Down syndrome screening 18 trisomy critical risk

The development of medical technology is obvious to all of us. For example, the probability of a deformed child being born was much higher decades ago than it is now. An important reason for this phenomenon is that the medical level decades ago was still far behind that of today. Prenatal examinations at that time were not as comprehensive as they are now, and many pregnant women may not have undergone scientific Down syndrome screening tests. Down syndrome screening has a great relationship with deformity. What is the critical risk of trisomy 18 in Down syndrome screening?

Critical risk just means that the risk is relatively high, not necessarily that there is a problem. Further examination, such as non-invasive DNA or amniocentesis, is needed.

Down syndrome screening test is the abbreviation of prenatal screening test for Down syndrome. The purpose is to determine the risk of the fetus suffering from Down syndrome by testing the pregnant woman's blood. If the Down screening test results show that the fetus is at a higher risk of suffering from Down syndrome, further confirmatory tests should be carried out - amniocentesis or chorionic villus sampling.

Fetuses with Down syndrome are not exclusive to older pregnant women. Although older pregnant women over 35 years old are closely related to Down syndrome, the older the age, the greater the chance of giving birth to a child with Down syndrome. However, young women may also give birth to children with Down syndrome, and only 20% of Down syndrome

The syndrome occurs in older pregnant women, and the other 80% of Down syndrome babies are born to young pregnant women under 35 years old. Therefore, if only older pregnant women are examined, it will not be a good way to prevent Down syndrome.

On the other hand, if all pregnant women undergo amniocentesis or chorionic villus sampling, not only will the cost be higher, but it will also increase the chance of miscarriage, so it is not necessary for all women to undergo amniocentesis or chorionic villus sampling. Currently, the best way to prevent Down syndrome is that all young pregnant women undergo Down syndrome screening tests, and those who are shown to be at high risk undergo amniocentesis or chorionic villus sampling. Through amniocentesis or chorionic villus sampling, it can be determined whether the fetal chromosomes are normal and whether the fetus has Down syndrome.

Young pregnant women under the age of 34 should undergo Down syndrome screening, which can be performed between 15 and 20 weeks of pregnancy, and preferably between 16 and 18 weeks. Pregnant women who are over 34 years old, women with Down syndrome in their family, and women who have given birth to children with Down syndrome are already at high risk, so they do not need to undergo Down syndrome screening and should go directly to amniocentesis or chorionic villus sampling.

Currently, the Down syndrome screening test tests the concentration of alpha-fetoprotein (AFP) and human chorionic gonadotropin (β-hCG) in the pregnant woman's blood, and combines it with the pregnant woman's age to use a computer to accurately calculate the risk of each pregnant woman carrying a fetus with Down syndrome. The normal value of alpha-fetoprotein should be 0.4~2.5MoM. The lower the test value, the higher the chance that the fetus will suffer from Down syndrome. The higher the level of chorionic gonadotropin, the higher the chance that the fetus will have Down syndrome. In addition, the doctor will input the alpha-fetoprotein value, human chorionic gonadotropin value, as well as the pregnant woman's age, weight, and weeks of pregnancy into the computer, which will calculate the risk of the fetus developing Down syndrome. If the test results show that the risk is lower than 1/270, it means that the risk is relatively low and the chance of the fetus developing Down syndrome is less than 1%. However, if the risk is higher than 1/270, it means that the fetus is at high risk of disease and further amniocentesis or chorionic villus sampling should be performed.