Definition of Alpha fetoprotein:

Alpha fetoprotein (AFP) is a protein normally produced by the liver and yolk sac of a fetus. AFP levels decrease soon after birth. AFP probably has no normal function in adults.

A test can be done to measure the amount of AFP in your blood.

See also: Quadruple screen

How the test is performed:

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test:

There is no special preparation.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

Your doctor may order this test to:

• Screen for problems in the fetus during pregnancy
• Diagnose certain liver disorders
• Screen for and monitor some cancers

During pregnancy, this AFP test can be done along with the examination of amniotic fluid (amniocentesis) to help detect fetal spina bifida or other birth defects.