This is also one of the biggest sticking points during pregnancy, and we often encounter mothers-to-be and their husbands in the clinic who can’t make up their minds after a long discussion about this. The more choices there are, the more tangles there are. In addition to serological indicators, ultrasound soft indicators can also be added to the screening program. In addition to serological indicators, ultrasound soft indicators can be added. Now there is an additional screening NIPT (Noninvasive Fetal DNA Test) and of course the direct option of amniocentesis. Each method has its own corresponding indications, contraindications, advantages and disadvantages, and no method is perfect, which is why there are tangles and barriers to choice. In order to reduce the barriers to choice, the following is a comparison of “Down screening”, “non-invasive” and “amniocentesis” for reference only. If you are still hesitant after reading this article, you are basically close to the “choice barrier”. How to deal with the “choice barrier”? Please click “Read the original article” to see my previous article “Pregnancy and Childbirth: The Choice Barrier”. Down’s syndrome screening is the process of taking the mother’s peripheral blood in early to mid pregnancy, measuring the appropriate biochemical markers, combining the week of gestation, maternal age, weight and other information, and using professional screening software to calculate the risk of chromosomal abnormalities in the fetus. There are serumonly screening programs and combined serum screening programs with ultrasound soft markers. For example, the “Early Down” test involves taking the mother’s peripheral blood in early pregnancy to measure the appropriate markers and then measuring the fetal NT (nuchal translucency) to calculate the risk of the fetus having a chromosomal abnormality. 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 that you undergo an amniocentesis. However, please note that low risk does not mean “no risk”, it means that the risk of chromosomal abnormality is less than that of the general population, but the fetus is still at some risk of chromosomal abnormality, but the risk is less. (1) Only the peripheral blood of the pregnant woman needs to be taken, no puncture is needed and there is no trauma to the fetus and the pregnant woman; (2) The price is low, usually 150-300 RMB; (3) Certain serological indicators of the pregnant woman can predict the risk of not only trisomy 21, trisomy 18, trisomy 13 and neural tube defects, but also sex chromosome abnormalities and structural abnormalities, as well as certain pregnancy complications (such as preeclampsia). There is also some value in the early prediction of sex chromosome abnormalities and structural abnormalities, as well as certain pregnancy complications (e.g., pre-eclampsia). Limitations: (1) Strict requirements for gestational age: 11-13 weeks and 6 days for early and 14-20 weeks for mid-tons; (2) Risk calculation only for trisomy 21, trisomy 18, trisomy 13 and neural tube defects, no specific risk values can be given for other chromosomal number and structural abnormalities; (3) Expected detection rate of chromosomal abnormalities is 60-90%, with a false positive rate of 3.5 %. (3) The expected detection rate of chromosomal abnormalities is 60%-90%, and the false positive rate is 3.5%-8% (depending on the screening strategy); (4) Screening is not the same as confirming the diagnosis, if the screening result indicates high risk, further prenatal diagnosis is needed, if it indicates low risk, it does not mean that the fetus is completely normal; Indications for early screening: Early screening can be done for all singleton and twin pregnancies. However, for pregnant women with multiple pregnancies (three pregnancies or more) or multiple pregnancies with one fetal death in utero, NT is feasible at this time, but serologic screening is not done. Early NT is also encouraged in advanced maternal age because 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., heart malformations, septal hernia, etc.), genetic syndromes, etc. in the fetus. However, it is important to inform that screening is not a diagnosis and prenatal diagnosis should be considered for women of advanced maternal age, even if they are at low risk for early onset of NT. Indications for mid-tang: Pregnant women with a singleton pregnancy who are younger than 35 years old (referring to the age of the pregnant woman at the time of the expected delivery). Non-invasive fetal chromosome aneuploidy testing (NIPT) NIPT is performed by collecting peripheral blood from pregnant women, extracting free DNA from the fetus, and using next-generation high-throughput sequencing combined with bioinformatics analysis to determine the risk of fetal chromosome aneuploidy. Advantages: (1) Only the peripheral blood of the pregnant woman needs to be