HCG is the chorionic gonadotropin secreted by the trophoblast after fertilization, and HCG stimulates the body to produce progesterone; both HCG and progesterone play a rather important role during pregnancy, and it is impossible to say which one is more important, but one is indispensable. The slow growth of HCG and its failure to double every other day is considered embryonic dysplasia, especially in the early stages of pregnancy when nature is superior and inferior to elimination, in which case a biochemical pregnancy or spontaneous abortion may occur. Progesterone is necessary for the maintenance of pregnancy. It relaxes the uterine muscle fibers, reduces uterine contractions, and facilitates the growth of the fertilized egg in the uterus. After all, the gestational sac is a foreign body to the uterus, and many people will experience rejection, and low progesterone can lead to pre-eclampsia or miscarriage. Poor progesterone means that the mother is unable to provide a good and balanced environment for the embryo to grow and develop, making it difficult for the fetus to grow and most of them stop developing in the first trimester, so it is important to observe closely. If you have low progesterone and normal blood HCG, you should take medication to protect the fetus under the guidance of doctor in time; if you have low progesterone and abnormal blood HCG, you should confirm the diagnosis of ectopic pregnancy or biochemical pregnancy at an early stage to avoid life-threatening and missed treatment, which will cause lifelong regret.