Down syndrome screening is something that pregnant women generally know about, and it is also necessary to do in order to check if the fetus has any other problems. It is necessary to do Down syndrome screening, but what about non-invasive DNA? What does non-invasive DNA come from? Let's take a look at the difference between Down syndrome screening and non-invasive DNA testing together!
Down syndrome screening
By extracting the serum of the mother, the concentrations of alpha fetoprotein (AFP), human chorionic gonadotropin (β - hCG), and free estriol (uE3) in the maternal serum were detected; The risk factor for giving birth to a fetus with congenital defects should be calculated based on factors such as due date, weight, age, and gestational age at the time of blood collection;
Applicable gestational weeks: 14-20 weeks+6 days of pregnancy
① Advantages: affordable, safe and convenient, essential items for pregnancy testing, non-invasive.
② Disadvantages: Low detection rate and accuracy, high false positive rate. Tang screened high-risk individuals, and a large proportion of them were not diagnosed in the end.
Non invasive DNA testing
By collecting 10mL of peripheral blood from pregnant women, extracting free DNA, and using next-generation high-throughput sequencing technology combined with bioinformatics analysis, the risk of fetal chromosomal aneuploidy, namely trisomy 21 syndrome, trisomy 18 syndrome, and trisomy 13 syndrome, can be accurately determined.
Applicable gestational weeks: 12-26 weeks of pregnancy
① Advantages: Non invasive, high detection accuracy, low false positive rate.
② Disadvantages: High cost, narrow detection range, inability to detect chromosomal abnormalities in twins and chimeras, but non-invasive detection covers common chromosomal aneuploid diseases.
Amniocentesis
Amniotic fluid aspiration is one of the diagnostic methods used to further confirm the risk of Down syndrome in fetuses, based on the results of the Down syndrome screening. Under the guidance of ultrasound, a slender needle is inserted through the mother's belly, through the uterine wall, into the amniotic fluid cavity, and amniotic fluid is extracted for comprehensive examination; Mothers diagnosed with high-risk Down syndrome need to undergo amniocentesis.
Applicable gestational weeks: 16-22 weeks+6 days of pregnancy
① Advantages: It can detect 46 chromosomes at once, perform gene chip and single gene disease detection, and has high accuracy. It is currently one of the most widely tested and accurate prenatal diagnostic technologies.
② Disadvantages: There is a certain risk, intrauterine infection, and blood contact between mother and baby. Due to the 0.5% chance of miscarriage caused by this test, it is generally not recommended for mothers to choose this test.
The difference between Down syndrome screening and non-invasive DNA testing is believed to be understood by reading the previous article. If many people feel that there is no difference between the two, then they need to further study and research it. In addition, we have also introduced the methods of adhering to amniocentesis, and we can also understand what it is.
