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Nuchal Scan Information Sheet

What is a Nuchal Scan?
Nuchal Screening is a simple non-invasive ultrasound test, performed between 11 weeks and 13 weeks + 6 days.  A measurement is taken of the nuchal skin fold behind the baby’s neck, which is then calculated along with the mother’s age and an optional blood test, to give a risk factor for Down’s Syndrome (Trisomy 21).  The Smaller/thinner the skin fold the better.  During  your scan other anatomy/organs are checked to rule out major abnormalities.

The nuchal scan on its own will detect approximately 80% of babies with chromosomal abnormalities such as Down’s syndrome (Trisomy 21), Patau’s Syndrome (Trisomy 13) and Edward’s Syndrome (Trisomy 18).   It will also show up major structural abnormalities which can be visible at this early stage.  The Nuchal Scan is not a substitute for a normal Fetal Anomoly Scan usually carried out at 20-22 weeks.  The detection rate for chromosomal abnormalities can be improved slightly by measuring hormone levels from a blood test.  The combined or integrated test (Nuchal and Blood) as it is known has a detection rate of approximately 90%.  Many couples are happy with the Nuchal Scan on its own, but if you would like a blood test taken please let us know.  We will package the sample and then you will need to send it by guaranteed next day special delivery to the Fetal Medicine Foundation in London.  They will carry out the analysis (cost - £35) and will send the results back to Glen House and we will then add the hormone results with the nuchal data and generate a complete report for you at that stage.

At your Appointment
When you arrive at Glen House you will have your scan and the Ultrasonographer will be able to give you a verbal report on what she has found.  The full report will be sent out in 5-7 days after it has been verified by Dr Fogarty.

What is my Background Risk?
The results will give you the risk of having a baby with Down’s syndrome.

The backgroundrisk is assessed purely on the mother’s age, eg for a 30 year old the risk is 1 in 626.  That means in every 626 pregnant 30 year olds, one will have a baby with Down’s syndrome.

What Does Adjusted Risk Factor Mean?
The adjusted risk is calculated using the mother’s age, the nuchal thickness and blood tests and is more accurate than using the mother’s age only.

The adjusted risk factor is usually better than the background factor.

Example: If you are 30 years old then your ‘background’ risk of having a baby with Down’s Syndrome is 1 in 626.  Assuming the Nuchal skin thickness is thin at 1.6 mm, then the final ‘adjusted’ risk is reduced to 1 in 2267.      Background risk is 1 in 626 adjusted to 1 in 2267.

Next Step?
Every couple will have their own personal approach to their individual risk factor.  Generally, couples who have ended up with a lower risk factor after the nuchal scan may be content and not want any more tests.  However, if after the nuchal scan your risk factor has increased or you are still not happy, you will be counselled regarding an amniocentesis (see amnio section on Dr Fogarty’s website).  Generally I would not recommend an amnio unless your risk was higher than 1 in 200

Trisomy 21
On your result sheet Down’s syndrome is referred to as Trisomy 21.

Please do not hesitate to ‘phone to speak to the Ultrasonographers if you have any queries about your result, or want to arrange an amniocentesis.

If nuchal translucency is performed a Triple Test is not necessary and will provide no further information.


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