Alpha fetoprotein

Alpha-Fetoprotein (AFP)

Alpha-fetoprotein (AFP) is a protein produced by the fetus and found in amniotic fluid. It is often used to test for certain birth defects, such as Down syndrome, neural tube defects, and some abdominal wall defects. Other tests may be used with AFP to provide more information.

Preparation

The test is performed on a sample of blood taken from the pregnant woman's arm.

Procedure

• A healthcare professional will clean and tie off the area (usually the arm) where the blood sample will be taken.
• The healthcare professional will insert a needle into the vein, usually in the arm.
• Once the needle is in place, the healthcare professional will draw the blood sample.
• The healthcare professional will remove the needle from the arm.
• The healthcare professional will apply a bandage to the area where the needle was inserted.

Types of AFP Tests

The most common AFP tests used during pregnancy are:

• Maternal serum AFP (MSAFP): This test measures the level of AFP in the mother's blood.
• AFP quadruple screen: This test measures levels of AFP, unconjugated estriol, human chorionic gonadotropin, and inhibin A in the mother's blood.
• AFP integrated screening: This test measures the levels of AFP, unconjugated estriol, and human chorionic gonadotropin in the mother's blood.
• Fetal AFP: This test measures the level of AFP in the amniotic fluid.

Risks

The risks associated with an AFP test are minimal. There is a small risk of mild bruising at the site where the blood sample was taken. In rare cases, a faint scar may develop at the site of the needle insertion.

When to Consider an AFP Test

AFP tests are typically performed during the second trimester of pregnancy, between 15 and 22 weeks. The test is recommended for all pregnant women, but may be especially important for women who are over age 35, who have had a previous child with a birth defect, or who have certain medical conditions.

Why an AFP Test is Performed

AFP tests are used to screen for certain birth defects, such as Down syndrome, neural tube defects, and some abdominal wall defects. They can also help to identify multiple pregnancies, such as twins or triplets, and can provide information about the baby's development and health.

Interpreting Results

The results of an AFP test may be misinterpreted. For example, a low AFP result may be interpreted as a sign of a neural tube defect when in fact the baby may not be affected. Similarly, a high AFP result may be interpreted as a sign of a chromosomal abnormality when the baby may not actually have one. It is important to consult with a healthcare provider about the results of the test.

Follow-Up Care

If the results of an AFP test indicate a concern for a birth defect, additional tests may be recommended to confirm the diagnosis. Follow-up care may include scans, ultrasounds, and genetic counseling.