Alpha-fetoprotein screening is a blood test that checks the level of alpha-fetoprotein in the mothers' blood during pregnancy. AFP is a protein normally made by the baby’s liver. It is found in the fluid surrounding the baby in the womb (amniotic fluid). AFP goes through the placenta into the mother's blood. The AFP blood test is called MSAFP (maternal serum AFP). The AFP can also be measured in the amniotic fluid, called AFAFP.
Too much or too little AFP may be a sign of:
- Open neural tube defects (ONTD), such as spina bifida
- Down syndrome
- Other chromosomal abnormalities
- Defects in the abdominal wall of the baby
- Twins (more than one baby is making the protein)
- A miscalculated due date, as the levels change during pregnancy
You may have an AFP test as one part of a two-, three-, or four-part screening. This is sometimes called a multiple marker screen. The other parts of the test may check for these hormones made by the placenta:
- hCG (Human chorionic gonadotropin hormone),
- Estriol, and
Abnormal test results for AFP and other markers may show a need for more testing. An ultrasound can usually confirm the dates of the pregnancy. It is also used to look at the baby’s spine and other body parts for defects. An amniocentesis may be needed for accurate diagnosis.
Alpha-fetoprotein testing details
In most cases, an alpha-fetoprotein test is done in the following steps:
- Blood is usually taken from a vein between the 15th and 20th weeks of pregnancy.
- The blood sample is then sent off to be checked at a laboratory.
- Results of the tests are usually ready in 1 to 2 weeks or less, depending on the laboratory.
Risks and benefits of alpha-fetoprotein screening
There are no risks of having the actual alpha-fetoprotein test performed other than the usual risks of a blood test. A multiple marker screening test is not diagnostic. This means it is not 100 percent accurate. It is only a screening test to see who might need more tests for their pregnancy. There can be false-positive results. These results show a problem when the baby is actually healthy. False negative results show that everything is OK when the baby actually does have a health problem.
The benefits of the alpha-fetoprotein is there is an ability to find out which women have a higher risk of having a baby with a birth defect. It is also used to find the women who need additional testing during pregnancy. Without the AFP test, some women would be given additional testing.
If you have questions regarding alpha-fetoprotein screening, call (314) 996-5433 or email us to speak with a doctor.