HCG, also known as human chorionic gonadotrophin, is a glycoprotein secreted by placental trophoblast cells. After fertilization, HCG can enter the mother's blood and rapidly increase in value until the 8th to 10th week of gestation, and then slowly decrease in concentration until it reaches a stable level at the 18th to 20th week.

　　How is HCG produced? As the fertilized egg lays, it stretches out its dendritic tentacles, which are called hairs, and grabs onto the wall of the uterus, where it forms an early placenta. Before the placenta matures, the hairs become thick and attach to a thin membrane. These chorionic membranes are gradually filled with blood vessels, which form the primary link between the mother and the embryo, metabolizing waste. The growth of this villi is what we call a doubling, with HCG levels roughly doubling every 2.2±0.5 days during the first 3 months of pregnancy. The absolute value of serum HCG varies greatly between different periods of pregnancy and between pregnant women, and there is no comparability between them, only their own comparison can be made. So you don't have to compare yourself to others, as long as your HCG increases normally. However, if the reexamination of HCG is still not doubled or doubling is not good, biochemical pregnancy or ectopic pregnancy should be considered. Ectopic pregnancy is usually accompanied by obvious symptoms, such as low progesterone, abdominal pain, bleeding, etc. You should see a doctor.

　　Another very important function of HCG is to reduce the rejection reaction of pregnant women. You have a parasite on you, and in general, your immune system is going to attack, but HCG is confusing the mother, telling her it's safe, it's your own, so your immune system doesn't fire. The synergistic effect of HCG and progesterone, on the one hand, enables the embryo to obtain nutrients, on the other hand, guarantees the safety of the embryo, so neither is indispensable. The doubling of HCG is not good. Because of the lack of nutrients in the embryo, it may be stunted or even stop breeding. Without enough progesterone, the embryo may become unstable, causing bleeding and even miscarriage. However, the low value of HCG and progesterone does not mean that the abortion will be inevitable, but the probability will be high. Once there is bleeding, you should go for a check. If you have a bad pregnancy history, you can monitor it just in case.