Text/Reporter Li Li Editor/Liu Zhao Proofreader/Xiao Yuan
New Media Editor/Chen Xuanzhi
This article is edited by China Digital Science and Technology Museum and Science and Technology Daily "Science and Technology Life".
Interview experts
Jiang Yulin
Deputy Director and Associate Professor of Obstetrics and Gynecology, Union Hospital
On September 3, 2022, a child was born in Wangcheng District Maternal and Child Health Hospital, Shashi City, Hunan Province. Unfortunately, his birth was accompanied by a series of defects and diseases such as 13 long arm defect syndrome, brain development and iris defect. This means that the little boy is likely to have mental retardation, slow growth, abnormal appearance and almost impermanent growth.
Combing the context and main points of this tragedy, we will find that both boys and mothers have done BGI's "non-invasive DNA testing" and told them that this testing is comprehensive and advanced, with an "accuracy rate of 99.99%". And after several rounds of doctors' judgment based on "non-invasive and low risk", the mother gave up the puncture examination again, which eventually led to tragedy.
In July 13, the article "Cancer in Huada" (click here) reported this, which pushed the Huada gene to the forefront. Many people began to take risks to make a more comprehensive and accurate sheep puncture, or did they risk missing the inspection and do it non-invasively? Is this seemingly non-invasive DNA test really "foolproof"? It hurts to think about it. Is it worthwhile for pregnant mothers to take the risk of doing a puncture with high risk, high rate and high infection rate? Let's listen to Jiang Yulin, an obstetrician and gynecologist at Union Medical College Hospital.
Science Plus: What is puncture?
Jiang Yulin (hereinafter referred to as "Jiang"): At present, puncture is one of the most commonly used prenatal diagnostic techniques in China, which is called amniocentesis, or simply sheep puncture. Puncture is under the guidance of B-ultrasound, using slender extraction to detect the cells shed by the intermediate fetus, so as to evaluate the intrauterine situation of the fetus and whether it has diseases.
Science Plus: What is non-invasive DNA prenatal testing?
Jiang: Its standard name should be "Detection of Fetal Free DNA". It can analyze the baby's condition by collecting the peripheral blood of pregnant women and extracting free DNA (mother's and baby's DNA) from the blood. This technique provides a second choice for pregnant mothers who don't want to have puncture.
▲ Schematic diagram of fetal free DNA detection
Science Plus: Which is better, puncture or non-invasive DNA?
Jiang: Simply put, puncture is a prenatal diagnosis technique, and "detecting fetal free DNA" is a prenatal screening technique.
Compared with puncture, the advantage of noninvasive DNA testing is safety. There is no "needle" in pregnant women's stomach, and there is no risk after puncture. However, the limitation of this test is that it is not comprehensive. You can only get high risk or low risk, and you can't diagnose whether there is something wrong with the fetus. If the test results show that it is a high-risk fetus, further puncture is needed to confirm whether there is any problem with the fetus.
Science plus: noninvasive DNA can only check three pairs of abnormalities?
Ginger: The objects of "detecting fetal free DNA" are three pairs with high distortion rate: 2 1, 18 and 13. The consequences of these three pairs of abnormal numbers correspond to Down's syndrome, Edward's syndrome and Pato's syndrome respectively, which are the three most common genetic defects in newborns. This test can find out these three "three-body" situations (based on the normal one-to-two ratio, there is one more distortion), which are 2 1- trisomy, 18- trisomy and 13- trisomy respectively.
Science Plus: Why didn't Hunan's problem 13 be found out?
Jiang: Take Hunan as an example, its genetic defect is not "trisomy", but "long arm loss". In other words, it is not "one more" (abnormal quantity), but "one less structure" (abnormal quality).
Science Plus: Is noninvasive DNA really foolproof?
Jiang: Free DNA testing is just screening, but it can't be diagnosed. If the result is positive, further diagnosis is needed by puncture and karyotype analysis. In addition to false positives, this test also has a small probability of missing detection.
▲ Karyotypes of ▲2 1- 0/-trisomy syndrome (left) and patients (right)
Science Plus: Are screening and diagnosis the same thing?
Jiang: Screening is a general screening for a wider range of people. If there is a high risk, a diagnosis will be made. The means of prenatal screening include free DNA screening and serum screening, that is, Down's screening. Down's screening is not as accurate as noninvasive DNA. However, Down's screening is cheap, and the public can afford it without spending thousands of dollars.
