What is alpha-fetoprotein screening?
Alpha-fetoprotein screening is a blood test for pregnant women. It can be used to look for a problem in the baby’s spine or certain other conditions, such as some chromosome problems.

The test measures the level of a protein called alpha-fetoprotein (AFP) in your blood. AFP is produced by your unborn baby’s liver. Some AFP passes from the baby into your bloodstream. If a baby has certain problems, the level of AFP may be abnormally high or low. Sometimes, however, the AFP level is abnormal when the baby has no problems. Because the test is not completely accurate, your health care provider will usually order other tests if the AFP levels are high or low.

How is the test performed?

A small amount of blood is taken from your arm between the 15th and 18th weeks of pregnancy. For the test to be interpreted properly, you and your health care provider need to be sure of your due date. Alpha-fetoprotein levels are highest between 15 and 18 weeks of pregnancy. After this time they slowly decrease.

It is important to have the test at the right time in your pregnancy. If the AFP level is higher or lower than normal, enough time must remain in your pregnancy for further steps. These steps might include more tests and counseling.

What conditions does the test find?

A high level of AFP may indicate a problem with the spinal cord, brain, or digestive system. Examples of problems that can cause a high AFP are:
spina bifida (the spine has not closed normally), kidney problems, severe skin problems, severe chromosome problems (other than Down syndrome), anencephaly (all or part of the brain is missing), a failure of your baby’s abdomen to close, so that the intestines are enclosed in a sac outside the abdomen, a defect in the esophagus (food pipe).
A low level of the protein may indicate Down syndrome.

Other possible causes for abnormal levels are:
* an incorrect due date
* the presence of more than 1 baby
* miscarriage
* a pulling away of the placenta from the uterus
* a baby who is smaller than normal
* an overweight mother, especially if the mother is African American
* diabetic mother

How accurate is the test?

The test is not completely accurate. A baby may have a defect even though AFP levels are normal. Or a baby may be quite normal even though AFP levels are abnormal. Usually, if the first blood test shows normal levels, no further tests are done. If the first test shows abnormal levels of AFP, it may be repeated before other tests are done.

For every 1000 pregnant women tested, about 50 have abnormal test results. Of these 50, just 1 or 2 with high AFP levels have babies with problems. The test finds 90% of babies with anencephaly and 75% with spina bifida.

A test called a triple or quad screen has been developed to provide more accurate screening for birth defects. In addition to AFP, your blood is tested for 2 or 3 other substances produce by the placenta. These substances are human chorionic gonadotropin (HCG), unconjugated estradiol (uE), and dimeric inhibin-A (DIA).

Who should have this test?

All pregnant women should be offered AFP screening. You should have the test if:
* You will be 35 or older when the baby is due.
* You have a personal or family history of birth defects.
* You used or were in contact with possibly harmful medicines or drugs at the time you became pregnant.
* You have diabetes.
* An ultrasound scan shows a problem with the baby’s development.
* You or the baby’s father has a chromosome problem.

What happens if the results are abnormal?

Abnormal results indicate the need for further tests, such as:
* ultrasound scans (a scan of your uterus and the baby with sound waves)
* amniocentesis (a test of the fluid around the baby) to look at the baby’s chromosomes.

In some cases these tests find no reason for abnormal AFP results.

Talk to your health care provider about your results and ask questions. Ask if and when you need more tests. If the results of the AFP test and follow-up tests show that your baby does have a serious problem, your provider will talk to you about your choices of treatment.

What are the risks of AFP testing?

There is virtually no risk to you or your baby from this test.

What are the benefits?

Most often, the test reassures you that your baby probably does not have a serious defect.

Abnormal results can help you and your health care provider manage your pregnancy better. Some problems can be treated with surgery while the baby is still in the uterus. If a brain or spinal defect is diagnosed, you and your health care provider can discuss your options. Your provider may plan your delivery in a center equipped to deal with these defects, which may improve the outlook for your baby.

Your provider can offer you counseling to help you prepare for the baby’s problems. There are also many support groups for families who have children with birth defects.

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. © 2005 McKesson Corporation and/or one of its subsidiaries. All Rights Reserved.