After pregnancy, every pregnant woman will encounter a knot is the screening and diagnosis of Down syndrome, which is also one of the biggest knot during pregnancy, often encountered in the clinic, some mothers-to-be and their husbands discuss this for a long time or still can not make up their minds. The more choices there are, the more complications there are. There are early pregnancy screening, mid-pregnancy screening, combined early and mid-pregnancy screening, duplex, triple or quadruplex screening, and there are also various combinations of Integrated, Continuous Combined, Contingent, and Sequential in the early and mid-pregnancy screening program, and in addition to the serologic indicators, ultrasound can also be added to the soft indicators. The screening program is now adding a new screening test for N. Nowadays, there is an additional screening test, NIPT (Non-Invasive Fetal DNA Test), and of course, amniocentesis can also be chosen directly. Each method has its own corresponding indications, contraindications, as well as advantages and disadvantages, no method is perfect, so there will be tangled, so there will be obstacles to choice. In order to minimize the obstacles to choice, the comparison of “Down screening”, “non-invasive” and “amniocentesis” is as follows, for reference only. If you are still hesitant after reading this article, you are basically not far from the “choice barrier”. How to deal with “choice disorder”? Please click “read original” to refer to my previous article “Pregnancy and Childbirth? of my previous article “Pregnancy and Childbirth The Choice Barrier”. Down’s syndrome screening The so-called Down’s syndrome screening is a procedure in which the mother’s peripheral blood is drawn during early and middle pregnancy to determine the appropriate biochemical markers, and the risk of chromosomal abnormalities in the fetus is calculated by professional screening software after combining the information of the week of gestation, the age of the pregnant woman, and her weight. In the Down’s syndrome screening program, there is a serum only program and a combined program of serum screening and ultrasound soft markers. For example, in the case of “Early Down”, the risk of chromosomal abnormalities is calculated by taking the mother’s peripheral blood during early pregnancy and measuring the NT (nuchal translucency) of the fetus. If the risk value exceeds a set cut-off value (e.g. 1/270), it is defined as high risk and your doctor will usually recommend amniocentesis. Low risk does not usually require amniocentesis, but please note that low risk does not mean “no risk”, it just means that the risk of chromosomal abnormalities in the fetus is less than that in the general population, but the fetus is still at some risk of chromosomal abnormality, but the risk is less. Advantages: (1) only need to extract peripheral blood of pregnant women, no need to puncture, no trauma to the fetus and pregnant women; (2) low price, generally 150-300 yuan; (3) some serological indicators of pregnant women can not only predict the risk of 21-trisomy, 18-trisomy, 13-trisomy and neural tube defects, but also for the abnormalities of chromosomes and structural anomalies, as well as some pregnancy complications (such as pre-eclampsia). e.g., preeclampsia) are also of value for early prediction. Limitations: (1) Strict requirements for gestational age: 6 days at 11-13 weeks for the Early Down, 14-20 weeks for the Middle Down; (2) Risks are calculated only for trisomy 21, trisomy 18, trisomy 13, and neural tube defects, but not for other chromosomal abnormalities or structural anomalies; (3) Expected chromosomal abnormality detection rate of 60%-90%, with a false positive rate of 3.5%; and (4) Risk of chromosomal anomalies of 3.5%. False-positive rate is 3.5%-8% (depending on the screening strategy); (4) Screening is not the same as diagnosis, if the screening result suggests high risk, further prenatal diagnosis is needed, if it suggests low risk, it doesn’t mean that the fetus is completely normal; Indications for the early detection: all single and twin pregnancies can be done early detection. However, for pregnant women with multiple fetuses (three or more pregnancies) or multiple fetuses with one fetus stillborn in the uterus, the NT test is feasible at this time, but serologic screening is not done. Early detection is also encouraged for women of advanced maternal age, as the significance of NT testing is not only to assess the risk of chromosomal abnormalities, but also to assess the risk of large structural malformations (e.g., cardiac malformations, septal hernias, etc.), genetic syndromes, etc., in the fetus. However, it is important to note that screening is not a diagnosis, and that prenatal diagnosis should be considered for women of advanced maternal age, even if the risk of early Down’s syndrome is low. Indications for mid-tang: Pregnant women with singleton pregnancies who are less than 35 years of age (the age of the mother at the time of the expected date of delivery). Non-invasive fetal chromosome aneuploidy