Rockstar- I stopped mine abruptly at 10 weeks, just the other day. I would hope my clinic wouldn't have put me at risk of loosing this pregnancy by having me stop when they did. I'm assuming everything is fine, still am nauseous, no cramping, no spotting. The placenta starts making progesterone at 10 weeks, although I've even seen some sources say as early as 8 weeks. I think stopping at 12 weeks is being very cautious because the placenta will have already been making it for two weeks. I understand your fears though. I was scared to stop taking it with my first pregnancy at 5 weeks even though the clinic assured me my body didn't need the extra support. I don't feel scared this time, just relieved to be done.