extracted, no puncture is required, and there is no trauma to the fetus and the pregnant woman; (2) The detection range is large: 12-24 weeks of gestation. (3) The expected detection rate is much higher than that of Down’s syndrome screening: the detection rates of trisomy 21, trisomy 18 and trisomy 13 are higher than 99%, and the false-positive rate is less than 1%, generally about 0.05%, which is an “advanced screening”. Limitations: (1) Only for trisomy 21, trisomy 18 and trisomy 13 chromosomal disorders; (2) Can not diagnose other chromosomal abnormalities in number and chromosomal chimerism, translocation and other structural abnormalities; (3) The price is generally 2,000-3,000 yuan, which is 10 times higher than Down’s syndrome screening, and is relatively expensive as a screening method. (4) Although the detection rate is high, it is still a technical means of prenatal screening and cannot be used as a final prenatal diagnosis. Indications: Prenatal screening (including serum screening, or ultrasound genetic marker screening) for pregnant women at critical high risk (e.g., risk rate of 1/270-1/1000); those with contraindications to interventional prenatal diagnosis (pre-eclampsia, fever, bleeding tendency, untreated infection, etc.); pregnant women with precious children who refuse interventional prenatal diagnosis after being informed; pregnant women with extreme anxiety about interventional prenatal diagnosis; pregnant women who are unable to make an appointment for prenatal diagnosis; pregnant women with 35 years of age. Pregnant women who are unable to get an appointment for prenatal diagnosis; pregnant women aged 35-40 years who refuse invasive prenatal diagnosis; healthy young pregnant women with high risk of Down’s syndrome screening between 1/270 and 1/50; twin pregnancies for non-invasive DNA preferably combined with early NT screening results. Non-invasive DNA testing is not recommended in the following cases: high risk of Down’s screening greater than 1/50; pregnant women with abnormal prenatal ultrasound detection, including early pregnancy with nuchal translucency greater than 3.5mm, early to mid pregnancy with any fetal gross structural abnormality detected by ultrasound, abnormal amniotic fluid volume, severe intrauterine growth restriction, etc., three or more pregnancies in which one of the couple has a definite chromosomal structural or numerical abnormality. Pregnant women with fetuses suspected of having microdeletion syndrome, other chromosomal abnormalities or genetic disorders; pregnant women who have received allogeneic blood transfusion, transplantation, stem cell therapy, immunotherapy. Invasive fetal chromosome testing Fetal cells are obtained by amniocentesis (amniocentesis) or chorionic villus aspiration or cord blood aspiration for cell culture and karyotype analysis, of which amniocentesis is still the most used. Advantages: (1) It can detect all chromosome number abnormalities and large segments of chromosome structure abnormalities; (2) It is currently the “gold standard” for prenatal diagnosis of fetal chromosomal disorders. Limitations: (1) In general, puncture is relatively safe, but there is still a risk of individual puncture failure, miscarriage, infection and amniotic fluid leakage. (3) Chromosomal testing cannot be completely ruled out for minor structural changes in chromosomes, monogenic genetic disorders, polygenic genetic disorders, environmental and drug-induced intrauterine developmental abnormalities, low percentage of chimerism and maternal contamination. Indications for amniocentesis: maternal age ≥ 35 years; high risk of fetal chromosomal abnormalities as suggested by prenatal screening; previous history of adverse pregnancy and childbirth with fetal chromosomal abnormalities; pregnant women suspected of having chromosomal disorders in the fetus during prenatal screening; one of the spouses is a carrier of chromosomal abnormalities; pregnant women may be carriers of certain X-linked genetic disorders; history of adverse pregnancy and childbirth or exposure to specific teratogenic factors. ICSI (intracytoplasmic single sperm injection) has been advocated in recent years as an indication for amniocentesis. Conclusion: Early screening has a higher detection rate than intermediate screening; non-invasive screening has a higher detection rate than screening; amniocentesis has the highest detection rate; screening for low risk does not mean no risk; screening for high risk amniocentesis results in a majority of normal results; screening for trisomy 21, trisomy 18 and trisomy 13, in addition to screening for some sex chromosome abnormalities and chromosome structural abnormalities, and neural tube defects; and A positive non-invasive screen still requires amniocentesis; ● Screening is risk-free, and amniocentesis has a relatively low, manageable, and acceptable risk.