Alpha-fetoprotein blood (AFP) test during pregnancy
Unborn babies usually produce
alpha-fetoprotein (AFP) and it appears in their mother's blood. Checking a
mother's AFP levels can show if her baby has problems with the neural tube that
will become the brain and spinal cord.
AFP is one of the blood tests
you do in a triple or quadruple screen. You can choose whether to take an AFP
test or not. A genetic counselor can help you make a decision.
How it's done
You do a maternal serum AFP
test when you are about 4 months pregnant.
The technician uses a needle
to take a small sample of blood from a vein in your arm or forearm. You may
feel a small prick on your skin and some bruising or bleeding where the needle
was inserted. They will then send your blood to a laboratory.
What the results mean
A negative or normal test
usually means that your child does not have any genetic abnormalities.
A positive test with high AFP
levels suggests a birth defect such as spina bifida. This is usually a result
that is 2.5 times or more the "average" AFP level you would expect to
see at this point in your pregnancy.
A positive test with low AFP
levels could indicate a problem such as Down syndrome or Edwards syndrome.
Don't worry if your test is
not normal. AFP only tells you that there is a risk of a problem, not that
there is one.
A high AFP level may mean that
you are further along than you thought, as your levels continue to rise
throughout your pregnancy. Your baby may be producing more AFP than usual, or
you may be having twins. Other factors, including your race, weight, and
diabetes, may also affect your score.
What will happen next
Sometimes you can get a false
positive result. This means that the test shows that something is wrong when it
is not. Your doctor will probably want to recheck your results. Another test
often shows that your child is healthy.
When your AFP is too high or
too low, you may have other tests to find out why.
Your doctor will likely do an
ultrasound to confirm how long you have been pregnant and how many children you
have. They will also closely monitor for birth defects.
One of the next steps may be
to determine if there is AFP in the fluid around your baby with a test called
amniocentesis. Your doctor uses a long, thin needle to insert through the
abdomen into the amniotic sac and remove a small amount of fluid for laboratory
testing.
You may need to speak with a
genetic counselor who can help you understand your results and answer your
questions.
If your baby is born too soon,
your doctor will monitor you closely.
If tests show that your child has a birth defect or other problem, you will have to make some difficult decisions. Talk to a specialist about what to expect and your options so you can make the best choice for your family.