(Usually dr's allow you to stop Prometrium
sometime around 12-14wks, as by that point your body should be making a higher level
than even the supplimental pill can give you... basically, by that point if your progesterone levels aren't high enough, there's nothing more a dr can do.)
I had 2 mc's back-to-back with low progestrone levels. When I got pg again, my dr immediately put me on Prometrium even before my blood results came back (which again were low!