What does the mid-term Down syndrome screening mainly check?

Because most people are now very panic about some physical changes, so everyone starts to pay more attention to some physical reactions, such as mid-term Down syndrome screening. The main purpose of Down syndrome screening is to see if you have Down syndrome, or whether there is a possibility of this risk. Some types of Down syndrome screening tests are necessary to ensure safety. Another is to check whether the baby has some congenital diseases.

Early Down syndrome examination time: 11-14 weeks; B-ultrasound examination to see the thickness of the baby's nuchal translucency, which needs to be combined with the blood test results. The accuracy is relatively high, up to 90%.

Mid-term Down syndrome examination time: 16-18 weeks; blood test, Down syndrome screening is a detection method that extracts the serum of the pregnant woman, detects the concentration of alpha-fetoprotein and chorionic gonadotropin in the maternal serum, and calculates the risk factor of giving birth to a child with Down syndrome based on the pregnant woman's expected date of delivery, age, weight and gestational age at the time of blood collection. The accuracy is lower than that of the early Tang Dynasty, 60-70%.

However, both early and mid-stage Down syndrome tests have certain false positive and false negative rates. For the safety of the baby, it is best to do both.

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Down syndrome screening is mainly for screening Down syndrome, that is, to check whether the baby will be a congenitally stupid Down syndrome baby, mainly checking alpha-fetoprotein, human chorionic gonadotropin, and free estriol.

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 occurs in older pregnant women, while the other 80% of Down syndrome fetuses 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: all young pregnant women undergo Down syndrome screening tests, and those who are shown to be at high risk will 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.