Fetal nuchal translucency is a measurement taken during a first trimester pregnancy screening to check for Down syndrome and other developmental abnormalities. This screening may be recommended to women at high risk of carrying fetuses with chromosomal abnormalities, and in some obstetrics practices it is routinely given to all patients. Typically, at the same time fetal nuchal translucency is measured, a blood sample will be taken for additional analysis and the patient will also have a routine prenatal examination.
In this pregnancy screening, the fetus is visualized on an ultrasound machine. The technician or doctor moves the ultrasound transducer into a position allowing for a clear view of the fetus in profile. The crown-to-rump length of the fetus can be measured to conform gestational age, and the person administering the ultrasound can also check for any signs of obvious abnormalities. In addition, the fluid behind the neck of the fetus is measured to obtain a fetal nuchal translucency measurement.
In this test, also known as a nuchal fold test, the doctor is looking for an unusually high level of fluid. Down syndrome and certain other chromosomal abnormalities are linked with increased deposits behind the neck of the fetus. It is important to administer the test between the 11th and 14th weeks of pregnancy, as the buildup of fluid will naturally begin to resolve after this point and can no longer be used to achieve reliable results.
A positive result on a fetal nuchal translucency test does not necessarily mean that a fetus has Down syndrome. False positives can occur, and some babies simply naturally have more fluid at the back of the neck. Additional testing is needed to make a positive diagnosis and the doctor can provide the patient with more information about testing options. When discussing follow up options with the doctor, parents may want to ask about the risks and benefits of various approaches.
Parents have a number of choices if they receive a positive result on a fetal nuchal translucency screening. They can take a wait and see approach, working with the doctor to monitor the fetus for problems as the pregnancy develops. Specific findings during the ultrasound examination can help parents and doctors make a decision about the next step, as there are other physical indicators people can look for to identify Down syndrome, like absence of a nasal bone. Parents can also pursue additional testing to confirm the diagnosis. This testing can help parents make decisions about the pregnancy and will be helpful for people who want to be fully prepared for the baby at birth. Infants with Down syndrome may have additional needs immediately after birth and people with Down syndrome need supportive care and access to appropriate education and other services.