Nuchal translucency screening (NT screening) is an ultrasound test done between 11-14 weeks of pregnancy. It is a test that screens for disorders that are caused by extra copies of chromosomes (trisomy 21, trisomy 13, and trisomy 18) as well as other congenital heart defects. The screening measures the base of a fetus’ neck where more fluid is typically at the base of fetuses with extra chromosomes. This spot is known as the nuchal fold and can make the neck appear larger in an ultrasound.
The timing of the nuchal translucency screening is crucial because the nuchal fold becomes less transparent as the baby grows. The base of the neck is only transparent for a short amount of time, and that is why your doctor will order the nuchal translucency screen to be done during weeks 11-14. NT measurements are not conclusive and are not used to tell whether a baby has extra chromosomes or other heart defects. However, the results of the NT screening can be combined with other data to provide doctors with a statistic about the likelihood of a chromosomal disorder.
Unlike other more invasive genetic tests, there are no increased risks associated with nuchal translucency screening. The biggest side effect from the NT screening is the anxiety that can be provoked. False positives are common, as are false negatives. Nuchal translucency screening is not a required screening and can be waived by a mother. For many women, if they are healthy and are not considered to be “high risk” they forgo the NT screening. However, if such chromosomal disorders are present in a family’s genetics or if a pregnancy is considered to be high risk, most women choose to have the screening done. Your doctor can help you determine if nuchal translucency screening is right for you and your baby.
Posted on behalf of Carlos Alarcon, M.D., Marietta OB-GYN Affiliates, P.A.