So, why should pregnant women measure alpha-fetoprotein
1, diagnosis of open neural tube defects. Application of maternal serum in screening neural tube defects Alpha-fetoprotein (afp) is the most common globulin in fetal serum, which is produced by yolk sac in early pregnancy and fetal liver in late pregnancy. In the case of open neural tube defect, afp leaks from the fetus, which significantly increases the afp concentration in maternal serum. Therefore, its role in screening fetal neural tube defects (ntd) is irreplaceable by other markers at present.
The determination of afp content in amniotic fluid can diagnose whether 60%-70% of fetuses have open neural tube defects, and if combined with ultrasound examination, the diagnostic rate of fetal neural tube defects can be significantly improved (up to 92.8%). Through prenatal screening, fetal neural tube malformation can be found early and the birth of deformed children can be reduced. The most common neural tube defects are anencephaly, spina bifida, exposed brain and craniospina bifida. About 80% neural tube defects are accompanied by hydrocephalus.
If the fetus is anencephaly, it can be found that the serum alpha-fetoprotein (afp) is elevated in the second trimester, and the skull is not imaged by B-ultrasound. Screening expectant mothers afp in the second trimester is also helpful to diagnose whether the fetus is spina bifida.
2. Diagnose Down syndrome. The decrease of afp can be seen in Down syndrome, so afp is often used as a detection method for Down syndrome.
3. Understand fetal maturity. Because the afp values in amniotic fluid and expectant mother's serum are related to the gestational age, we can infer the gestational age and understand the maturity of the fetus.
4. Diagnose other diseases. Afp such as stillbirth, congenital esophageal atresia, duodenal atresia, omphalocele, congenital nephrotic syndrome and severe rh blood group incompatibility pregnancy can also be increased.
How to treat the alpha-fetoprotein test sheet?
1. Generally speaking, the normal value of alpha-fetoprotein is less than 20ug/l or 25 ug/L ... However, due to different equipment and methods for detecting afp, the normal reference value of the test results is also different.
2. The normal value of afp in radioimmunoassay: ≤ 25μ g/L; Normal value of afp in radioimmunoassay: ≤ 20μ g/L; The normal value of afp by ELISA: ≤ 25 μ g/L; The most commonly used quantitative detection is radioimmunoassay (normal value is 0 ~ 25ug/l), which is positive when it exceeds 25ug/l, and 25400 when it exceeds 25ug/L..
The low concentration is positive between ug/l, and the high concentration is positive when it exceeds 400 ug/L. ..
3. It is a normal physiological phenomenon that the afp of expectant mothers is lower than 400μg/l at 10- 16 weeks of pregnancy. The higher the value, it may be anencephaly, spina bifida and so on. The lower the value, the higher the risk of Down's syndrome.
4.afp is mainly synthesized in fetal yolk sac and liver, and some of it comes from gastrointestinal tract, kidney and amniotic chorionic cells. The concentration of amniotic fluid is1150-200 of that of fetus.
5. The alpha-fetoprotein value of twins during pregnancy is higher than that of singletons, and the measured 350ng/ml is within the normal range, which is more than three times higher than the normal value for clinical significance. There is a reference value for singleton pregnancy: the average value of 2 1 gestational age is 82.3, the value of triplet is 246.9, and it is meaningful for twins to be above 493. Screening neural tube defects with alpha-fetoprotein is generally not done after 2 1 week of pregnancy. Neural tube malformation can be monitored by B-ultrasound.
The AFP value of pregnant women is definitely higher than normal, so don't worry. Because alpha-fetoprotein is produced in the embryonic stage, after the fetus is born, the content of alpha-fetoprotein in the blood of pregnant women will gradually drop to the normal level.