A normal HCG doubling indicates that the embryo is developing well. If the progesterone is low, there may be symptoms of pre-eclampsia, which is due to the high fluctuation of progesterone in the early stages of pregnancy. Normally, if it is within the normal range, progesterone is not a problem. If progesterone is lower than normal, generally patients may have symptoms of preterm abortion, such as a small amount of vaginal bleeding or stomach pain, in this case, attention must be paid to bed rest as much as possible and reduce activities. If progesterone is lower than 5ng/ml, this condition should be considered as poor embryonic development. Therefore, if you find that your progesterone is low and your HCG is normal, you should continue to observe, and if you have the conditions, you can go for ultrasound to check if the fetus is developing normally.