Alpha-Fetoprotein

Alpha-Fetoprotein is measured in a blood sample

Alpha-fetoprotein is a protein that is found and made in the liver and yolk sac of an embryo and the intestinal tract of a foetus.

The level of alpha-fetoprotein (AFP) in the amniotic fluid surrounding the foetus in the uterus can be measured to monitor the progress of a pregnancy. The normal values are: –

Weeks of pregnancy Lower limit Upper limit
14 14 55
15 15 61
16 17 69
17 20 81
18 23 94
19 26 106
20 30 122
21 36 143
Term >50

A slow decrease in values indicates a normal pregnancy. On the other hand, a steady rise indicates foetal distress, defect of spinal development (neural tube defect), kidney disease (eg. nephrotic syndrome), or twins. Very low levels may be found if the foetus has Down syndrome.

Alpha-fetoprotein levels can also be measured in blood for the same reasons as above, plus assessment of liver diseases and cancer of the ovary and testes. The normal level starts at less than 12 µg/L. and rises throughout pregnancy up to 50 µg/L or more at full term.

Very high blood levels may indicate Down syndrome (trisomy 21) or a neural tube (spinal cord) defect in the foetus.

A high level can occur with liver cancer (hepatic carcinoma), bowel cancer (colon carcinoma), stomach cancer, hepatitis, liver cirrhosis, other liver diseases, ovary cancer (teratoma) or testicular cancer. A steady rise occurs throughout a normal pregnancy, but a drop in levels late pregnancy indicates foetal distress. Excess blood levels in a non-pregnant adult indicates serious disease.

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