Is it better to do non-invasive DNA or amniocentesis?

Pregnant women should undergo Down syndrome screening during pregnancy. This is mainly to avoid the occurrence of Down syndrome children and reduce the incidence of congenital diseases. Therefore, for operations such as amniocentesis, you should choose a large hospital for examination when you are about to give birth, and you should do amniocentesis according to the doctor's advice. Non-invasive DNA is only used to extract fetal DNA for testing when the risk of Down syndrome screening is relatively high.

Is non-invasive DNA better or amniocentesis better?

Non-invasive technology cannot replace amniocentesis, so there is no question of which is better, non-invasive or amniocentesis. The medical community believes that both non-invasive and Down syndrome screening fall within the scope of screening, while biopsy is for diagnosis.

The common procedure now is that pregnant women first undergo Down syndrome screening. If the Down syndrome screening shows high risk, amniocentesis is performed to obtain fetal DNA for confirmation. The advantage is that the results are highly accurate. The disadvantage is that amniocentesis is invasive and there is a risk of infection and miscarriage. There are different opinions on the specific probability. If the hospital and the doctor are of good level, the risk is around 0.5%, but I have also seen risk reports of around 2%.

The non-invasive test actually involves drawing blood after a high-risk Down syndrome screening to test the free DNA of the fetus in the blood to check whether there are defects in chromosomes 13, 18, and 21. Some people say that the accuracy is high only for three chromosomes, and the accuracy for other chromosomes is limited. In fact, if other chromosomes have defects, various miscarriages may easily occur, and the fetus may be difficult to save. However, if chromosomes 13, 18, and 21 have defects, the accuracy is very strong and the fetus will not miscarry. If the non-invasive DNA test shows a high risk again, then amniocentesis will be necessary to confirm the diagnosis. Therefore, although it seems that one more test is done, it actually avoids risks and unfavorable factors. Moreover, all non-invasive projects provided by third-party institutions now come with insurance. Generally speaking, if the non-invasive test is also high-risk and a puncture is required for diagnosis, the cost of amniocentesis will be reimbursed.

The "Technical Specifications for Prenatal Screening and Diagnosis of Fetal Free DNA in Peripheral Blood of Pregnant Women" issued by the state mentioned that people who should use non-invasive tests with caution include:

(A) High-risk antenatal screening during early and mid-pregnancy.

(2) The expected age at the date of delivery is ≥ 35 years old.

(iii) Severe obesity (BMI>40).

(iv) Conception through in vitro fertilization-embryo transfer.

(5) There is a history of giving birth to a fetus with chromosomal abnormalities, excluding cases where the couple has chromosomal abnormalities.

(6) Twin or multiple pregnancy.

(VII) Other circumstances that the physician believes may affect the accuracy of the results.

When pregnant women with the above conditions are tested, the accuracy of the test decreases to a certain extent and the detection effect is still unclear.

For Down syndrome screening for older pregnant women, please consult an experienced obstetrician.

The following are the limitations of the two detection methods.

The current non-invasive DNA test targets chromosomes 13, 18, and 21. It is not responsible for the results of other chromosomes and has certain limitations in its detection range. So it doesn’t mean that there are no problems with non-invasive testing and the child will definitely be fine. There is still a risk of other chromosomal diseases.

Amniocentesis is still the "gold standard" and the means of final diagnosis. The amniotic fluid can be used for comprehensive chromosome analysis and gene chip testing. The detection range is wider than that of non-invasive DNA, but pregnant women have to bear certain risks (about 0.5%, no unified conclusion).

Overall, Down syndrome screening is a low-cost test. Amniocentesis has the highest accuracy rate and the widest detection range (amniotic fluid samples can be used for many tests, including more comprehensive chromosome analysis).