1.Which is more accurate, Early Tang or Mid Tang? As a screening tool, neither the CT scanner nor the CT scanner can confirm the diagnosis, so it is not accurate, and there is no such thing as “accuracy rate”. The “detection rate” and the “false positive rate” are usually used to evaluate a certain screening tool. A high detection rate and a low false-positive rate are the criteria for a good screening tool. From the current situation in China, the detection rate of pretang is higher than that of mid-tang, and the false-positive rate is lower than that of mid-tang. The detection rate of Zao Tang is about 80% and the false positive rate is about 5-7%, while the detection rate of Zhongtang is about 55% and the false positive rate is about 5-8%. 2.Why don’t a lot of places do it if the NT is more accurate? Early Tang must be added to do NT, NT test on the ultrasound doctor’s technical requirements and ultrasound machine configuration requirements are very high, the domestic really get the British Fetal Medicine Foundation NT certified doctors are not many. The examination also depends on the baby’s position, if the baby’s position is not good, can not get the best detection plane, NT measurement will not be accurate, generally a NT measurement takes at least 10 minutes or so, so the NT test is a painstaking thing. 3.Do I still need to do the Mid-Tang after doing the Early Tang? Both Early and Mid-Tang are mainly for screening the risk of Down syndrome, and the practice varies according to the different screening strategies. If a single screening is performed, you do not need to do an interim test after doing an early test; if a combined screening strategy is adopted, you need to do an interim test after doing an early test, and then calculate the combined risk. Suggestion: We advocate not to use the outdated methods of Early Down and Middle Down. 4. The result of Down’s syndrome screening is high risk. Since the false positives are not low, is it okay if I want to be retested again? The principle of Down’s syndrome screening is not to repeat the test, because screening is not a diagnosis, but a general judgment of the risk level, and different testing systems may differ in their judgment of the same sample. Repeated testing can also bring about confusion in interpretation. If the results of two tests are different, which one should you actually believe? Suggestion: Don’t use the outdated methods of Early Tang and Middle Tang. 5. Why do I need to do it if the detection rate of the CT scan is not high, only about 55%? Although the detection rate of CFS is not satisfactory, the detection rate of Down syndrome is only 30% if we do not do CFS and only use pregnant women over 35 years old as a screening tool. Although the detection rate of Down’s syndrome screening is not as high as we expect, but it is still much better than not doing screening. 6. Is it impossible to do Down’s syndrome screening for twin fetuses? It is not recommended to assess the risk of Down’s syndrome in twin fetuses by maternal serologic indicators (e.g., Mid-Tang) alone, but early Down’s syndrome screening during early pregnancy combined with ultrasound markers (including NT, tricuspid regurgitation, etc.) of each fetus plus maternal serologic indicators is valuable, and the detection rate of twin fetuses with NT plus serologic screening is 75-80%, with a false-positive rate of about 5%. Gospel: Prenatal noninvasive DNA testing is currently available to detect pregnant women carrying twins. However, it is only carried out in the prenatal diagnostic departments of designated hospitals, and it is necessary to determine whether it is suitable for testing by non-invasive genetic testing after specialized prenatal counseling for twins. 7.What should I do if I have a low risk of Down screening and have ultrasound soft indicators such as strong light spots in the ventricles? Non-invasive DNA testing. 8.Down’s screening suggests critical risk what to do? Non-invasive DNA testing. 9.Do I need to do amniocentesis if I don’t pass the sugar screening? Sugar screening” and “Down screening” are different, “sugar screening” is diabetes screening, “Down screening” is Down syndrome screening, the latter high-risk need to do amniocentesis, the former high-risk need to do amniocentesis. Amniocentesis, the former did not pass is gestational diabetes, there is no need to do the support wear. You can not laugh, clinical really met “sugar screening” did not pass the prospective mothers to ask to do amniocentesis, really fainted! 10, 35 years old can not do the Down syndrome, must do amniocentesis? The age of 35 years old belongs to the age of high-risk, older than 35 years old pregnant women are recommended to direct prenatal diagnosis (such as amniocentesis, etc.) to diagnose whether or not pregnant with a child with Down’s syndrome. However, it doesn’t mean that you can’t have Down’s syndrome screening at 35 years old. Pregnant women of advanced age can still have Down’s syndrome screening after fully recognizing the value of the test (i.e., Down’s syndrome screening is a risk assessment, and a low risk means that it is less likely that you will have a Down’s syndrome baby, but it does not mean that you are not at risk). After that, Down screening can still be done. I would recommend non-invasive DNA testing though. 11.We are a normal couple and there is no Down’s syndrome in our family, why do you want me to do Down’s screening? About 95% of people with Down’s syndrome have normal parents and no Down’s syndrome in their family. It occurs as a result of an error in cell division during the early stages of fertilization of the egg, or an error in the division of the germ cells (sperm or egg). In less than 5% of cases, Down syndrome is associated with structural abnormalities of the parents’ chromosomes (e.g., translocations). Therefore, theoretically, regardless of whether there is a family history of Down’s syndrome, all pregnant people should be screened for Down’s syndrome, because all normal pregnancies are likely to develop Down’s syndrome, and the risk of Down’s syndrome for normal pregnant women under the age of 35 years is 1/700-1/800. 12. Since Down’s syndrome screening is inaccurate, and the non-invasive fetal DNA test is more accurate, why don’t you just replace the Down’s syndrome screening with a non-invasive one? At present, non-invasive fetal DNA testing is only for aneuploidy of chromosomes 21, 13 and 18. The report of non-invasive prenatal genetic testing mentions chromosomes 21, 18 and 13, but in fact it detects numerical abnormalities of all chromosomes. Your clinician will notify you if any other chromosomes are found to be problematic. From a health economics point of view, non-invasive fetal DNA testing is currently more costly and too expensive. 13. What is the difference between non-invasive fetal DNA testing and amniocentesis? Non-invasive fetal DNA test is to determine whether there is a dosage change (e.g. addition or deletion) of the above chromosome segments through the measurement of the relative content of the target region of DNA (e.g. chromosome 21, 13, 18) from the fetus in the peripheral blood of the mother and does not allow you to see all the information of the fetal chromosomes. Fetal chromosome examination is able to detect chromosome number and structural abnormalities. Noninvasive fetal DNA testing is currently part of the Down’s Advanced Screening, which has a detection rate of about 99% for Down’s syndrome and a false positive rate of less than 1%. Amniocentesis is the gold standard for prenatal diagnosis.