Down’s syndrome screening is a test that calculates the risk factor for having a fetus with congenital defects by drawing serum from a pregnant woman and measuring the concentrations of alpha fetoprotein, chorionic gonadotropin and free estriol in the mother’s serum in combination with her expected date of delivery, her weight, her age, her weight, and her gestational week at the time of blood collection. What is Down’s test? It is an economical, simple and non-invasive test to detect high-risk pregnancies with certain birth defects from pregnant women so that a definitive diagnosis can be made and the birth rate of abnormal fetuses can be minimized. Prenatal screening, as it is currently known, usually refers to the detection of high-risk pregnancies with congenital defects through the use of maternal serum markers. The optimal time for screening is between the 9th and 14th weeks of pregnancy, called early pregnancy screening. Missing this time requires mid-pregnancy screening, which also calculates the risk but is more damaging to the mother if the final diagnosis is positive. Regardless of the early or mid-pregnancy period, the results are usually available within a week after the blood is drawn, and there is no need to be alarmed if the results are high-risk, as further chorionic villus biopsy (early stage), amniocentesis and fetal chromosome testing (mid-stage) are required to make a definitive diagnosis. Why is screening for Down syndrome necessary? Children with Down’s syndrome have severe intellectual disability, congenital stupidity, tongue-stretching dementia, inability to take care of themselves, and complex cardiovascular disease, requiring long-term care from family members, which can cause great mental and financial burden to the family. Down syndrome is an episodic disease, so every pregnant woman can give birth to a Down’s child. The chance of having a Down’s syndrome baby increases with the age of the mother. How do I get screened? To screen for Down’s syndrome, no fasting is required. Maternal serum is drawn and tested for pregnancy-associated plasma protein A (PAPP-A), free hCGB subunits (two early tests), or alpha-fetoprotein (AFP), and chorionic gonadotropin (HCG), and free oestradiol (uE3) (three intermediate tests), which, in conjunction with the expected date of delivery, body weight, age, and gestational age at the time of the blood sample collection, will be used to calculate the number of “Down’s babies. “The risk factor for Down’s syndrome is calculated by combining the expected date of delivery, weight, age and week of pregnancy at the time of blood collection, and 80% of Down’s syndrome babies can be detected. Precautions During prenatal screening, pregnant women are required to provide detailed personal information, including year of birth, last menstrual period, weight, insulin-dependent diabetes mellitus, twin births, whether they are smokers or not, and history of abnormal pregnancies, etc. Since the risk rate statistics of the screening test need to be corrected according to the above factors, it is very important to fill in the test form before the blood is drawn. What is Down syndrome? Down syndrome, also known as trisomy 21, means that the patient’s 21st pair of chromosomes is one more than normal (normal is one pair). Down syndrome screening is a risk value calculated from the serum levels of AFP, HCG, and uE3 of a pregnant woman, combined with the woman’s age, weight, and week of gestation. The cut-off value is 1/275 (this value may vary due to methodological differences). A value greater than this is considered high risk, while a value less than this is considered low risk. The probability of having Down’s syndrome (DS) in the general population (under 35 years of age) is 1/750. Down’s screening test, short for prenatal screening test for Down’s syndrome. The purpose is to determine the risk of the fetus having Down syndrome by testing the pregnant woman’s blood. If the results of the Down screening test show that the fetus is at a higher risk of having Down syndrome, further confirmatory tests – amniocentesis or chorionic villus testing – should be performed. How accurate is the Down screening test? According to the latest prenatal screening standards of the Ministry of Health, the detection rate of Down’s syndrome should be more than 70% by qualified testing organizations. It should be clear that the Down’s syndrome test can only help to determine the chances of the fetus having Down’s syndrome, but it cannot determine whether the fetus has Down’s syndrome or not. That is to say, when the blood test index is high, the chances of having a baby with Down’s syndrome are higher, but it doesn’t mean that the fetus must have problems. For example, pregnant women over 35 years old have a higher chance of having a Down’s syndrome baby, but it does not necessarily mean that their babies are sick. On the other hand, even if the test results are normal, there is no guarantee that the fetus will be free of the disease. Pregnant women with abnormal Down’s syndrome test results should undergo an amniocentesis or chorionic villus test. Only if the results of the amniocentesis or chorionic villus test are normal can Down’s syndrome be ruled out 100 percent of the time. What other diseases can be tested for with Down syndrome screening? Serum AFP, HGG, and uE3 tests can also screen for high risk pregnancies for Neural Tube Defects (NTD), Trisomy 18, and Trisomy 13. How will I know the results of the