What do the test results mean?

An elevated AFP level in the blood of a pregnant woman may be caused by a fetal abnormality. However, the AFP is only a screening test. It can show false positive and false negative results. The test can be inaccurate, for example, if the pregnancy dates are wrong. AFP values are also higher if the woman is carrying more than one baby. A fetus that is in trouble or has died can also elevate the level of AFP.

Because so many things can increase the level of AFP in pregnancy, a woman who has an elevated AFP may have further testing. This may include pregnancy ultrasound. Ultrasound is a special X-ray test that uses sound waves to see the baby. The healthcare provider may also recommend an amniocentesis. In this procedure, a needle is inserted into the amniotic fluid through a small hole in the woman's abdomen. This test can further define any problems with the fetus.

A low AFP level in a pregnant woman may mean that the fetus has Down syndrome. A test called the triple screen can further measure the baby's risk for Down syndrome. The mother's blood is tested for AFP, HCG (the pregnancy hormone), and estriol. These three values are combined in a formula that indicates the probability of the baby having Down syndrome.

In an adult who is not pregnant, the AFP level is elevated with certain cancers. These include:

If someone has a known cancer that causes increased AFP, the AFP level can be monitored during treatment. If the AFP level goes down with treatment, the cancer is probably shrinking. If the level goes up, the cancer is probably growing larger.

The AFP level can also be increased by conditions other than cancer. Liver diseases, such as hepatitis, can elevate the AFP level. Bowel inflammations, such as colitis, can cause a higher AFP level.