How many weeks of pregnancy does hcg begin to drop?

The hcg value of pregnant women's weight is different at each stage of pregnancy. The hcg value will reach its peak in the early stages of pregnancy. By testing the hcg value, it can also effectively detect whether the baby has Down syndrome in the mother's belly. Generally, only when the hcg value reaches a certain height can it be proven to be related to Down syndrome. So when the pregnancy reaches the first few weeks, the hcg value will gradually decrease?

How many weeks into pregnancy will hcg begin to drop?

HCG usually reaches its peak in 8-10 weeks, starts to decline rapidly around 12 weeks, and remains stable from 18 to 20 weeks. Generally, an increase in the level of human chorionic gonadotropin to at least 2.5MoM is associated with Down syndrome. However, the actual average level of complete human chorionic gonadotropin in the maternal blood of DS patients is only 1.3MoM, which cannot clearly identify DS patients. The human chorionic gonadotropin-related molecules used for DS examination are free b-hCG and high sugar hCG (H-hCG).

Human chorionic gonadotropin is a glycoprotein secreted by trophoblast cells of the placenta and is composed of α and β dimers. Human chorionic gonadotropin (HCG) αβ is synthesized by syncytial trophoblasts. A glycoprotein hormone with a molecular weight of 36,700. The α subunit is basically similar to FSH (follicle stimulating hormone), LH (luteinizing hormone) and TSH (thyroid stimulating hormone) secreted by the pituitary gland, so they can cross-react with each other, while the structures of the β subunits are different. β-HCG is similar in structure to β-LH, but the last 24 amino acids are not present in β-LH.

The levels of human chorionic gonadotropin-related molecules are also related to the sex of the fetus. The levels of human chorionic gonadotropin in baby girls are significantly higher than those in baby boys. Complete human chorionic gonadotropin is produced entirely by the syncytiotrophoblast of the placental chorion. Human chorionic gonadotropin is produced by trophoblast transitional cells and syncytial cells. Human chorionic gonadotropin begins to be secreted 10-14 days after conception.

Function of hCG

1. It has the functions of FSH and LH, maintaining the life of the menstrual corpus luteum and enlarging the menstrual corpus luteum into the corpus luteum of pregnancy.

2. Promote the aromatization of androgens into estrogens and stimulate the formation of progesterone.

3. Inhibit the stimulation of plant lectins on lymphocytes. Human chorionic gonadotropin can be adsorbed on the surface of trophoblast cells to prevent embryonic trophoblast cells from being attacked by maternal lymphocytes.

4. LH-like function: before the fetal pituitary gland secretes LH, it stimulates the fetal testicles to secrete testosterone to promote male sexual differentiation. It can also promote the development of gonads, stimulate the activity of interstitial cells in the testicles in men, and increase the secretion of male hormones (testosterone). It is of great significance for the treatment of male patients with combined pituitary deficiency. It can not only promote gonadal development and the secretion of male hormones, but also promote the development of secondary sexual characteristics.

5. Pregnancy test. As an auxiliary means of early pregnancy detection, the working principle of pregnancy test is to detect the hCG value and determine whether the person being tested is pregnant by measuring the hCG content in urine or blood. After a normal woman becomes pregnant, the hCG level in her blood increases rapidly. 35-50 days after pregnancy, hCG can rise to greater than 2500 IU/L. It can reach 80,000 IU/L in 60-70 days. The hCG value reaches its peak at 60-80 days of pregnancy, then gradually decreases, reaching the lowest at 160-180 days of pregnancy, but is still significantly higher than normal, and then rises slightly and continues to maintain until delivery. In twin pregnancies, blood hCG levels more than double that of a single pregnancy.