Miscarriage,i.e.thretened/recu… spotting?

why is it that thousands of babies can be saved from a miscarriage by giving a women progesterone pesseries/suppositries in the first trimester.if spotting occurs and the pregnancy is thretened your body may not be able to sustain the right levels of progesterone which the baby needs to survive so levels start to drop.this can be caused by many things like a disablity or defect of the baby ,but it can just be a simple difficiantcy in progesterone.if you have recurrent miscarriage or start spotting insist on progesterone to sustain your pregnancy,dont be fobbed off as another statistic