Non-invasive risk is low, but few targets can be detected. The so-called accuracy rate of free DNA screening is 99.99%, which is only aimed at the "three-body" state of those three pairs. Puncture is a comprehensive diagnosis of 23 pairs, which can judge both quantity abnormality and quality abnormality. As a prenatal diagnosis, all the quantitative and morphological abnormalities can be detected with a detection rate close to 100%.
Science Plus: Who is Suitable for Noninvasive DNA?
Jiang: In 2022, the Health Planning Commission issued the "Technical Specification for Prenatal Screening and Diagnosis of Fetal Free DNA from Peripheral Blood of Pregnant Women" (referred to as "Technical Specification"). The technical specifications mainly include the basic requirements, scope of application, clinical service process, detection technology process and quality control indicators of prenatal screening and diagnosis of fetal free DNA in maternal peripheral blood. For example, it is stipulated that the institutions that carry out prenatal screening and diagnosis of fetal free DNA in peripheral blood of pregnant women should be qualified prenatal screening or prenatal diagnosis institutions. Institutions that carry out laboratory detection of fetal free DNA in peripheral blood of pregnant women should have the qualification of clinical gene amplification laboratory.
In addition, it also clearly points out the applicable population, cautious population and inapplicable population. The applicable population mainly includes: first, pregnant women whose serological screening shows that the risk value of common fetal aneuploidy is between the high-risk cut-off value and11000; Second, there are contraindications for prenatal diagnosis (such as aura, tendency, active period of chronic plasma infection, Rh blood group of pregnant women, etc.). ); 3. Those who are pregnant for more than 20+6 weeks and miss serological screening for a good time, but need to assess the risk of 2 1- trisomy syndrome, 18- trisomy syndrome and 13- trisomy syndrome.
Science Plus: Who Needs Puncture?
Jiang: Clinically, in China, all pregnant women over the age of 35 should be diagnosed. If you are under the age of 35, but scan, Down's screening and other abnormalities are found, and one of the husband and wife is sick or has given birth to a sick child, it is recommended to make a direct puncture diagnosis.
Science plus: What problems should be paid attention to in puncture?
Ginger: The most important point of puncture is to eliminate infection. Because a large part of the reason is that children have problems, and part of the reason is that pregnant women have other possible infections, such as colds, fever, wounds and so on. When doing puncture, bacteria will easily reach the puncture site, causing nosocomial infection, which is likely to happen.
Therefore, the puncture should be carried out when the pregnant woman is in good health. In addition, routine blood tests are needed, which can only be done if the white blood cells are not high and there is no inflammation.
For pregnant women who have the possibility of transmission at any time, such as hepatitis B carriers and HIV carriers, it is necessary to block them before operation and inject immunoglobulin to block their vertical transmission to the fetus. For some pregnant women with panda blood (Rh blood), in view of the problem that puncture may cause fetal edema and anemia, anti-D immunohistochemical histone should be injected before puncture.
Science Plus: When will the puncture be done?
Ginger: Puncture is better at 17-23 weeks of pregnancy, and the amount taken out is generally about 20-25ml. Puncture is risky and not recommended for every pregnant woman. Under normal circumstances, pregnant women under the age of 35 do not need to do sheep puncture if there is no abnormality in serum screening. The stab wound is so small that you don't need to be hospitalized. It usually takes a week to fully recover.
Science Plus: How do you assess the risk of puncture?
Jiang: Generally speaking, the probability of puncture risk is between one thousandth and two thousandths. But it is generally safe, and as a prenatal diagnosis, the benefits are obvious. Because doctors can make a definite diagnosis only when they get the results of fetal analysis, unlike screening results, they can only make indirect speculation and judgment.
Science plus: What is the accuracy of puncture?
Ginger: Actually, puncture is the process of obtaining specimens, that is, obtaining them. As for the follow-up examination, it is divided into traditional karyotype analysis, that is, the number and shape of large structural abnormalities. At present, the accuracy is close to 100%. But we can't check for tiny deletions or repetitions, and we can't determine the abnormalities of various genetic diseases. Such as deafness and autism.
At present, in clinic, for some pregnant women with special circumstances, such as having a child with genetic disease, there is a certain possibility of slight deletion, so we suggest making some more advanced or advanced molecules to diagnose. For example, we need to make a chip if we want to check tiny omissions and repetitions. If Chucky is sick, he needs to do gene sequencing.
