1.Which is more accurate, Early Tang or Mid Tang? As a screening tool, neither the CT scan nor the CT scan 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 (including NT + maternal blood PAPP-A + β-hCG) 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 85%, the detection rate of Zhongtang is 65-75%, and the false positive rate is 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, need the best ultrasound equipment and the highest level of ultrasound doctor, 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 20 minutes or so, so the NT test is the main bottleneck of the early Tang can not be carried out on a large scale. 3.Do I still need to do the NT if I have done the NT? 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 you adopt the combined screening strategy, you need to do Down’s Syndrome test after the Early Down’s test, and then calculate the combined risk, the screening rate can be increased to 90%. 4.The result of Down’s syndrome screening is high risk, since the false positive is not low, can I 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 lead to confusion in interpretation. If there is no error in the calculation of gestational weeks, repeated Down’s syndrome screening is not recommended. 5. Since the detection rate of Down’s syndrome is not high, only about 65%, why do we need to do it? Although the detection rate of Down’s syndrome screening is not satisfactory, if you don’t do Down’s syndrome screening and only use the age of pregnant women over 35 as a screening tool, the detection rate of Down’s syndrome is only 30%, so something is better than nothing. 6. Is it true that twin fetuses can’t be screened for Down’s syndrome? It is not recommended to evaluate 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%. 7.What should be done if Down’s syndrome is low risk and there are soft ultrasound indicators such as ventricular bright spots? Ultrasound should first rule out the presence of combined fetal structural malformations and other genetic markers. If there are isolated ultrasound markers, the likelihood ratio (i.e., increased risk of Down syndrome) and background risk of different ultrasound soft markers should be used to re-correct the risk value of Down syndrome to decide whether invasive prenatal diagnosis is needed. 8. What if Down’s syndrome screening suggests a critical risk? Different screening methods will suggest different risk classifications. Some screening strategies only have low risk and high risk, and invasive prenatal diagnosis (e.g. amniocentesis) is recommended for high risk, while some screening strategies may suggest invasive prenatal diagnosis or non-invasive prenatal screening if there is a critical risk. 9.Do I need to do amniocentesis if I don’t pass the glucose screening? “Sugar screening and Down screening are different, “sugar screening” is diabetes screening, “Down screening” is Down syndrome screening, the latter high-risk screening. Down syndrome screening, the latter high-risk need to do amniocentesis, the former did not pass is gestational diabetes, there is no need to do the adoption of 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? 35 years of age belongs to the age of high-risk, China’s maternal and child health care law provides that pregnant women older than 35 years of age are recommended to direct prenatal diagnosis (such as amniocentesis) to confirm whether the child with Down syndrome. 11. Why do I need to undergo Down’s syndrome screening if my husband and wife are normal and there is no Down’s syndrome in their family? About 95% of people with Down’s syndrome have normal parents and no Down’s syndrome in their family. Down’s syndrome occurs when there is an error in cell division in the early stages of fertilization of the egg or in the division of the germ cells (sperm or egg). Only less than 5% of Down syndrome occurrences are associated with structural abnormalities of the parents’ chromosomes (e.g., translocations). Therefore, theoretically, regardless of whether there is a family history, 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 35 years of age is 1/700-1/800. 12. Since Down’s syndrome screening is inaccurate and non-invasive fetal DNA testing is more accurate, why not just replace Down’s syndrome with non-invasive? (1) The current non-invasive fetal DNA test is only for aneuploidy of chromosomes 21, 13 and 18, while Down’s syndrome screening also has a certain screening effect on the aneuploidy of other chromosomes and some chromosomal structural anomalies; (2) some serological indicators in Down’s syndrome screening are related to the occurrence of certain pregnancy complications, and they have an early prediction of the value of pregnancy complications (such as preeclampsia, etc.); (3) from a health Economically speaking, the cost of noninvasive fetal DNA testing is relatively high, and it is not yet suitable to be carried out as a first-line screening tool. 13. What is the difference between non-invasive fetal DNA testing and amniocentesis? Non-invasive fetal DNA test is through the maternal peripheral blood from the fetus of the DNA target region (such as chromosome 21, 13, 18) of the relative content of the measurement to determine whether there is the existence of the above chromosome segments of the dose changes (such as additions or deletions), and can not see all the information of the fetal chromosomes. Amniotic fluid cells contain cells shed from the fetus, and culturing these shed cells can visualize the fetal chromosomes and can detect abnormalities in chromosome number and structure. Non-invasive fetal DNA testing is currently part of the Down’s Advanced Screening, which has a detection rate of about 99% for Down’s syndrome, with a false positive rate of less than 1%. And amniocentesis is the gold standard for prenatal diagnosis. Non-invasive cannot replace amniocentesis. Amniocentesis is still recommended for high risk non-invasive results.