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Your AFP Triple Screen is a blood study for detecting
two types of birth defects in the unborn baby. These are neural tube defects
(including anencephaly, spina bifida "open spine", and related conditions) and
Down syndrome (Mongolism), a cause of mental retardation and other physical
problems. There are two drawbacks to any screening test: there will by
definition be a large number of false positive screens (the test may indicate a
potential problem when it does not actually exist) and there will be a certain
number of false negatives. For example, the AFP Triple Screen will identify
80%, but miss 20%, of cases of Down syndrome.
The AFP Triple Screen
check for three serum markers: Aiphafetoprotein (AFP), human chorionic
gonadotropin (HCG), and unconjugated estriol (UE3). These three values are then
entered into a computer along with the patient's chronological age and the
gestational age of the pregnancy. The computer program then assigns a risk
factor for both Down syndrome and neural tube defects. If the risk is less than
1 in 200 it is generally considered a negative screen; if it is greater than 1
in 200 the screen is positive. Further studies (usually ultrasound and
amniocentesis) could then be performed by the specialists at either UNC or Duke
to determine if the fetus is indeed affected. The degree of any abnormality
present would be useful in deciding whether to continue the pregnancy, making
special arrangements for delivery and beyond, or to pursue termination.
If you have a possible family history of these birth defects or have
had a baby who is affected, this screening is encouraged. The American College
of Obstetricians and Gynecologists recommends that it be offered to all
obstetrical patients. It can be drawn any point from 15 to 20 weeks of
pregnancy, but the best time is about 16 weeks.
You will need to give
written permission for this blood test to be done, and should also understand
that it does not detect all birth defects, chiefly neural tube defects and
Down syndrome. The test is elective and only you can decide whether or not
it should be done. You should also be aware that not all health insurance plans
will pay for AFP Triple Screening. If your insurance does not cover this test
your are expected to pay for it yourself if you wish it to be carried out. By
your signature below you understand, accept, and agree to these provisions of
the AFP Triple Screen and will pay for the test if it is declined by your
insurance carrier.
I wish to accept________ reject________ the AFP
Triple Screen Test.
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