I think the idea is, that the utrogestan keeps the womb lining thin by continuing to break it down, (but without a bleed if that makes sense?) So, it acts a bit like a machine I guess, constantly churning over the lining and breaking down the bits to keep it well maintained.
If you were on a sequi regime and having periods, then you would get a nice timely bleed each month.
If that isn't how it works, I have no idea!
