Alpha-fetoprotein is a protein that is produced by unborn children and used during pregnancy to diagnose malformations. It occurs only in very small amounts in the body of adults; a high AFP value is usually an indication of cancer.
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What is Alpha Fetoprotein?
Alpha-fetoprotein (also AFP or alpha-1-fetoprotein) is a protein that is produced in the liver, in the gastrointestinal tract and in the yolk sac of unborn children. It enters the mother’s blood and amniotic fluid through the placenta and urine of the unborn child, where it increases continuously from the 10th week of pregnancy. Elevated values can be an indication of a malformation in the unborn child.
After birth, the AFP value falls with a half-life of 3.5 days and reaches the normal low values for adults. If the AFP value is increased, there is usually a cancer behind it, which is why alpha-fetoprotein is also used as a tumor marker. Tumor markers are the body’s own substances that are increasingly formed in the course of cancer and can therefore be used for the diagnosis and prognosis of diseases.
Alpha-fetoprotein: which values are normal?
To determine the AFP value, a blood sample is taken and examined in the laboratory. In pregnant women, the alpha-fetoprotein is sometimes determined during an amniotic fluid test as part of the prenatal diagnosis.
The reference ranges for normal values of alpha-fetoprotein are given in micrograms per liter (μg / L). Depending on gender and age, they are:
|up to 1 month||< 16.387,0 μg/l||< 18.694,0 μg/l|
|1 to 12 months||< 28,3 μg/l||< 77,0 μg/l|
|12 months to 3 years||< 7,9 μg/l||< 11,1 μg/l|
|3 to 12 years||< 5,6 μg/l||< 5,6 μg/l|
|12 to 18 years||< 4,2 μg/l||< 4,2 μg/l|
|older than 18 years||< 13,4 μg/l||< 13,4 μg/l|
The AFP value increases significantly during pregnancy, the reference ranges for normal values are then:
|Week of pregnancy (SSW)||AFP value|
|15. SSW||< 36,4 μg/l|
|16. SSW||< 41,4 μg/l|
|17. SSW||< 47,0 μg/l|
|18. SSW||< 53,3 μg/l|
|19. SSW||< 60,5 μg/l|
|20. SSW||< 68,7 μg/l|
|21. SSW||< 78,0 μg/l|
When is the AFP value determined?
An alpha-fetoprotein test during pregnancy is used for the early detection of certain malformations in the unborn child. It is carried out as part of the preventive examinations in the second trimester of pregnancy or when there are abnormal ultrasound images.
Outside of pregnancy, the AFP value is determined when certain types of cancer are suspected. The course of such a disease can also be assessed with the help of the alpha-fetoprotein.
When the alpha-fetoprotein is increased
It is perfectly normal for the alpha fetoprotein to rise from the 10th week of pregnancy. However, if the value is unusually high, this can be an indication of a neural tube defect in the unborn child (spina bifida or anencephaly). Even with multiple pregnancies, the AFP value is often higher than normal.
Outside of pregnancy, an increased AFP value can be an indication of one of the following diseases:
If the AFP value is low during pregnancy
Low alpha-fetoprotein between the 10th and 14th week of pregnancy can be an indication of trisomy 21 (Down syndrome) in the unborn child. However, further investigations should always be carried out here in order to confirm or refute the suspicion.
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Source: Lifeline | Das Gesundheitsportal by www.lifeline.de.
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