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Procedure: Alpha-Fetoprotein Test

Description and Purpose

Alpha-Fetoprotein (AFP) or foetal alpha globulin , released by the baby's liver, is present in the mother's blood. Abnormally high AFP levels may signal abnormalities including neural tube defects (such as spina bifida), kidney problems, malformations of the digestive tract, threatened miscarriage , or death of the foetus. Abnormally low AFP levels may indicate Down syndrome , but this diagnosis must be confirmed by other tests.

Preparation and Procedure

The test is usually performed between the 15th and 18th weeks of pregnancy and is performed on a blood sample. Sometimes the AFP test can be combined with an analysis for human chorionic gonadotropin (hCG) and unconjugated estriol. This is termed triple screening . All 3 substances, which are produced by the foetus and enter the mother's blood stream, indicate an increased risk for Down syndrome, spina bifida, and other significant birth defects , and of premature labour and other third-trimester complications.
It should be noted that these tests can't be used to diagnose these conditions, but helps identify foetuses of younger women at risk and, thus, indicates if more definitive testing, such as amniocentesis or chorionic villi sampling , is necessary.

The information in this page is presented in summarised form and has been taken from the following source(s):
1. The Yale University School of Medicine Patient's Guide to Medical Tests, Barry L. Zaret M.D., Senior Editor, published by Houghton Mifflin. Online:

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Contact Last modified: Oct 20 2004