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Nuchal Translucency Screening (Down's Syndrome Screening)

Nuchal Translucency Screening is a scan and blood test which assesses your baby and gives you the risk of your baby having Down’s Syndrome (Trisomy 21) and is available at both our clinics in Stockport, Manchester and St. Asaph North Wales.

This is a procedure which gives you a risk assessment based on your age, the thickness of the Nuchal Fold at the back of your baby’s neck, the presence or absence of a nasal bone, blood flow in your baby’s heart and a blood test. You will be told your risk of having an affected baby, not whether your baby is definitely affected. This scan can only be performed between 11 weeks 0 days and 13 weeks + 6 days of gestation.

This procedure is non-invasive and therefore presents no risk to your baby.  The main benefit is that because it is done in early pregnancy you can use the information to make an informed choice as to whether or not you should consider invasive testing such as amniocentesis.  Invasive testing carries a small risk of miscarriage.    

We are an accredited site of the Fetal Medicine Foundation (FMF). Our Sonographers are trained and continually assessed by the FMF and we use the FMF software to calculate your risk. Visit the Fetal Medicine Foundation Web site for more information.

There are many tests you can have during your pregnancy to check that your baby is healthy. Some tests give you a risk assessment of the likelihood of having a baby with an abnormality and some give you a definite answer. The tests giving a definite answer are invasive tests and carry a risk of miscarriage. Studies have been undertaken to see which tests are the most accurate without the risk of miscarriage and these tests are listed below.

Many women want to know as soon as possible into their pregnancy if their baby is normal. The vast majority of babies are healthy, but all women, whatever their age have a small risk of their baby being born with an abnormality, some of which are more serious than others. In some cases the problem is due to a chromosomal abnormality such as Down’s Syndrome, when the baby receives an extra chromosome 21 (Trisomy 21). It is more common with older mothers, but can occur whatever the age of the mother. See the Risk Table.

By April 2007, all pregnant women in the UK should be offered screening tests for Down’s Syndrome with a false positive rate of less than 3 in 100 and a detection rate of more than of at least 75 out of 100. The tests that meet this standard are:

From 11 to 14 weeks (the first trimester):
Nuchal Translucency (an ultrasound scan)
Combined test (an ultrasound scan and blood test)

From 14 to 20 weeks (the second trimester):
Triple test (a blood test)
Quadruple test ( a blood test)

From 11 to 14 weeks and 14 to 20 weeks:
Integrated test (an ultrasound scan and blood test)
Serum integrated test (a blood test)

It is important to remember that these tests do not give a definite answer, they assess the risks and for all screening tests there is a false positive rate. This is the number of fetuses that the tests say have a condition but are actually found to be normal. That is an unaffected pregnancy with a positive test result.

Different Studies cite different detection and false positive rates. The Fetal Medicine Foundation (FMF) have undertaken the largest studies in Nuchal Translucency screening in order to give as accurate as possible detection and false positive rates. The FMF studies used only staff trained specifically to undertake the Nuchal scan.

Different antenatal departments will also use different odds to determine a "high risk" pregnancy. It is accepted that a risk factor of 1 in 250 is a high risk pregnancy and the mother is likely to be offered further (invasive) test following counseling from her midwife and/or obstetrician.