The alpha fetoprotein (AFP) test

The alpha fetoprotein (AFP) test is a blood test done on the motherto-be. Alpha-fetoprotein is produced in the baby's liver, and it passes in small quantities into your bloodstream. Measurement of the amount of alpha-fetoprotein in your blood can help your doctor predict problems in your baby, such as spina bifida or Down syndrome. (APP detects only about 25% of Down syndrome cases. If Down syndrome is indicated, additional detailed diagnostic tests will probably be ordered.)

At this time, AFP is not performed on all pregnant women but is required in some states, including California and New York. If the test is not offered to you, discuss it with your doctor.
The test is usually performed between 16 and 20 weeks of pregnancy. Test results must be correlated with the mother's age and weight, and the gestational age of the fetus. If APP detects a possible problem, more definitive testing is usually ordered.

What the Test Can Detect
APP can detect the following:
•    neural-tube defects
•    severe kidney or liver disease
•    esophageal or intestinal blockage
•    Down syndrome
•    urinary obstruction
•    osteogenesis imperfecta (fragility of the baby's bones)


False Positive Results

One problem with the AFP test is a high number of false-positive results; that is, the results say there is a problem when there isn't one. Currently, if 1,000 women take the AFP test, 40 test results come back as "abnormal." Of those 40, only one or two women actually have a problem. If you have an AFP and your test result is abnormal, don't panic.
You'll take another AFP test and have an ultrasound. Results from these second tests should give you a clearer answer.

Be sure you understand what "false-positive" and "false-negative" test results mean. Ask your doctor to explain what each result can mean to you.