What is the "first look" (Nuchal folds) test my doctor suggested? How can the doctor see Down syndrome on an ultrasound? What does the blood test reveal?
The "first look" or Nuchal folds test, also know as the Nuchal translucency test (NT), is recommended in the first trimester as a tool to screen for your risk of having a baby with Down syndrome. In the past, women over 35, who are considered to have the greatest risk of having a Down syndrome baby, were offered the option of being tested by using chorionic villus sampling (CVS) or amniocentesis. The latest recommendation by ACOG (American College of Obstetricians and Gynecologists) is that all women be offered the option to be screened using the Nuchal folds test and a blood test.
The Nuchal folds test is a screening test done by using ultrasound between week 11 and 14 of your pregnancy. (The ultrasound technicians that do this test must have special training. The Fetal Medicine Foundation based in London, England, provides certification to qualified screeners.)
During the test, a technician will look at the folds at the back of the unborn baby's neck to measure its thickness. Researchers have measured these folds and know what the average thickness should be according to the fetus's gestational age. (Babies with Down syndrome tend to have increased fluid accumulation here). This is a screening test that tells the likelihood of a baby being born with Down syndrome. If the test results are positive, further diagnostic testing in the second trimester will be recommended, such as an amniocentesis and CVS.
There is a blood test that many hospitals and doctors do in conjunction with the NT test. Having the results of this test in combination with the results of the NT test will help your doctor determine the likelihood of your baby having a chromosomal abnormality. This test measure two proteins in the blood: free Beta-hcg (a component of human chorionic gonadotropin) and PAPPA (pregnancy-associated plasma protein-A).
The NT test has a low false-positive rate. If the test results are negative, it means that it is very unlikely that your baby will have this chromosomal abnormality. If the results are positive, you will talk with your doctor and most likely a genetics counselor to look at your age, the baby's age, family history, and so on. This will give you a chance to ask questions and decide on second trimester tests.
At times, all this testing can seem overwhelming, but it helps you and your doctor make important decisions in regards to the health of you and your baby. If you don't understand the results or have questions, don't be afraid to ask more questions until you do.