However, the scan can help a woman decide whether or not to have a diagnostic test.
The “crown-rump” length will be measured and your expected date of delivery confirmed.
During the scan we will measure the amount of fluid at the back of your baby’s neck (Nuchal Translucency).
Using this measurement, along with the mother’s age, the age of the baby and the presence or absence of the baby’s nasal bone, a risk is calculated to determine the likelihood of your baby having a chromosomal abnormality. If the calculation gives you an increased risk, you may be happy to continue without further investigation or you may feel you want a more definite answer.
The nuchal is measured using ultrasound when the foetus is between 11 weeks and 13 weeks plus six days gestation.
All foetuses will have some fluid; those with Down’s syndrome have an increased amount.