The blood test for early pregnancy is usually the result of a blood test for HCG, which is called human chorionic gonadotropin, a glycoprotein secreted by human trophoblast cells, and is usually secreted 2-3 days after fertilization of the egg, usually 8-10 days after fertilization, and can be tested in the blood for an elevated HCG level to indicate pregnancy. The exact value of HCG is usually different for each individual and the development of the gestational sac in the uterine cavity can be observed by the number of times the HCG is elevated. Usually, if the HCG doubles on the next day, it means that the embryo is developing very well, usually the HCG peaks at 8-10 weeks and then decreases rapidly.