Also called fetuin, thealpha-fetoprotein is a protein naturally produced by yolk sac and liver du fetus in development. It is found in fetal and maternal blood (during pregnancy). In newborns, its rate decreases a few weeks after birth.

In adults, alpha-fetoprotein can reappear during certain diseases, most of the time hepatic or tumor.

Alpha-fetoprotein analysis may be prescribed for a woman during pregnancy or for adults outside of pregnancy.

During the pregnancy, alpha-fetoprotein analysis is used for prenatal diagnosis of various abnormalities and is performed in the second trimester. The test is usually most accurate between the 16th and 18th weeks. Analysis of alpha-fetoprotein occurs concurrently with that of the human chorionic gonadotropic hormone (HCG), estriol and inhibin A, placental hormones. The goal is in particular to detect a malformation of the neural tube (which will become the nervous system) of the fetus, such as Spina bifida, but also chromosomal abnormalities, such as the risk of trisomy 21 (or Down’s syndrome).

In adults (outside pregnancy), alpha-fetoprotein analysis can be performed to diagnose liver problems or to detect certain cancers.

The analysis of alpha-fetoprotein consists of a blood test at the level of a vein and does not require any specific preparation. The doctor places a tourniquet on the patient’s front arm, about 10 cm above the site where the venipuncture will take place, usually at the crease of the elbow.

In pregnant women, part of the alpha-fetoprotein produced by the fetus passes into the maternal blood, and therefore no amniotic or fetal sampling is required. The blood sample is taken in a “classic” way.

In adults, men and women outside the period of pregnancy, the normal amount of alpha-fetoprotein is less than 10 ng / ml of blood.

An increase in the level of alpha-fetoprotein in the blood may reveal:

• liver disease, such as cirrhosis, for an liver cancer, the alcoholic hepatitis or to viral hepatitis

• un cancer testicles, ovaries, stomach, pancreas or bile ducts.

In pregnant women, in the second trimester, the alpha-fetoprotein level is usually between 10 and 200 ng / ml. Elevated alpha-fetoprotein levels can cause:

• a neural tube defect in the developing fetus: Spina bifida, anencephaly

• a neurological malformation

• hydroencephaly

• a malformation of the esophagus or kidneys

Conversely, a low level can be a sign of a chromosomal abnormality such as Down syndrome (trisomy 21).

Be careful, however, the alpha-fetoprotein level varies during pregnancy. It is therefore important to know precisely the stage of pregnancy at which the woman is during the test. Abnormal alpha-fetoprotein results may also be due to multiple pregnancy or fetal death.

Additional tests are therefore necessary in the event of abnormal alpha-fetoprotein levels, such as an ultrasound or amniocentesis (removal of the amniotic fluid surrounding the fetus).