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Nuchal translucency scan
The nuchal translucency scan is the first-trimester ultrasound performed between 11 and 14 weeks. It measures the amount of fluid at the back of the baby's neck and gives information about chromosomal abnormalities and the baby's anatomy.
When it is done
The scan is performed between 11 and 14 weeks of pregnancy. At the same time we date the pregnancy accurately, which is especially useful when the exact date of the last period is not known.
What the scan shows
Nuchal translucency is the amount of fluid that collects at the back of the baby's neck. Measuring it gives valuable information about chromosomal abnormalities, particularly Down syndrome, and about possible congenital heart defects in the baby.
In the same scan we also check the baby's anatomy. We look for the nasal bone, the stomach and the bladder, and at the formation of the arms, legs and skull. In this way a number of structural abnormalities, such as anencephaly and omphalocele, can be detected.
The blood test that goes with it
Alongside the scan, a blood sample is taken from the mother and two substances are measured: PAPP-A and free beta-hCG. Combining the nuchal translucency measurement with these two values raises the reliability of the assessment, from about 85% to about 90%.
Doppler of the uterine arteries
During the same scan we use the Doppler technique to check blood flow in the mother's uterine arteries. From this we judge whether the placenta has developed properly, that is, whether the circulation between the baby and the placenta is working as it should.
Frequently asked questions
Does the nuchal translucency scan tell me for certain whether the baby has a syndrome?
No. Chromosomal abnormalities are detected indirectly, through markers such as nuchal translucency, and the scan gives a risk estimate, not a diagnosis. A definite answer comes only from an invasive test, such as chorionic villus sampling or amniocentesis. We will explain the result and what it means for you on the same day.
What happens if the measurement is raised?
A raised nuchal translucency is a positive marker and means that further investigation is needed. Between 11 and 14 weeks chorionic villus sampling (CVS) can be done, with the result in about 3 days, or after the 15th week amniocentesis. Because nuchal translucency is also linked to heart defects, a scan of the baby's heart is recommended between 22 and 24 weeks. Every next step is decided together with you.
Is any preparation needed?
No. The scan does not require you to drink fluids beforehand. The blood sample for PAPP-A and free beta-hCG is taken on the same day. You only need to come on the date we set, within the 11–14 week window.
I cannot remember my last period. Can the pregnancy still be dated?
Yes. The nuchal translucency scan dates the pregnancy accurately, precisely for cases where the date of the last period is not known. Mention it at your first visit so that we can schedule the scan correctly.