testing (NIPT) NIPT is a procedure that collects peripheral blood from pregnant women, extracts free DNA from the fetus, and uses next-generation high-throughput sequencing combined with bioinformatics analysis to derive the risk rate of chromosome aneuploidy in the fetus. Advantages: (1) Only the peripheral blood of pregnant women needs to be extracted, no need for puncture, no trauma to the fetus and pregnant women; (2) The test can be performed in a wide range of gestational weeks: 12-24 weeks. (3) The expected detection rate is much higher than Down’s syndrome screening: the detection rate of trisomy 21, trisomy 18 and trisomy 13 are all higher than 99%, and the false-positive rate is lower than 1%, usually around 0.05%, which is “advanced screening”. Limitations: (1) only for the three chromosomal disorders of trisomy 21, trisomy 18 and trisomy 13; (2) the number of other chromosomal abnormalities and chromosomal chimeras, translocations and other structural abnormalities can not be diagnosed; (3) the price of 2,000-3,000 yuan, which is 10 times more than the Down’s syndrome screening, as one of the means of screening, the price is relatively expensive. (4) Although the detection rate is very high, it is still a technical means of prenatal screening and cannot be used as the final prenatal diagnosis. Indications: prenatal screening (including serum screening, or ultrasound screening of genetic markers) critical high-risk pregnant women (such as the risk rate of 1/270-1/1000); contraindications to interventional prenatal diagnosis (preeclampsia, fever, hemorrhagic tendencies, infections have not yet been cured, etc.); pregnant women with precious children, pregnant women who refused to participate in interventional prenatal diagnosis after being informed; pregnant women with extreme anxiety about interventional prenatal diagnosis; pregnant women who can not make an appointment to the prenatal diagnosis Pregnant women who are unable to make an appointment for prenatal diagnosis; Pregnant women aged 35-40 years who refuse invasive prenatal diagnosis; Healthy young pregnant women with a high risk of Down’s syndrome, between 1/270-1/50; Twin pregnancies for whom noninvasive DNA is preferable in combination with the results of NT screening in early pregnancy. Non-invasive DNA testing is not recommended in the following cases: high risk of Down’s syndrome greater than 1/50; pregnant women with abnormal prenatal ultrasound testing, including early pregnancy with nuchal translucency greater than 3.5 mm, early and mid-pregnancy ultrasound findings of any fetal macrostructural anomalies, abnormalities in amniotic fluid volume, and severe intrauterine growth restriction; pregnant women with three or more pregnancies in which one of the partners has a definite chromosomal structural or numerical abnormality; pregnant women with suspected microdeletions in both fetuses. Pregnant women whose fetus is suspected to have microdeletion syndrome, other chromosomal abnormalities or genetic disorders; Pregnant women who have received allogeneic blood transfusion, transplantation surgery, stem cell therapy, immunotherapy. Invasive fetal chromosome testing Fetal cells are obtained through amniocentesis (amniocentesis) or chorionic villus puncture or umbilical cord blood puncture for cell culture and chromosome karyotyping, with amniocentesis being the most widely used. Advantages: (1) It can detect all chromosome number abnormalities and large segments of chromosome structural abnormalities; (2) It is the “gold standard” for prenatal diagnosis of fetal chromosomal disorders. Limitations: (1) In general, amniocentesis is relatively safe, but there are still individual risks of failure of amniocentesis, causing miscarriage, infection, amniotic fluid leakage, and the overall fetal loss rate of amniocentesis is about 0.5%; (2) There are individual differences in cell culture, which does not ensure 100% success; (3) Chromosome testing is useful in the detection of chromosomal micro-structural changes, monogenetic disorders, polygenic disorders, and intrauterine fetal development caused by environment and drugs. (3) Chromosomal testing cannot completely exclude intrauterine developmental abnormalities caused by microchromosomal alterations, monogenic genetic diseases, polygenic genetic diseases, environmental and drug-induced intrauterine developmental abnormalities, low-proportional chimerism, and maternal pollution. Indications for amniocentesis: maternal age ≥35 years; prenatal screening suggests a high risk of fetal chromosomal abnormalities; previous adverse maternal history of fetal chromosomal abnormalities; prenatal examination of pregnant women suspected of fetal chromosomal disorders; one of the spouses is a carrier of chromosomal anomalies; pregnant women may be a carrier of a certain X-linked genetic disease gene; there is a history of adverse maternal history or a history of exposure to specific teratogens. In recent years, some people advocate that ICSI (intracytoplasmic sperm injection) is also included in the indication of amniocentesis.