Nuchal Translucency Screening (NTS)
Typically done between 11 and 14 weeks of pregnancy, this new type of screening uses an ultrasound and blood test to calculate the risk of some birth defections. Doctors use the ultrasound exam to check the thickness of the back of the fetus’ neck. Your blood is tested for levels of a protein called pregnancy-associated plasma protein and a hormone called human chorionic gonadotropin (hCG). The information from these tests is used to determine if the fetus has a normal or greater than normal chance of having some birth defects.
In an important recent study, NTS found 87% of cases of Down Syndrome when done at 11 weeks of pregnancy. When NTS was followed by another blood test done in the second trimester (maternal serum screening test), 95% of fetuses with Down Syndrome were identified.
With all screening tests, the results are sometimes misleading. In 5% of women who have NTS, results show that their babies have a high risk of having a birth defect when they are actually healthy. This is called a false positive. To find out for sure if the fetus has a birth defect, NTS must be followed by a diagnostic test like chorionic villus sampling or amniocentesis.
NTS is not yet widely used. If you are interested in NTS, talk to your doctor. If she is unable to do the test, she can refer you to someone who can. You should also call your insurance company to find out if they cover the cost of this procedure. NTS allows women to find out early if there are potential health problems with the fetus. This may help them decide whether to have follow-up tests.