What is nuchal translucency?
This is a collection of fluid under the skin at the back of a baby's neck at 10-14 weeks that can be measured using ultrasound. All babies have some fluid, but in many babies with Down's syndrome, the nuchal translucency (NT) is increased.
An NT scan is a method of assessing whether your baby is likely to have Down's syndrome. It's a screening test. A screening test can only estimate the risk of your baby having Down's, as opposed to a diagnostic test, such as CVS or amniocentesis, which will give you a definite diagnosis (but also carries a small risk of miscarriage).
The NT scan can't tell for certain whether your baby is affected. However, it can help you decide whether or not to have a diagnostic test.
When can I have the test?
NT scans are usually performed from 11 to 13 weeks + 6 days of pregnancy. Before 11 weeks the scan is technically difficult because the baby is so tiny and, after 14 weeks, excess fluid may be absorbed by the baby's developing lymphatic system.
What is a normal measurement?
An NT measurement of up to 2.0mm is normal at about 11 weeks, and up to about 2.8mm by 13 weeks and 6 days. This is because the NT normally grows in proportion to the growth of the baby. A baby with a normal NT of 1.3mm will be low risk.
If the NT is increased, it does not mean there is definitely a problem. Some normal babies have increased fluid, too. A baby with an NT of 2.9mm, which is at the upper limit of the normal range, will have a higher risk, but
nine out of 10 babies with a measurement between 2.5mm and 3.5mm will be completely normal.
As the NT increases, so does the risk. A baby with an NT of 6mm and will be very high risk for Down's, as well as other chromosomal and genetic syndromes and heart problems. Fortunately, not many babies have as much fluid as this.
Abnormal Nuchal Translucency Scan
,
Reply With Quote
Bookmarks