an update to the "normal" version of the stuck pregnancy bug:
i managed to catch a pregnancy the day it got stuck. i reloaded the game, and as the day played out, the birth happened as it was supposed to. one major thing was different between the stuck day and the day that didnt stick: an invasion.
there's a slight chance that it was interacting with a servant at exactly the wrong frame did it, but i think the problem is that an invasion prevented the birth dialog box from being created, which caused the birth to never process.
suggested hotfix: in the "upkeep loop" or whatever you've named it that increments the pregnancy timer, implement a check to se if days till birth is less than
zero, and force the dialog if so.