Noninvasive DNA testing. What?
Non-invasive prenatal DNA testing is also called non-invasive prenatal DNA testing and non-invasive fetal chromosome aneuploidy testing. According to the Committee of American College of Obstetrics and Gynecology, an international authoritative academic organization, non-invasive prenatal examination is the most widely used technical name. Non-invasive DNA prenatal detection technology only needs to extract the venous blood of pregnant women, and use the new generation DNA sequencing technology to sequence the free DNA fragments (including fetal free DNA) in pregnant women's peripheral plasma, and analyze the biological information of the sequencing results to obtain the genetic information of the fetus, so as to detect whether the fetus has three major chromosome diseases.
Maternal plasma contains fetal free DNA, which provides a practical basis for this project. Fetal chromosome abnormality will bring slight changes in maternal DNA content, which can be detected by deep sequencing and biological information analysis, providing theoretical basis for the project.
Significance of prenatal detection in prevention and treatment of birth defects
China is a country with high incidence of birth defects. Among about160,000 newborns every year, children with congenital dementia account for 4%-6% of the total birth population every year, with a total of120,000, accounting for one fifth of the more than 5 million children with birth defects in the world every year. Our government pays about 8.2 billion yuan in medical and social relief for children with Down syndrome every year. Most of the surviving birth defects are lifelong disability or mental retardation, which cannot be cured, thus causing serious economic burden to society, and the psychological burden and mental pain caused to families cannot be measured by money. The clinical application of non-invasive DNA prenatal detection technology will make great contribution to the prenatal detection of birth defects in China.
Optimal time for non-invasive dna
Generally speaking, it is better to do non-invasive dna at 12-22 weeks, because the baby's DNA concentration in the blood is not early enough, and once the result is positive, it is impossible to confirm the follow-up sheep puncture (sheep puncture is suitable for 12-24 weeks, amniotic fluid cells are too old, so it is only necessary to do dangerous cord blood puncture to take live cells for confirmation), and it is recommended to induce labor at the latest 28 weeks, later than 28 weeks.
In addition, in the following cases during pregnancy, you can also start to consider doing non-invasive DNA prenatal testing: 1, "Tang sieve" or imaging screening, such as B-ultrasound during pregnancy, abnormal display or increased fetal NT value. 2, found that the single index value changes. 3. Placenta previa, low placenta, oligohydramnios or threatened abortion are no longer suitable for invasive prenatal examination. 4. Amniocentesis failed. 5. Psychological barriers of invasive prenatal examination.
Does non-invasive prenatal genetic testing require fasting?
No, regular diet will not affect the test results. After the consultation, Ms. Liu thought about it and finally decided to do non-invasive prenatal genetic testing. Although there are fewer types of examination than amniocentesis, at least it does not harm the mother. After 3 weeks, the test result is low risk, that is to say, the fetus can be ruled out with 2 1- trisomy syndrome, 18- trisomy syndrome and 13- trisomy syndrome with 99% certainty. Ms. Liu finally breathed a sigh of relief. Through the follow-up obstetric examination, the baby was all right. As a more accurate screening method for Down syndrome, the new non-invasive prenatal genetic testing technology has brought more choices to expectant mothers in need.
The adaptive population includes: pregnant women with critical risk of Down's screening for 2 1- trisomy or 18- trisomy syndrome, and pregnant women with invasive prenatal diagnosis contraindications (such as active infection, central placenta previa, threatened abortion, etc.). ), pregnant women who have missed the serological screening time, etc. However, the types of chromosomal abnormalities diagnosed by this technique are still limited, and not all chromosomal abnormalities can be found. In short, due to the limitations of non-invasive gene prenatal testing, it needs careful consideration and consultation. Doctors will need to make personalized prenatal screening and prenatal diagnosis programs according to the specific situation of pregnant women.