Nuchal Scan
11 weeks - 14 weeks
This scan is carried out between 11 and 14 weeks. It is usually done through the tummy but occasionally may be carried out through the vagina. The aim of this scan is to:
- Assess the risks of genetic abnormalities such as Down's Syndrome.
- Diagnose major fetal abnormalities (this is done again at 20 weeks with the Anomaly Scan).
- Determine the number of babies you are carrying.
- Date the pregnancy accurately, especially if you cannot recall the date of your last period.
During the scan, the doctor or sonographer will measure the following in order to determine your baby's risk of genetic abnormalities:
- Amount of fluid behind the neck of the fetus (also called the "nuchal fold" or "nuchal translucency")
- The fetal nasal bone (which is often absent or smaller in babies with Down's syndrome)
- Fetal heart rate
- Fetal blood-flow in certain areas of the heart and liver
- Level of two hormones in the mother's blood (free ß-hCG and PAPP-A)
- Any fetal abnormalities
The results of these measurements and tests together will produce a percentage risk of genetic abnormalities. For example, you may be told there is a 1 in 500 chance your baby will have Down's syndrome. The only way to know for sure is to take a sample of the amniotic fluid (called an "Amniocentesis") or the placenta (called "Chorionic Villus Sampling"). Both an amniocentesis and chorionic villus sampling are invasive and slightly increase the risk of miscarriage.
When your results are available, your clinician will discuss them with you. You can then decide whether to have an invasive test to check for genetic abnormalities.
The scan and test will take approximately 30 minutes..
