Screening during pregnancy: Down’s syndrome

Down’s syndrome is associated with moderate to severe learning disability and a spectrum of other health problems. Down’s syndrome can vary in degree of severity, and many people with this condition lead fulfilling lives. Older mothers are more likely than younger mothers to conceive a child with Down’s syndrome. However, the majority of Down’s syndrome babies are born to younger women as this is when most women have babies. 

What are the screening tests for Down's Syndrome?

The screening tests which may detect this condition are a nuchal translucency scan or the early screening test for Down’s syndrome.

  • Both are carried out at 11-13 weeks of pregnancy or at a later screening test for Down’s syndrome carried out at 15-20 weeks.
  • The ultrasound scan measures the thickness of the fluid-filled area at the back of the foetus’ neck – called ‘nuchal translucency’ (NT) – and the larger the measurement, the higher the risk that Down’s syndrome is present.

What else can these tests detect?

Women should be aware that these tests may detect abnormalities other than Down’s syndrome. About one in 20 women will have a screening result that indicates a higher chance of an affected pregnancy. Diagnostic testing, including chorionic villus sampling (CVS) or amniocentesis, is then offered to provide a definitive diagnosis.  There is a small risk of miscarriage with these invasive tests.

How accurate are the tests?

1 in 10 babies with downs syndrome will not be identified by screening

You may also be interested in