The nuchal scan is the standard first-trimester screening scan in the UK. It measures a small pocket of fluid behind your baby’s neck, called the nuchal translucency, and combines that with a blood test and your age to estimate the risk of certain chromosomal conditions, including Down’s syndrome. It also gives a much closer look at your baby’s developing anatomy than was possible at viability scans.
When does the nuchal scan happen?
The nuchal scan is performed at 11-13 weeks of pregnancy. The window is precise: the nuchal translucency measurement is only valid between 11 weeks and 13 weeks 6 days, so timing matters.
What is the nuchal scan for?
The purpose of a nuchal scan is to:
- Measure the volume of translucent fluid in the space behind your baby’s neck
- Estimate your baby’s risk of having chromosomal abnormalities such as Down’s syndrome, Edwards syndrome, Patau syndrome, and Turner syndrome
- Determine whether more invasive diagnostic testing, such as CVS (chorionic villus sampling) or amniocentesis, is necessary
- Examine your baby’s heart in greater detail
A routine blood test is also taken during the nuchal scan. The combination of the scan measurement and the blood test gives a more accurate risk estimate than either on its own.
What the result actually means
The nuchal scan is a screening test, not a diagnostic test. It produces a probability, such as a 1 in 5,000 chance, not a yes/no answer. Most parents are reassured by a low-risk result. Where the result is higher-risk, the next step is usually a non-invasive prenatal test (NIPT) or, less commonly, diagnostic testing such as CVS or amniocentesis to give a definitive answer. Dr Duncan will discuss your options with you in detail at the appointment if needed.
Dr Duncan offers NIPT directly, with results usually available within 48 hours. NIPT costs £500. Where invasive diagnostic testing is appropriate, Dr Duncan also performs CVS and amniocentesis.
What happens during my appointment?
The scan is painless as ultrasound uses sound waves only, with no radiation, so is safe for both you and your baby.
You will lie comfortably on the examination couch, and a small amount of water-based gel is applied to your abdomen so the probe can move smoothly across the skin. You will see the live images on the screen as the scan progresses, and Dr Duncan talks through what he is looking at as he goes. The bloods are drawn at the same appointment.
What happens if the result is higher-risk?
If the combined result is higher-risk, Dr Duncan will discuss the options with you fully at the same appointment, including NIPT and, where appropriate, diagnostic options like CVS or amniocentesis. Dr Duncan is a sub-specialist in maternal and fetal medicine, and most early-pregnancy findings can be assessed and explained on the spot, with any further investigations arranged from there.
Booking your nuchal scan
To book a nuchal scan, please contact the practice or book online. Because of the strict 11-13 week window, please book early in your pregnancy to secure a slot at the right gestation.
For a fuller picture of all the scans available through pregnancy, see Ultrasound Baby Scans.
