened was after I fully uninstalled my game, when I went to rebuild my families etc. It was working and then suddenly it wasn't. I had considered it might be after a certain number of Sims in general but not specifically children/toddlers/infants/babies. Your suggestion gave me a new direction that no one had previously mentioned. As I had been rebuilding families I did have an excessive amount of children and babies. Once I got it down to under 50, it worked!! I've since had 5 babies born through Neighborhood stories and I can't thank you enough for taking the time to write to me!!