screening test? Pregnant women will be informed of the results by the clinic doctor when they return to the clinic for their routine antenatal checkup 1 week after the blood test. If the serum test is positive, a chorionic villus biopsy or amniocentesis will be needed to confirm the diagnosis. Treatment of high-risk pregnant women For high-risk pregnant women with trisomy 21 and trisomy 18 in the screening test, doctors should recommend amniotic fluid fetal karyotyping to rule out chromosomal chromosomes after checking the week of gestation and other factors, and for high-risk pregnant women with NTD, ultrasound should be used to rule out neurological developmental abnormalities, and the development of the fetus should be closely observed. It can also be recommended that pregnant women undergo amniocentesis for acetylcholine lipase examination to exclude the possibility of closed neural tube malformation and hidden spina bifida. Teach you to read and understand the Down’s syndrome screening report card (1) AFP (alpha-fetoprotein) AFP is a kind of specific globulin of the fetus, with a molecular weight of 64,000-70,000 daltons, and it may have the immune-regulating function of glycoprotein during pregnancy, which can prevent the fetus from being rejected by the mother. AFP is synthesized by the yolk sac in the early 1-2 months of gestation, and then mainly by the fetal liver, and a small amount of AFP can also be synthesized by the fetal digestive tract and enter the fetal circulation. Fetal blood AFP value rises rapidly at 6 weeks of gestation, reaches the peak at 13 weeks of gestation, and then gradually decreases with the progression of pregnancy to full term. AFP in amniotic fluid mainly comes from fetal urine, and its trend is similar to that of fetal blood AFP, and maternal blood AFP is derived from both amniotic fluid and fetal blood, but the trend is not the same as that of amniotic fluid and fetal blood. In early pregnancy, maternal blood AFP concentration was the lowest, gradually increased with the progression of pregnancy, peaked at 28-32 weeks of gestation, and then declined. The serum AFP level of pregnant women with congenital stupid fetus is 70% of normal pregnant women, i.e. the average MoM value is 0.7-0.8 MoM. Insulin-dependent diabetes mellitus, AFP is 10% lower. In pregnant women with high body weight, AFP is low; in smokers, AFP is 3% higher; in patients with abnormal liver function, AFP is higher. (2) Free hCGβ (free-beta-subunit-chorionic gonadotropin) The serum level of Free hCGβ is strongly elevated in pregnant women with congenital trisomy 21 fetuses, with an average MoM value of 2.3-2.4 MoM. In fact, there is no need for us to be too nervous when the MOM value of free-hcg is high. About: hCG is human chorionic gonadotropin synthesized by placental cells and consists of two subunits, a- and b-. HCG exists in two forms, the intact hCG and the separate b-chain. Both types of hCG are active, but only the hCG present in the b-single-chain form is the specific molecule for the assay. hCG enters the maternal blood just after fertilization and proliferates rapidly until the eighth week of gestation, then slowly decreases in concentration until the eighteenth to twentieth week of gestation and then remains stable. Both maternal serum HCG and β-HCG in congenital trisomy 21 fetuses are on a continuous upward trend, generally 1.8-2.3 MOM values and 2.2-2.5 MOM 18 trisomy 18 in usually pregnant women, and β-HCG exhibits reduced abnormality, generally ≤0.25 MOM as an important manifestation of a high risk of 18 trisomy 18. The MOM value is a ratio, i.e., the value of markers detected in pregnant women divided by the median value of normal pregnant women of the same gestational week, which is the MOM.Since the level of prenatal screening substances will vary greatly with the increase of gestational weeks, their values must be converted to multiples of the median (MOM) to “standardize” and facilitate clinical For example For example, a random pregnant woman with a gestational week of 14 weeks + 0 days free-HCG value: 28,800 mIU / ml gestational week of 14 weeks + 0 days of the median: 14,400 mIU / ml the MOM of this pregnant woman: 28,800/14,400 = 2, so if this indicator fluctuates, don’t pay too much attention to it, it may be due to the inaccurate calculation of the duration of the pregnancy, it is really not necessary to put yourself in a panic. There is no need to put yourself in a panic. (3) uE3 (free estriol) uE3 is the main estrogen produced by the placenta unit of the fetus. Due to the poor development of the adrenal cortex of the fetus, the synthesis of dehydroepiandrosterone sulfate, the precursor of uE3, is reduced, resulting in a decrease in uE3. Mothers carrying a fetus with congenital stupidity show reduced uE3 in their blood, with an average MOM value of 0.7. (4) Questions about trisomy 21, 18, and 13 Normally, there are 46 human beings with 23 pairs of chromosomes, and trisomy 21, 18, and 13 are the 21st, 18th, and 13th pairs of chromosomes of a fetus that are more than the normal 2, and 1 more than the normal 2, which is called trisomy XX. One of these trisomies, trisomy 21, is Down syndrome. Pregnant women of any age may conceive a fetus with chromosomal abnormalities, but the incidence of chromosomal abnormalities increases significantly with the age of the pregnant woman, for example, the incidence of chromosomal abnormalities in pregnant women under the age of 25 years is 1:1185, while at the age of 35 years, it is as high as 1:335, so pregnant women above the age of 35 years old need to do chromosomal testing. 