Nuchal thickness screening is used as an alternative to biochemical screening for Down Syndrome. The same principles apply.

Nuchal thickness screening is carried out by a 10 minute ultrasound examination of the baby between 11 and 14 weeks of pregnancy. The amount of fluid behind the baby's neck is measured in millimeters and a computer used to take this, your age and the baby's size and heart rate into account. The computer programme will tell you what your risks are of having a chromosomally abnormal baby. The risks will be expressed in the form 1 in so many pregnancies. The Consultant will explain the result to you.

The sensitivity of the test is about 85%. That means that if the baby has got Down Syndrome there is an 85% chance that the test will show you to have a risk of 1 in 300 or worse (and further testing advised). If the baby is normal there is still a 5% chance that the computer will produce a high risk figure for your pregnancy. The equivalent figures for most biochemical screening are 55-60% and 5%.

Patient information leaflet:

Nuchal thickness screening can tell you how likely you are to have a baby with Down Syndrome. Nuchal thickness screening can not diagnose Down Syndrome. Invasive testing (amniocentesis or CVS) is needed to be 100% certain that a baby has or hasn't got Down Syndrome. In nuchal thickness screening the family history, mother's age and appearance of the baby are taken into account.

Family history: if you have an aunt, uncle, brother or sister with Down Syndrome or if you have a child with Down Syndrome, it might make your chances bigger of having a baby with Down Syndrome

Mother's age: older mothers are more likely to have babies with Down Syndrome than younger mothers.

The baby’s appearance: all babies have some fluid at the back of their neck. The more fluid there is the more likely the baby has Down Syndrome.

The test

• the Specialist will ask you some questions;

• your baby will be scanned for a few minutes;

• the chance of the baby having Down Syndrome will be worked out;

• the results will be printed on a piece of paper for you to take away;

• the Specialist will explain things to you and arrange further tests if they are needed;

• you will be able to ask questions.

To arrange a test, or consultation, please contact the hospital. Thank you.