This article forms part of our ‘Tests and results’ series for 2011 which aims to provide information about common tests that general practitioners order regularly. It considers areas such as indications, what to tell the patient, what the test can and cannot tell you, and interpretation of results.
Antenatal screening is performed in the first or second trimester to determine whether a pregnant woman’s baby has an increased risk of having Down syndrome (a chromosomal abnormality affecting one in 500 pregnancies), Edward syndrome (one in 3000) or open neural tube defects (one in 750). First trimester screening combines results from a blood test with a nuchal translucency and nasal bone obstetric scan during the first trimester of pregnancy. Second trimester screening requires only a blood test. The screening approach varies across Australia; this article primarily describes the Victorian protocol.
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