1. Ultrasound imaging

2. Learning Outcomes Suggested learning activity
A ‘dating scan’ at 8-14 weeks to determines the stage of pregnancy and the due date
An anomaly scan at weeks may detect serious physical problems
Dating scans are used with tests for marker chemicals which vary normally during pregnancy
Measuring a substance at the wrong time could lead to a false positive result
Suggested learning activity
View ultrasound images at different stages of pregnancy.
View specialised ultrasound images - ‘marker’ nuchal translucency by ultrasound

3. High frequency sounds
An ultrasound scanner picks up high frequency sounds that have bounced off the foetus A ‘dating scan’ is performed at 8-14 weeks to determine the stage of pregnancy and to calculate the due date Dating scans are used in conjunction with biochemical tests for marker chemicals which vary normally during pregnancy

4. 9 week foetus

5. 20 weeks

6. scan showing features

7. 20 week anomaly scan

8. Chemical markers
It is worthwhile noting that measuring a substance at the wrong time could lead to a false positive result For example, at one stage in pregnancy the presence of a high level of a certain chemical marker may indicate that the foetus has a genetic disorder At another stage in pregnancy the same high level would have no significance Another scan is carried out at weeks and this produces an ‘anomaly scan’ At this scan, checks for physical abnormalities can be made

9. Nuchal Translucency Scan (NT)
A NT scan helps experts to estimate, more accurately, the risk of a Down’s syndrome baby The test is carried out at weeks (most reliable results at this time) It allows an assessment to be made of the thickness of fluid at the nape of the neck of the foetus If the Nuchal Translucency exceeds a normal value then there is a risk of chromosomal abnormality (this is not a diagnostic, definite, test)

10. fluid exceeds ‘normal’ value

12. 1. What is a dating scan and when is it done?
2. When is an anomaly scan done and what may it detect?
3. Which type of scan helps to estimate the risk of Down’s syndrome?
4. When is the NT scan carried out and what does it assess?
5. Is this a diagnostic test?

13. 1. What is a dating scan and when is it done?
A ‘dating scan’ at 8-14 weeks is carried out to determine the stage of pregnancy and the due date
2. When is an anomaly scan done and what may it detect?
An anomaly scan at weeks may detect serious physical problems
3. Which type of scan helps to estimate the risk of Down’s syndrome?
A Nuchal Translucency scan helps experts to estimate, more accurately, the risk of a Down’s syndrome baby

14. 4. When is the NT scan carried out and what does it assess?
The test is carried out at weeks as this gives the most reliable results at this time
It allows an assessment to be made of the thickness of fluid at the nape of the neck of the foetus
5. Is this a diagnostic test? No