What does trisomy 21 risk mean? What is trisomy 18 risk and neural tube defects? What do AFP and HCG each stand for? What does the MOM value mean? When you get the Down’s syndrome screening report, these questions will confuse the parents-to-be, and now we will teach you to read your Down’s syndrome screening report. The Down’s syndrome screening is divided into early (11-13+6) and mid-term (15-19+6) screening: 1, early pregnancy Down’s syndrome screening (NT + free beta-hCG + PAPP-A) detection rate of about 70%; this test is mainly in the 11-13+6 weeks of pregnancy, the mother applied “ultrasound” and “blood” screening. The screening test is performed by both “ultrasound” and “blood sampling”. Ultrasound is used to clearly measure the thickness of the nuchal translucency (NT) and blood tests to measure PAPP-A and β-HCG in the mother’s serum to estimate the risk of Down syndrome in the fetus. 2. Mid-trimester Down syndrome screening (AFP + free beta hCG + uE3 ) has a detection rate of about 60%; the pregnant mother will have her blood drawn at week 15-19+6, and the hospital will test the serum values of AFP, beta-HCG, free estriol, etc., together with the mother’s age, weeks of pregnancy and weight, to calculate the risk of Down syndrome (trisomy 21), trisomy 18, and The risk of neural tube malformation. Your age, weeks of gestation and other basic information are crucial to the calculation of your risk, so please be sure to tell your doctor the truth when he or she asks for personal information. The detection rate of combined screening in early and mid pregnancy can be increased to 80-90%. Interpretation of the results: 1. nuchal translucencythickness (NT) is the maximum thickness of the soft tissue between the skin and fascia layers at the back of the fetal neck and can be measured by ultrasound. Most babies with Down syndrome have a thickening of the nuchal translucencythickness, which is not an indication of fetal abnormality, but rather a sign of increased risk of fetal abnormality. About one-third of fetuses with increased NT thickness have chromosomal abnormalities, half of which are Down syndrome. We usually consider that when NT reaches 3-4mm, routine serological screening is no longer done, but an invasive diagnostic test is done. 2. High-risk group: When the risk value of screening result 21-trisomy is greater than 1/270, and the risk value of 18-trisomy is greater than 1/350 for high-risk group, the high-risk group needs further examination to confirm the diagnosis. Special reminder that screening for high-risk Down’s syndrome can only detect about 70% of children with Down’s syndrome, and about 30% of children with Down’s syndrome are not in the high-risk group. 3.Critical high risk: If your screening value is between 1/270 and 1/1000, you are at critical high risk. 4. Single high risk: If you look at your Down screening report, we have a reference range after the PAPP-A, AFP and β-HCG values, if your value is outside this range, you are single high risk. Usually, the serological screening results for trisomy 21 mothers show AFP, uE3 ↓ and β-HCG ↑, and for trisomy 18 AFP, uE3 and β-HCG ↓. Of course your single elevated or decreased value does not necessarily mean trisomy 18 or 21, other maternal or fetal causes may also lead to abnormal maternal serological screening results. 5. High risk of open neural tube malformation: Fetal neural tube and abdominal wall defects allow AFP to leak into the amniotic fluid, causing a significant increase in maternal serum AFP, and serological screening results show elevated AFP beyond the normal value range. Other conditions associated with elevated maternal serum AFP include underestimation of gestational age, multiple births, fetal death, fetal abdominal cleft, umbilical bulge, esophageal atresia, intestinal obstruction, hepatic necrosis, polycystic kidney, renal agenesis, placental abruption, low amniotic fluid, preeclampsia, fetal growth restriction, maternal hepatocellular carcinoma teratoma, etc.; decreased serum AFP concentration: obesity, diabetes mellitus, trisomy 21 or 18, gestational trophoblastic disease , stillbirth. According to the latest reports, about 20% of children with Down’s syndrome are found in the population with high risk of Down’s syndrome and high risk of mono-values, and further screening is recommended for pregnant mothers with high risk of mono-values. The most commonly used technique for prenatal diagnosis is amniocentesis, in which a needle is inserted into the amniotic fluid through the pregnant woman’s abdomen under the guidance of ultrasound to extract the amniotic fluid for chromosomal analysis of fetal cells. Amniocentesis is suitable for pregnant women between 18 and 24 weeks of gestation. In addition to amniocentesis, other techniques to perform prenatal diagnosis include chorionic villus biopsy and fetal umbilical vein puncture. If you do not want to do the puncture directly, you can first have a non-invasive genetic test, which can detect common chromosomal number abnormalities (including Down syndrome). Most false-positive Down screening can be ruled out by non-invasive DNA, and then do amniotic fluid or umbilical cord blood puncture if there are problems with the results.