It is understood that Down screening during pregnancy is a very important test, so what is Down screening? Sweetheart will teach you how to understand the Down screening report, let’s take a look!
(1)afp (alpha-fetoprotein)
afp is a specific globulin of the fetus, with a molecular weight of 64,000-70,000 daltons. It may have an immune regulatory function of glycoprotein during pregnancy, which can prevent the fetus from being rejected by the mother.
aFP is synthesized by the yolk sac at 1-2 months of the early pregnancy, and is mainly synthesized by the fetal liver. The fetal digestive tract can also synthesize a small amount of afp into the fetal blood circulation. The fetal blood AFP value increased rapidly at the 6th week of pregnancy and reached its peak at the 13th week of pregnancy. After that, as the pregnancy progresses gradually declined to full term, the AFP in amniotic fluid mainly comes from fetal urine, and its change trend is similar to that of fetal blood AFP. The maternal blood AFP comes from amniotic fluid and fetal blood, but it is not consistent with the change trend of amniotic fluid and fetal blood. In the early stage of pregnancy, the concentration of maternal blood AFP is the lowest, which gradually increases with the progress of pregnancy. It reaches its peak at 28-32 weeks of pregnancy and then decreases later.
The serum AFP level of pregnant women with congenital foetus is 70% of that of normal pregnant women, that is, the average mom value is 0.7-0.8 mom.
(2)freehcgβ (free-β subunit-chorionic gonadohormone)
Pregnant women with congenital silly fetus have ankylosing levels of freehcgβ, with an average mom value of 2.3-2.4 mom.
In fact, the mom value of free-hcg is too high.
About: hcg is a human chorionic gonadotropin synthesized by placental cells, consisting of two subunits a- and b-. hcg exists in two forms, complete hcg and separate b-chain. Both HCGs are active, but only HCGs in the b-single-stranded form are the specific molecules assayed. After fertilization, hcg enters the maternal blood and proliferates rapidly until the 8th week of pregnancy, then slowly reduces the concentration until the 18th week to 20th week, and then remains stable.
and mom value is a ratio, that is, the detection value of markers in pregnant women divided by the median value of normal pregnant women in the same pregnancy week, which is mom. Since the level of prenatal screening will vary greatly with the increase of gestational week, its value must be converted into a multiple of the median (mom) to express it to "standardize" and facilitate clinical judgment.
For example: Random pregnant women with 14 weeks and 0 days gestational week: 28800miu/ml
The median pregnant women with 14 weeks and 0 days gestational week: 14400miu/ml
The mom of this pregnant woman: 28800/14400=2, so if this indicator fluctuates simply, don’t pay too much attention. It may also be caused by inaccurate calculation of the time of pregnancy, so there is no need to panic. (3) Questions about trisomy 21, 18, and 13
Under normal circumstances, people have 46 23 pairs of chromosomes. Trisomy 21, 18, and 13 are the 21st pair, 18th pair, and 13th pair of the fetus. There is one more chromosome than the normal two, which is called trisomy xx. Among them, Trisomyces 21 is Down syndrome. How to find abnormal chromosomes＞＞
Pregnant women of any age may conceive a fetus with chromosome abnormalities, but the incidence of chromosome abnormalities increases significantly with the age of pregnant women. For example, the probability of chromosome abnormalities in pregnant women under 25 years old is 1:1185, while at the age of 25, it is as high as 1:335, so pregnant women over 25 years old need to undergo chromosome examination.
1. Down's screening is a possibility test: high-risk people just say that the fetus is more likely to be Down's children, and low-risk people may also be Down's children
2. About 1/10 of all pregnant women screening is a high-risk group, and 1 to 2/100 of the high-risk people are Down's children, that is, 1 to 2/1000 of the pregnant women are Down's children
3. When the blood test screening value is greater than 1/270, it is a high-risk group, and the normal value is about 1/700. The international standard is 1/270
4, and the Down screening value is the corrected value. The main factors affecting the Down screening value are: age of pregnant women, gestational week, fetal alpha protein secreted by the fetus, human vesicle secreted by the placenta, drug factors, genetic factors, etc. Taking "Dolly Mom" during pregnancy can cause human vesicular hormone to exceed normal values may affect Down's screening value.
(3) To determine whether the fetus is a Down child, the only way to do amniotic fluid penetration is to do amniotic fluid penetration
amniotic fluid penetration: extract amniotic fluid, cultivate cells that the fetus falls off in amniotic fluid, and test the chromosomes of the cells (test the chromosome 21 of the fetus).
Draw amniotic fluid: Take 20ml of amniotic fluid, the risk is possible infection, amniotic fluid leakage, miscarriage, and miscarriage (probability 1/1000)
Cultivate the cells that have fallen out of the fetus in amniotic fluid, with a success rate of 98/100.
tests the chromosomes of cells (tests the chromosomes 21 of the fetus). Accuracy rate is 100/100.
For Down’s screening, pregnant mothers should pay more attention to this test. If you have any questions about this, you should communicate more with the doctor!
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