NT + Blood test
How is a NT done?
What will a NT tell me?
Nuchal (pronounced 'new-cal') translucency or 'NT' is a relatively new screening test. It uses ultrasound to visualise and measure a fluid filled sac at the back of the unborn baby's neck during early pregnancy. NT can be done as early as 10 weeks + 3 days of pregnancy, but it is more accurate when performed after 11 weeks + 3 days and before 13 weeks + 6 days. After 14 weeks, the
lymph system of the baby develops, making the fluid naturally drain away, meaning the test can no longer be done.
Nuchal translucency is used to estimate if a baby is at increased risk of having a chromosomal abnormality. The main genetic disorder screened for is Down syndrome (also called 'trisomy 21'). People with Down syndrome have an extra chromosome. This can make the person have specific physical features and various levels of intellectual disability and possibly other physical problems. However, many people with Down syndrome lead active and full lives in semi-dependent manner. Other extremely rare genetic disorders that may be detected are Edward's syndrome (trisomy 18) and Patau syndrome (trisomy 13).
NT + Blood test
When a woman is offered a nuchal translucency, she will also be offered a blood test. A nuchal translucency alone is about 75% accurate, but if it is combined with the blood test the accuracy can be increased up to 85%. The blood test measures the level of two proteins in the woman's blood. These are called 'pregnancy associated plasma protein - A' or 'PAPP-A' and 'free-beta human chorionic gonadotropin' or 'free BHCG'.
Women are given the choice to just have the nuchal translucency, or to have the nuchal translucency as well as the blood test. However, the blood test cannot be performed on its own without the nuchal translucency. The blood test is best done before the nuchal translucency, but it is possible to have it done at the same time.