hcg changes during pregnancy

The hcg value is also an important data during pregnancy. This data can also show many changes. It is usually produced when sperm enters the female body, but its value is generally produced between the sixth day and the eighth week. It will change during this period. It will rise slowly at first and then slowly decrease. So what changes will occur in the hcg value during pregnancy?

Changes in blood hCG after pregnancy

hCG enters the mother's blood around the sixth day after fertilization and proliferates rapidly until the eighth week of pregnancy, then slowly decreases in concentration until the 18th to 20th week, then maintains for about 10 days and begins to decline (but still above normal levels). Generally, an increase in intact hCG levels to at least 2.5MoM is associated with Down syndrome. However, the actual average level of complete hCG in the maternal blood of DS patients is only 1.3MoM, which cannot clearly identify DS patients.

The hCG-related molecules used for DS examination are free b-hCG and high sugar hCG (H-hCG). H-hCG-related molecular screening for Down syndrome is sensitive and can be performed using urine sampling. The plasma H-hCG concentration in mothers of DS children was 9.9-fold higher than that in non-infected pregnant women.

Free b-hCG is the only known marker that can be used for both primary and secondary screening. The average level of free b-hCG in the blood of mothers with DS syndrome is 1.9MoM, while that in the blood of healthy mothers is 1.0MoM. The levels of hCG-related molecules are also related to the sex of the fetus, with hCG levels in baby girls being significantly higher than in baby boys.

Complete hCG is produced entirely by the syncytiotrophoblast of the placental chorion. Its main function is to stimulate the corpus luteum, which is beneficial to the continuous secretion of estrogen and progesterone, so as to promote the formation of uterine decidua and make the placenta grow and mature. It is now believed that hCG is produced by trophoblast transitional cells and syncytial cells. hCG begins to be secreted about 6 days after fertilization and reaches its peak around 60 to 70 days. It increases rapidly during the first 8 weeks of pregnancy to maintain the pregnancy. After about 8 weeks of pregnancy, hCG gradually decreases until it reaches relative stability around 20 weeks.

Precautions for hCG determination

1. Differentiate between normal and abnormal pregnancy: hCG changes during pregnancy present a bimodal curve. According to the normal hCG concentration changes, if the first hCG is within the normal range, 79% of people can have a full-term pregnancy. If the first hCG is lower than normal, 92% of pregnancies will fail.

2. Diagnosis and treatment of miscarriage: In incomplete miscarriage, there is still placental tissue remaining in the uterus, and hCG is qualitatively positive. In complete miscarriage or stillbirth, hCG may be negative. If hCG is below 2500U/L and gradually decreases, miscarriage or stillbirth is possible; when it drops to 600U/L, miscarriage is inevitable. If hCG in urine continues to decrease, it means that the fetus preservation is ineffective, otherwise it indicates that the fetus preservation is successful. Serum hCG should return to normal 4 days after delivery or 13 days after artificial abortion. If this situation is not met, the possibility of abnormality should be considered.

3. In cases of malignant hydatidiform mole, choriocarcinoma and male testicular teratoma, the urine hCG content is very high, reaching 100,000 to millions of international units.

4. Others: hCG changes vary during pregnancy toxemia and is often high; hCG levels increase during multiple pregnancies.