When you get the Down’s syndrome screening report, are you often confused about what AFP and HCG stand for, and what the OD and MOM values mean respectively? What does trisomy 21 risk mean? What is trisomy 18 risk and trisomy 13 risk? What do all these values represent? Now I’m going to teach you how to read your Down’s syndrome screening report card. (1) AFP (alpha-fetoprotein) AFP is a fetal-specific globulin with a molecular weight of 64,000 to 70,000 daltons that may have immunomodulatory functions as a glycoprotein during pregnancy and may prevent fetal rejection 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 be synthesized by the fetal digestive tract to enter the fetal blood circulation. AFP in amniotic fluid mainly comes from fetal urine, and its trend is similar to that of fetal blood AFP. Maternal blood AFP comes from amniotic fluid and fetal blood, but the trend is not consistent with that of amniotic fluid and fetal blood. The concentration of maternal blood AFP is lowest in the early stage of pregnancy, and gradually increases with the progress of pregnancy, reaching a peak at 28-32 weeks of gestation, and then decreasing. In pregnant women with congenital fetuses, the serum AFP level is 70% of that of normal pregnant women, i.e. the average MoM value is 0.7-0.8 MoM. Free – subunit – chorionic gonadotropin In pregnant women with congenital fetuses, the serum Free hCG? level is tonicly elevated, with an average MoM value of 2.3-2.4 MoM. In fact, the MOM value of free – hcg is high. People need not be too nervous. About: hCG is a human chorionic gonadotropin synthesized by placental cells and consists of two subunits, a- and b-. hCG exists in two forms, intact hCG and separate b-chain. Both types of hCG are active, but only hCG present in the b-single chain form is the specific molecule for the assay. hCG enters the mother’s blood right after fertilization and proliferates rapidly until the 8th week of pregnancy, then slowly decreases in concentration until the 18th to 20th week, and then remains stable. The MOM value is a ratio of the value of the marker in a pregnant woman divided by the median value of a normal pregnant woman at the same gestational week, which is the MOM. The values must therefore be converted into a multiple of the median (MOM) to “standardize” them and facilitate clinical judgment. For example, the value of free-HCG in a random pregnant woman at 14 weeks + 0 days: 28800mIU/ml The median value at 14 weeks + 0 days is: 14400mIU/ml The MOM of this pregnant woman is: 28800/14400=2, so if this indicator fluctuates, do not pay too much attention to it, it may also be caused by inaccurate calculation of the time of pregnancy, there is really no need to put yourself in a panic. There is no need to put yourself in a panic. (3) About trisomy 21, 18 and 13 Normally, there are 46 pairs of 23 chromosomes in human, and trisomy 21, 18 and 13 are the 21st, 18th and 13th pairs of chromosomes of the fetus, which are one more than the normal two, and are called trisomy XX. One of them is trisomy 21, which is Down syndrome. Pregnant women of any age may carry a fetus with chromosomal abnormalities, but the incidence of chromosomal abnormalities increases significantly with the age of the pregnant woman, for example, the chance of chromosomal abnormalities among pregnant women under 25 years old is 1:1185, while at 25 years old it is as high as 1:335, so senior pregnant women over 25 years old need to have chromosomal screening. 1. Down’s syndrome screening is a possibility test: the high-risk group only means that the fetus is more likely to be a Down’s child, and the low-risk group may also be a Down’s child. 2. About 1/10 of all pregnant women are screened as high-risk group, and 1~2/100 of the high-risk group are Down’s children, which means that 1~2/1000 of pregnant women are Down’s children. 3. The normal value is about 1/700. The international standard is 1/2704, and the Down’s syndrome screening value is a modified value. The factors that affect the value of Down’s syndrome screening are: the age of the pregnant woman, the week of pregnancy, the fetal alpha protein secreted by the fetus, the human chorionic hormone secreted by the placenta, drug factors, genetic factors, etc. The Down’s syndrome screening value may be affected by the use of “Dolly’s mother” during pregnancy preservation, which makes the human chorionic hormone exceed the normal value.