Definition of Maternal serum alpha-fetoprotein (MSAFP)

Maternal serum alpha-fetoprotein (MSAFP):

The presence of alpha-fetoprotein (AFP) , a plasma protein normally produced by the fetus, in the mother's blood. MSAFP serves as the basis for some valuable tests.

Alpha-fetoprotein (AFP) is a plasma protein that is normally produced by the fetus. It serves as the basis for some valuable tests.

Alpha-fetoprotein is manufactured principally in the fetus's liver and gastrointestinal (GI) tract besides the yolk sac, a structure temporarily present during embryonic development.

The alpha-fetoprotein level is typically high in the fetus's blood. It decreases in the baby's blood after birth. And by one year of age, it is virtually undetectable.

During pregnancy, alpha-fetoprotein crosses the placenta from the fetal circulation and appears in the mother's blood. The alpha-fetoprotein level in the mother's blood (the maternal serum alpha-fetoprotein) provides a screening test for several disorders including:

  • Open neural tube defects (anencephaly and spina bifida); and
  • Down syndrome (and other chromosome abnormalities).

The maternal serum alpha-fetoprotein (MSAFP) tends to be:

  • High with open neural tube defects such as anencephaly and spina bifida (meningomyelocele); and
  • Low with Down syndrome (trisomy 21, an extra chromosome number 21).

Alpha-fetoprotein production is essentially zero after a year of age. However, it increases again under the stimulus of some liver diseases. It may, for example, be produced by viral hepatitis and cirrhosis of the liver. Alpha-fetoprotein is also made by primary liver tumors (hepatomas) and by germ cell tumors (teratocarcinoma and embryonal cell carcinomas). A person's serum alpha-fetoprotein level can therefore be used to help detect these conditions and monitor their cirrhosis of the liver. Alpha-fetoprotein is also made by primary liver tumors (hepatomas) and by germ cell tumors (teratocarcinoma and embryonal cell carcinomas). A person's serum alpha-fetoprotein level can therefore be used to help detect these conditions and monitor their treatment.

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Last Editorial Review: 9/20/2012

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