1, Down’s syndrome screening for the possibility of checking: high-risk group is just to say that the fetus is more likely to be Down’s syndrome, low-risk group may also be Down’s syndrome 2, in all pregnant women about 1/10 of pregnant women screening is a high-risk group, high-risk group of 1 ~ 2/100 is Down’s syndrome, that is, there are pregnant women in the 1 ~ 2/1,000 is the Down’s syndrome 3, when the value of the blood test screening is greater than 1/270 for the high-risk group, normal value The normal value is about 1/700. The international standard is 1/270. 4. The Down’s syndrome screening value is a corrected value. Factors affecting the Down’s syndrome screening value are: maternal age, weight, gestational week, fetal secretion of fetal methyl protein, placental secretion of human chorionic hormone, drug factors, genetic factors. The human chorionic villus hormone may be affected if the human chorionic villus hormone exceeds the normal value due to the use of “Dolichol” during fetal preservation. (5) Diagnostic methods to determine whether the fetus is a Down’s syndrome child now the only medical means to do amniocentesis, fetal cell karyotyping, and enzyme testing, so as to make a diagnosis of fetal chromosomal disorders and metabolic genetic diseases. Amniocentesis: The amniotic fluid is extracted, and the cells of the fetus shed in the amniotic fluid are cultured to test the chromosomes of the cells (test for fetal chromosome 21). Extraction of amniotic fluid: 20 ml of amniotic fluid is taken. Risks are possible infection, leakage of amniotic fluid, miscarriage, likelihood of miscarriage (probability 0.1%) Culturing of fetal cells shed in the amniotic fluid, success rate 98%. Testing the cells for chromosomes (testing the fetus for chromosome 21) with 100% accuracy. Whether Down’s screening can detect the sex of the fetus Down’s syndrome is a common chromosomal disorder in human beings. Due to the fact that children with Down’s syndrome are severely mentally retarded and are unable to take care of themselves, Down’s screening is now performed on pregnant women in almost all developed countries. Down’s syndrome screening is a test for the risk of Down’s syndrome and has nothing to do with the sex of the fetus. free beta HCG is a test of the serum of the pregnant woman, not of the fetus. Importance Down’s syndrome screening refers to a screening test that is performed on a specific group of people (e.g., all pregnant women) without any indication of the corresponding disease, to screen out those at high risk of developing a particular disease for subsequent diagnostic tests. It should be clear that the purpose of screening is not to diagnose a disease, but to identify people who are more likely to have a particular disease. The screening and diagnosis of Down syndrome, trisomy 18, and congenital neural tube malformations is a systematic approach in which all pregnant women are screened to identify those whose fetuses are at higher risk of congenital stupidity, proboscis dementia, and other conditions for subsequent diagnostic testing, and if the fetus is ultimately diagnosed with one of these congenital conditions. The pregnant woman can make her own decision about whether or not to continue the pregnancy. The same screening method is used for each of these conditions. The risk of your fetus having each of the three congenital conditions is calculated by taking your age, weight, and venous blood levels of AFP and beta-HCG, along with other information about you (e.g., whether or not you are a smoker or a heavy drinker, etc.). Depending on the risk, you will get a positive (high risk) or negative (low risk) result. The way to do this is to draw chorionic villus blood or amniotic fluid for cell culture and then do a karyotyping analysis, if there is a trisomy 21 pattern, then the fetus can be diagnosed with Down’s Syndrome.AFP is the Chinese name for Alpha Fetoprotein, if the AFP in the mother’s blood and fetal amniotic fluid is elevated, it confirms that the fetus has a neural tube abnormality, i.e., Spina Bifida, Spina Dorsiflexion, Anencephaly, Microcephaly, and Hydrocephalus. Why Down’s Screening Down’s serum screening is a very effective way to check for Down’s babies, and any pregnant woman can carry a fetus with Down’s syndrome. In the past, it was thought that those >35 years of age were at high risk, and that the chances increased with increasing maternal age. It is now believed that 80% of Down’s syndrome occurs in pregnant women <35 years of age. Down's syndrome screening narrows the scope of the amniotic fluid test and does not miss pregnant women who may be carrying Down's babies. It is recommended that every pregnant woman undergoes Down's syndrome screening as a precautionary measure. Checking serum afp and hgg can also screen for high-risk pregnant women with neural tube malformations, trisomy 18 and trisomy 13. Issues to be aware of during the test There is no need for fasting for Down's syndrome screening, and it is sufficient to draw peripheral blood from the pregnant woman, but Down's syndrome screening is related to menstrual cycle, weight, height, exact gestational week, and size of the fetus. Generally speaking, 15-20 weeks of pregnancy is the best time for Down's syndrome screening. Mothers-to-be should not forget to make an appointment with their pregnancy doctor for the test.