Is non-invasive testing accurate at 13 weeks?

Every pregnant woman should have accurate control of her pregnancy time so that she can undergo different maternal examinations at each stage of pregnancy to determine the growth of the fetus in the belly and any corresponding problems that may exist. Pregnant women will be very familiar with non-invasive DNA because most pregnant women need to undergo non-invasive DNA screening. But if non-invasive DNA screening is performed at 13 weeks of pregnancy, are the test results accurate?

How many weeks does non-invasive DNA testing take?

According to the guidelines of the National Health and Family Planning Commission, the optimal time for non-invasive DNA testing is from 12 weeks of pregnancy to (22 weeks + 6 days). If the pregnancy time exceeds the upper limit (gestational age > 22 weeks + 6 days), the detection risk increases; if it is too short (gestational age < 12 weeks), it will also affect the accuracy of the screening results. Therefore, most pregnant women choose to do non-invasive DNA prenatal testing at 14-18 weeks of pregnancy.

In addition, if the following conditions occur during pregnancy, you can also consider non-invasive DNA prenatal testing:

1. "Down syndrome screening" or imaging screening, such as B-ultrasound during pregnancy, shows abnormalities or increased fetal NT value.

2. It is found that the value of a single indicator has changed.

3. Placenta previa, placenta low lying, oligohydramnios or threatened abortion are no longer suitable for invasive prenatal examinations.

4. Amniocentesis failed.

5. Have psychological barriers to invasive prenatal examinations.

Non-invasive DNA, that is, non-invasive genetic testing, non-invasive DNA prenatal testing, also known as non-invasive prenatal DNA testing (Noninvasive Prenatal Testing, NIPT), non-invasive fetal chromosome aneuploidy testing, etc. The most widely used technology internationally is called NIPT, which is defined by a committee of the American College of Obstetricians and Gynecologists.

Due to the limitations of the level of technological development, the current non-invasive DNA screening in China mainly focuses on the three most common chromosomal diseases, namely T21 chromosome abnormality (Down syndrome), T18 chromosome abnormality (Edwards syndrome) and T13 chromosome abnormality (Patau syndrome).

According to the "Technical Specifications for Prenatal Screening and Diagnosis by High-throughput Gene Sequencing (Trial)" issued by the National Health and Family Planning Commission (hereinafter referred to as the "Specifications"), non-invasive DNA is a method of prenatal screening and diagnosis using gene sequencing technology. It only requires collecting more than 5 ml of peripheral venous blood from pregnant women and extracting fetal free DNA fragments contained in maternal peripheral plasma. Through the new generation of high-throughput DNA sequencing and bioinformatics analysis, the genetic information of the fetus can be obtained and the risk of the fetus suffering from chromosomal aneuploidy can be detected.

Is non-invasive DNA accurate?

The accuracy rate of non-invasive DNA is still very high. According to incomplete statistics, the accuracy rate is about 99%. It mainly collects peripheral blood from pregnant women and can also extract fetal DNA. It uses DNA sequencing technology combined with biological analysis to calculate whether the child's chromosomes are aneuploid and whether he or she suffers from Down syndrome or Edwards syndrome. As long as it is possible to avoid the birth of the fetus and achieve good eugenics. The sensitivity and specificity are much higher than traditional serological tests, and the safety is also higher.