Nuchal Translucency Screening - 11-13 weeks gestation

The vast majority of babies are normal. However all women, regardless of their age, have a small risk of delivering a baby with a physical and/or mental handicap. In some cases the handicap is due to a chromosomal abnormality such as Down’s Syndrome.

The only way to know for certain whether or not the fetus has a chromosomal abnormality is by having one of the invasive tests – chorion villus sampling (CVS) or amniocentesis (amnio). These tests carry a risk of miscarriage of about 1%.

As a guide, an invasive test is usually offered if the risk of Downs Syndrome is 1:300 or higher. The most accurate way of estimating the risk is by nuchal translucency screening which is carried out at 11 – 13 weeks gestation. The result depends upon the following factors:

• The stage of the pregnancy
• The age of the mother
• The amount of fluid behind the neck of the fetus (nuchal translucency)
• The presence or absence of the fetal nasal bone
• The presence or absence of any physical abnormalities
• The level of two hormones in the mothers blood (b-hCG & PAPP-A)

It is up to you and your partner to decide whether or not the risk of the fetus having a chromosomal abnormality is high enough to warrant having an invasive test.

After the test, the results will be discussed with you and if you are happy with your result you can carry on normally with your pregnancy. This is the outcome in the vast majority of cases.

If you decide that you wish to have an invasive test, then the procedure will be arranged at your nearest referral centre in the case of CVS, or at your local hospital in the case of amniocentesis.

We will make the necessary arrangements for you and speak to our colleagues in the NHS to ensure a smooth transition back into the care of your own clinical team.