Down syndrome screening result is low risk

Down syndrome screening is very critical. If this screening is not done, there will be no way to fully understand the condition of the fetus in the womb. Once Down syndrome occurs, it will affect the physical health of the fetus. Therefore, only by completing the Down syndrome screening examination can you reduce the risk of developing this disease and ensure that the fetus in your womb is growing up healthily, so that you can give birth to the fetus.

The alpha-fetoprotein (AFP) generally ranges from 0.7 to 2.5 MOM (multiples of the median), and the higher the chorionic gonadotropin, the higher the chance that the fetus will have Down syndrome. In addition, the alpha-fetoprotein value, human chorionic gonadotropin value, and the pregnant woman's age, weight, and weeks of pregnancy can be entered into the computer, which will calculate the risk of the fetus developing Down syndrome. Different hospitals use different standards. If the probability indicated by the test result (such as 1/100) is greater than the normal reference value probability (such as 1/275), the result is positive, indicating that the fetus has a higher chance of being sick and further amniocentesis or chorionic villus sampling should be performed.

1. AFP (alpha-fetoprotein): AFP is a fetal-specific globulin with a molecular weight of 64,000 to 70,000 Daltons. It may have the immunoregulatory function of glycoprotein during pregnancy and can prevent the fetus from being rejected by the mother. AFP is synthesized by the yolk sac in the first 1 to 2 months of pregnancy, and then mainly by the fetal liver. A small amount of AFP can also be synthesized in the fetal digestive tract and enter the fetal blood circulation. The fetal blood AFP value increases rapidly at 6 weeks of gestation, reaches a peak at 13 weeks of gestation, and then gradually decreases as the pregnancy progresses to full term. The AFP in amniotic fluid mainly comes from fetal urine, and its change trend is similar to that of fetal blood AFP. Maternal blood AFP comes from amniotic fluid and fetal blood, but its change trend is not consistent with that of amniotic fluid and fetal blood.

2. In early pregnancy, the maternal blood AFP concentration is the lowest, and gradually increases as the pregnancy progresses, reaching a peak at 28-32 weeks of pregnancy, and then decreases. The serum AFP level of pregnant women carrying congenitally retarded fetuses is 70% of that of normal pregnant women, that is, the average MoM value is 0.7-0.8MoM.

3. FreehCGβ (free-β subunit-human chorionic gonadotropin): Pregnant women with congenitally retarded fetuses have a tonic increase in serum FreehCGβ levels, with an average MoM value of 2.3 to 2.4MoM. hCG is human chorionic gonadotropin synthesized by placental cells. It consists of two subunits, a- and b-, and is a ratio, that is, the marker detection value in the pregnant woman's body divided by the median value of a normal pregnant woman at the same gestational age. This value is MOM. Because the levels of prenatal screening substances vary greatly with increasing gestational age, their values ​​must be converted into multiples of the median (MOM) to make them "standardized" and facilitate clinical judgment.