Is non-invasive DNA better or amniocentesis better?

Non-invasive DNA is mainly used to detect chromosomal abnormalities. It can also detect some related complications and make good diagnosis. It is also a common way to detect gene chromosomes. Amniocentesis is for diagnosing the sex of the fetus. It can also check whether there are skeletal and visceral functions or organ malformations. These are all for the purpose of conducting corresponding examinations for groups with genetic diseases in their families.

Non-invasive DNA

There are many ways to detect chromosomal abnormalities in the developing fetus, including non-invasive DNA prenatal testing, also known as non-invasive prenatal DNA testing and non-invasive fetal chromosomal aneuploidy testing. According to the American College of Obstetricians and Gynecologists Committee, an internationally recognized academic organization [1], non-invasive prenatal DNA testing is the name of the most widely used technology.

The non-invasive DNA prenatal testing technology only requires the collection of venous blood from pregnant women, and the use of new-generation DNA sequencing technology to sequence the free DNA fragments (including fetal free DNA) in the maternal peripheral plasma. The sequencing results are then subjected to bioinformatics analysis to obtain the genetic information of the fetus, thereby detecting whether the fetus suffers from the three major chromosomal diseases of trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome).

Amniocentesis symptoms and signs

Gender identification is usually done by drawing 12 ml of blood from the pregnant woman before birth and testing and analyzing the fetal DNA chromosomes that are free in the mother's body to identify the gender of the fetus. Gender identification is prohibited in our country, and only Hong Kong can do fetal gender identification. The main identification agencies in Hong Kong include Hong Kong Antenatal Consultant Centre, Zentroge, etc.

The best time to do amniocentesis is between 16 and 20 weeks of gestation, usually for pregnant women aged 35 or above. During the procedure, a needle is inserted into your amniotic fluid under the guidance of a level 2 B-ultrasound to draw out some amniotic fluid, which is then taken out and placed in the laboratory for chromosome culture for about a week to determine whether the baby has any deformities, including cleft lip and congenital diseases. The gender can also be determined.

This experiment is risky, but the accuracy rate is over 99%. The accuracy of Down syndrome screening is about 70%, and it is usually performed between 15 and 20 weeks of pregnancy. The best time to do an ultrasound is at 18 weeks, which can detect bone and visceral deformities including cleft lip, and can also determine the baby's gender.

Medication

1. For pregnant women in the appropriate period of pregnancy, use B-ultrasound to determine the abdominal puncture point (where there is a lot of amniotic fluid and no fetal limbs), or perform puncture under B-ultrasound monitoring;

2. Before puncturing the amniotic fluid, the pregnant woman can lie in bed and turn over five times in a row to suspend the fetal cells in the amniotic fluid in the uterus, making it easier to puncture and extract more fetal cells.

3. Use the puncture kit to disinfect the puncture site according to aseptic requirements, spread the hole towel, puncture with the puncture needle, slowly extract 10-20 ml of amniotic fluid, slowly inject it into the sterile centrifuge tube along the tube wall, and seal it with a sterile seal;

4. Centrifuge conventionally, open the seal under sterile conditions, discard the supernatant, keep about 1 ml of amniotic fluid and mix the cell sediment into a cell suspension for genetic testing or cell culture;

5. Pour 1 ml of the cell suspension used for genetic testing into the prepared 1.5 ml sterile sealed plastic centrifuge bottle; seal it together with the detailed test records of the pregnant woman, put it in an ice pack and send it to the testing unit (or send it by express mail). The testing unit will keep the file after receiving it and perform genetic testing (chargeable item).

6. For cell culture, evenly distribute the suspension into the prepared culture bottles, seal them aseptically and place them in a CO2 incubator for culture. Observe the growth with an inverted microscope every few days and replace part of the culture medium as needed. After culturing for 15-20 days, when the cells cover the wall of the bottle, harvest the cells for chromosome analysis.