Screening and diagnostic tests
Screening
tests assess your risk of having a baby with a chromosomal abnormality such as Down syndrome or a neural tube defect such as
spina bifida, but they don’t provide a
definite diagnosis.
Because screening tests aren’t invasive, and carry no risk
of miscarriage, they’re normally the first step that pregnant women take.
Screening
tests include ultrasound scans, such as the nuchal translucency scan which is performed as part of
your first trimester screen at around 11-13 weeks and checks for signs of Down
syndrome; and blood tests, carried out at 15-20 weeks to check for neural tube
defects. These tests will tell you your statistical risk of having a baby with
a particular problem. If you’re ‘screen negative’ this means that the risk of
having a baby with this problem is low enough not to be considered a problem;
if you’re ‘screen positive’, you’re considered to be at a high enough risk to
have a diagnostic test.
It’s
important to recognize that being ‘screen positive’ doesn’t mean your baby is
definitely affected by this condition. Many of the women who get positive
results go on to have perfectly healthy babies. These cases are referred to as
false positives.
Diagnostic
tests are able to tell you for sure whether your baby has a certain condition.
They include certain types of ultrasound scans, CVS (chorionic villus sampling) and amniocentisis and chorionic villus sampling.
These tests are invasive and carry a small risk of miscarriage that, for some
women, outweighs the benefit of being tested.
The information in this feature is intended for
educational purposes only. If you have any concerns about your health, the
health of your child or the health of someone you know, please consult with a
doctor or other healthcare professional.
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Last Modified: 20/06/2007
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