Science Plus: How painful is it to wear a sheep?
Ginger: The pain mainly depends on the puncture site. Abdominal wall is not a particularly painful place, and the needle used for puncture is thinner than that used for blood drawing and injection. Many pregnant women have the same degree of pain as ordinary injections.
At present, it is generally not given to pregnant women, because the medicine used also depends on injection, which is more painful than sheep puncture.
Science Plus: Can Sheep Pierce the Fetus?
Ginger: The whole process of puncture operation is carried out under the guidance of ultrasonic monitoring, avoiding the fetus, determining the position and situation of the fetus, and then performing puncture extraction, so it will not hurt the fetus.
Science Plus: Besides puncture, what other prenatal diagnoses can be used to check the baby?
Ginger: There are the following kinds: one is villus biopsy, which is done once every three months, so you can check the baby's condition.
The second is cord blood puncture. If you miss the initial prenatal diagnosis, you can do cord blood puncture.
The third is non-invasive DNA screening, which is a relatively advanced examination at present. By checking the content of the baby's DNA in the mother's blood, the baby's condition can be indirectly reflected. The detection accuracy of three body 2 1-, trisomy 18- and trisomy 13- can reach about 99%.
Finally, Down's screening, some pregnant mothers may only be willing to do ordinary serological Down's screening, and the detection rate, gender and specificity of Down's screening for baby problems are slightly poor.
Science Plus: How to treat birth defects in cases?
Jiang: Actually, people don't realize the risk of getting sick. At the same time, I am too afraid of the puncture rate. I hope you don't look at this technique with too much prejudice, don't deny it with subjective feelings, but learn more about puncture knowledge.
In fact, clinically, doctors should do a good job before and after the examination. For example, before puncture, patients should be informed of what preparations need to be made and the risks of seeing a doctor. After the inspection, we should consider the low probability of missed detection and make a scientific comprehensive judgment instead of simply preaching in sequence. Only after inspection, good technology will produce good inspection service.
At present, more attention is paid to the pre-examination in clinic, and the examination results of a technology are too arbitrary and simple, which will lead to a bad place for a new technology. In fact, the detection of fetal free DNA needs the approval of more pregnant women and more clinicians, and the corresponding training and education work should be done well.
▲ Lu Yuming, a professor at Chinese University, discovered fetal DNA in pregnant women's plasma at 1997, and then explained the basic parameters of this phenomenon and developed a series of innovative analytical techniques, thus creating a non-invasive prenatal diagnosis (photo: official of Chinese University).
Science Plus: Is prenatal diagnosis the same at home and abroad?
Jiang: At present, the process and thinking of prenatal diagnosis at home and abroad are basically the same, and there is not much difference. Basically, it is recommended to select high-risk groups for puncture, and other pregnant women can do some screening first. Generally speaking, domestic and foreign countries are at the same level in disease prevention and treatment.
However, the degree of domestic technology popularization may be worse than that of foreign countries. For example, in a regular hospital puncture, "detecting fetal free DNA" is relatively standard, but in a primary hospital or a remote area, due to the limitations of equipment, personnel and environmental conditions, there will be a big deviation.
In addition, China's technology may not be as mature as that of foreign countries. For example, in addition to some regular hospitals in China, some institutions or commercial laboratories are also doing prenatal diagnosis and screening. However, it is still unknown how much quality they have done has been assessed and evaluated by the health administrative department.
Science Plus: What is the greater challenge of clinical prenatal screening and diagnosis?
Jiang: The bigger challenge is that the overall size of pregnant women in China continues to grow, the proportion of elderly pregnant women continues to increase, and the demand for pregnant healthy babies is increasing, which is in deep contradiction with the lack of prenatal screening and diagnosis services and the improvement of work quality at this stage.
Science Plus: What do you think of the hot non-invasive DNA testing?
Jiang: In this case, prenatal detection of fetal free DNA, as a new high-performance prenatal screening technology, can effectively supplement the existing prenatal screening and diagnosis technology system if it can be carried out reasonably and scientifically in clinic. But at the same time, how to implement effective and scientific management and technology for this new technology with some characteristics of high-tech industry is a severe challenge for health administrative departments and industry experts.
Produced by: Popular Science Kitchen
Producer: Science News | Science Plus Client
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The above is about whether August sheep is really so terrible, and it is about sharing intrauterine diagnosis. I saw the fate of the sheep girl in August, I hope this can help everyone!