Why is there a critical risk in Down syndrome screening?

Pregnant women should take every prenatal checkup seriously. Checkups during pregnancy will help them understand their physical condition and the development of the fetus. The development of the fetus is always a concern for pregnant women. Pregnant women can undergo Down syndrome screening when they are 15 weeks pregnant. Now more and more people are aware of the importance of Down syndrome screening and will pay special attention to this examination and will actively undergo it.

Why is Down syndrome screening a critical risk?

Down syndrome screening is generally performed by testing the concentrations of alpha-fetoprotein, chorionic gonadotropin and free estriol in the pregnant woman's serum to determine whether the fetus has Down syndrome, that is, to determine the risk factor of the fetus for congenital idiocy or neural tube defects. The critical risk of Down syndrome screening is a borderline risk, which means that there is a certain chance of getting the disease, but it does not mean that the fetus will definitely have Down syndrome. Therefore, if the Down syndrome screening is a critical risk, amniocentesis will be recommended to further determine the development of the fetus.

Why do we need Down syndrome screening?

Not all pregnant women will not suffer from Down syndrome if they do not have a family history of Down syndrome. So far, there is no medical cure for Down syndrome. Therefore, measures to control the occurrence of Down syndrome mainly focus on preventing or reducing the birth of children with the disease. But one thing that needs to be made clear is that the purpose of screening is not to diagnose a certain disease, but to screen out people who are more likely to have a certain disease. Down syndrome screening is aimed at specific people who do not have any corresponding disease indicators (such as all pregnant women). Through examination, high-risk groups with a higher possibility of Down syndrome are screened out for subsequent diagnostic examinations.

Is the critical risk of Down syndrome screening more serious than the low risk?

1. Generally speaking, when doing Down syndrome screening, you must not eat or drink anything after 12 o'clock the night before the test, and come to the hospital for the test on an empty stomach the next morning (fasting is not required). In addition, the examination is also related to the menstrual cycle, weight, height, accurate gestational age, and fetal age. It is best to consult a doctor for other preparations before the examination.

2. The screening includes drawing venous blood from pregnant women, as well as ultrasound indicators such as NT (thickness of the nuchal translucent membrane) or alpha-fetoprotein (AFP), human chorionic gonadotropin (HCG), free estriol (uE3) and inhibin A (inhibin A) (four mid-term items), combined with the expected date of delivery, weight, age and gestational age of the pregnant woman at the time of blood sampling, to calculate the risk factor of "Down syndrome baby". In this way, when the false positive rate is 5%, more than 80% of Down syndrome babies can be detected.

3. In the detection of multiple indicators of maternal serum prenatal screening, radioimmunoassay, enzyme immunoassay, time-resolved immunofluorescence and chemiluminescence methods are generally used. Due to the large variation in the results of radioimmunoassay and enzyme immunoassay, time-resolved immunofluorescence and chemiluminescence methods are generally used at present, and the country recommends time-resolved immunofluorescence.