Progesterone in early pregnancy is sometimes not very stable, but as long as the blood progesterone check is above 25ng/mL, that is the normal range. If the progesterone is below 6ng/ml, then the pregnancy is not successful, which means that the progesterone is too low. If the progesterone is below 20ng/ml, then if you have vaginal bleeding, you need to apply progesterone to preserve the pregnancy. Because there are many reasons for vaginal bleeding, it is not certain whether it is caused by low progesterone or not. If the progesterone is lowered in the blood test, then progesterone can be used to preserve the fetus because it replenishes progesterone on the one hand and relieves the spasm of smooth muscle on the other hand, so it plays a role in preserving the fetus.