Maternal Serum Alpha-Fetoprotein (MSAFP) or AFP or Triple Screen

October 6, 2011

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The Maternal serum alpha-fetoprotein test is a blood test which checks for the possibility of certain genetic defects. It is generally performed between 15 and 22 weeks of pregnancy.

If your test is abnormal, you will likely receive an ultrasound in order to confirm how far along you are in your pregnancy. Your test will then be repeated and if abnormal you may be referred to genetic counseling, or your health care provider may suggest an amniocentesis.

This test is made up of three components, the Maternal serum alpha-fetoprotein (MSAFP), which tests the levels of alpha-fetoprotein (AFP) in your blood, Human chorionic gonadotropin (HCG) test, which measures the pregnancy hormone HCG, and Estriol test, which is an estrogen test.

The MSAFP evaluates the levels of alpha-fetoprotein (AFP) in your blood. The MSAFP test is generally offered between 15 and 22 weeks of gestation.

As your baby grows, it’s liver produces the protein AFP. Small amounts of this protein cross through the amniotic fluid and the placenta and into the pregnant woman’s bloodstream.

Elevated levels of AFP can indicate possible problems with the fetus such as spinal abnormalities or neural tube defects like spina bifida and chromosomal disorders like Down syndrome.

The AFP screening is a simple test which tells you the probability of your baby having neural tube or chromosomal disorders. It cannot tell you whether or not your baby actually has one of these conditions.

If an AFP screening shows that there could be a problem, your health care provider will generally order an amniocentesis or an ultrasound.

Approximately 5 percent of AFP screenings produce an abnormal result, even when the fetus is healthy. This is generally due to a miscalculation of the gestational age of the fetus or the presence of twins. If you are later in your pregnancy than you thought, your blood will contain higher levels of AFP than expected. If you are earlier in your pregnancy than you thought, your blood will contain lower levels of AFP than expected. This can cause inaccuracies in your results.

Problems with the placenta, your age, weight, race, and type 1 diabetes can cause abnormal levels of AFP.

Of the pregnancies showing abnormal AFP levels, only 2-3 percent result in birth defects.

The triple test can detect Down syndrome 60-70 percent of the time, with a false positive test result rate of 5 percent. The MSAFP test can detect spina bifida with 80 percent accuracy and anencephaly with 90 percent accuracy.

If you are planning to do an amniocentesis, an AFP test is generally considered unnecessary.

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