During the obstetric examination, the screening of fetal Down syndrome is common in the first trimester of Down's screening (9 to 13 weeks of pregnancy +6) and the second trimester of Down's screening (15 to 20 weeks of pregnancy +6). Serum, to detect the concentration of AFP, human chorionic gonadotropin (β-hCG) and free estriol (uE3) in maternal serum; it needs to be combined with the expected date of birth, body weight, age and gestational week when blood is collected, etc. , Calculate the risk factor for birth of a congenitally defective fetus.
There is also a new generation of high-throughput sequencing technology combined with biological information analysis to extract the fetal DNA free from maternal peripheral blood, that is, non-invasive DNA detection, to screen the fetus for the risk of chromosomal aneuploidy (down syndrome) Probability.
Before and after this inspection, I believe many mothers have such doubts:
I do n’t have a Down family member in my family or I have had normal children. Do I need to do a Downs screening for my baby?
My Tang screening results are critical or low-risk. I recommend non-invasive DNA testing. Is it really necessary?
I am an elderly pregnant woman, can I just do a non-invasive DNA test?
I heard that non-invasive DNA testing is more accurate than the results of Down's screening, is this true?
Well, there is no family history of Down syndrome
Is it certain that Tang's children will not be born?
It's not that there will be such patients in the family of both parents before they will give birth to Down's children. Every pregnant woman has the opportunity to have Down's children in every pregnancy. Because its pathogenesis is mainly the abnormal separation of chromosomes during ovulation and pregnancy, and the older the mother is, the higher the chance of the fetus suffering from the disease.
What is the difference between Down's screening and noninvasive DNA testing?
The principle of non-invasive DNA testing is to detect the DNA of the fetus in the maternal blood. In addition to the detection of 21-trisomy, 18-trisomy, and 13-trisomy, other chromosomal abnormalities of the fetus, such as abnormal number of other chromosomes And some chromosome deletion / duplication syndrome. Compared with traditional blood biochemical and ultrasound NT screening Down syndrome, the advantage of noninvasive fetal DNA testing is that the screening accuracy is higher.
Who needs to do non-invasive DNA testing?
Applicable population (1) Serological screening shows that pregnant women with common chromosomal aneuploidy risk values between high-risk cut values and 1/1000. (2) Those who have contraindications for interventional prenatal diagnosis (such as threatened abortion, fever, bleeding tendency, active period of chronic pathogen infection, Rh-negative blood type of pregnant women, etc.). (3) Those who are more than 20 + 6 weeks pregnant and miss the best time for serological screening, but are required to assess the risk of trisomy 21, trisomy 18, and trisomy 13
When pregnant women with the following conditions are used cautiously for testing, the test accuracy will be reduced to a certain extent, and the detection effect is not yet clear; or they should be recommended for prenatal diagnosis according to relevant regulations. include:
(1) High risk of prenatal screening during early and middle pregnancy. (B) 35 years old ≤ pre-birth age <40 years old, fear of amniocentesis. (3) Severe obesity (body mass index> 40). (4) Conception through in vitro fertilization-embryo transfer. (5) A history of fetal delivery with chromosomal abnormalities, except for couples with chromosomal abnormalities. (6) Twin pregnancy. (7) Other circumstances that the physician believes may affect the accuracy of the results.
Whether pregnant women are suitable for non-invasive DNA testing, you need to consult your obstetrician in detail according to their own conditions and conditions. Detection.