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AFP

Alpha-fetoprotein Screening (AFP)/Enhanced AFP

By Sharon Waldrop

Beginning in the early 1980s, pregnant women were offered Alpha-fetoprotein (AFP) screening to detect neural tube defects such as spina bifida (open spine) as well as Down syndrome. In the late 1980s the test was enhanced to also measure the levels of two pregnancy hormones: estriol and human chorionic gonadotropin (HCG). This new and improved test is commonly known as the Enhanced AFP, AFP3, or a triple screen.

The screening is done 16 to 18 weeks after the last menstrual period. The test is routine and poses no threat to Mother or Baby. Blood is drawn from the mother's arm and sent to a laboratory for testing. Results are normally available in one week, depending on the laboratory used.

Maternal serum Alpha-fetoprotein (MSAFP) is produced by the liver of the fetus and enters the mother's bloodstream. Elevated levels of MSAFP may mean a neural tube defect or absence of all or part of fetal brain material, otherwise known as anencephaly. Triple screening can diagnose a high percentage of anencephaly and spina bifida cases. A low level of MSAFP could be an indication of Down syndrome; however, an AFP screen is not as accurate as an amniocentesis or chorionic villus sampling (CVS) in detecting Down syndrome, according to Dr. R. Harold Holbrook, Jr., of Stanford University. Only an amniocentesis or CVS screen can definitely diagnose or exclude Down syndrome. An AFP test can show a risk of an abnormality, not a diagnosis.