@fldly9t3l1d9 One relatively common cause of issues saving is using the BuyDebug cheat. It's fine to use it, but you'll need to disable it again (buydebug off) before saving.
If this isn't the problem, please run a simple test. Start a new save in Sunset Valley, pick an already-existing sim or household to play with, and see whether you can save. Then use MasterController to get the sim pregnant, or just do it the old-fashioned way; the point is to immediately trigger a pregnancy. (The MC command is Pollinate, under Basic, or Partner Pollinate, under Intermediate, if they have a partner you want to use. The latter requires the MC Cheats add-on.) Keep trying to save every eight sim-hours or so, after using Build/Buy, and let me know if and when it fails relative to the length of the pregnancy.
NRaas mods should be fine, as should CMarNYC's pregnancy controller. If you want to run the test with all of your existing content in place, that's fine, but if you have any trouble saving, try again with only NRaas mods and (optionally) the pregnancy controller.
I'd also be curious to know whether you could save your progress in one of your main saves after the baby is born.
