The nuchal translucency is an exam that is used to measure the amount of fluid in the region of the neck of the fetus, performed during ultrasound, performed between the 11th and 14th weeks of gestation. This test is used to calculate the risk of the baby having a malformation or syndrome, such as Down syndrome.
When malformations or genetic diseases are present, the fetus tends to accumulate fluid in the neck region, so if the nuchal translucency measurement is increased, above 2.5 mm, it means that there may be some change in its development.
Thus, the measurement of the altered nuchal translucency does not confirm that the baby has a genetic disease or malformation, indicating only the increased risk of these alterations and, in this case, the obstetrician will request other tests such as amniocentesis, for example, to confirm or not the diagnosis.
The exam price varies between 110 to 400 reais, depending on the clinic where it is performed, but, if requested by the obstetrician, in prenatal consultations, it can be done by SUS without being charged.
How it is done and reference values
The nuchal translucency is done during one of the prenatal ultrasounds and, at this moment, the doctor measures the size and the amount of liquid that is in the region behind the baby's neck, without the need for any other special procedure.
The nuchal translucency values can be:
- Normal: less than 2.5 mm Altered: equal to or greater than 2.5 mm
An examination with increased value does not guarantee that the baby suffers from any alteration, but indicates that there is a greater risk and, therefore, the obstetrician will request other tests, such as amniocentesis, which collects samples of the amniotic fluid, or cordocentesis, which evaluates a blood sample from the umbilical cord. Learn more about how amniocentesis or cordocentesis are made.
If during the ultrasonography there is also the absence of the nasal bone, the risk of some malformation increases more, as the nasal bone is usually absent in cases of syndromes.
In addition to nuchal translucency, the mother's age and family history of chromosomal changes or genetic diseases are also important in calculating the baby's risk of having one of these changes.
When to do nuchal translucency
This exam should be done between the 11th to the 14th week of gestation, as it is when the fetus is between 45 and 84 mm in length and it is possible to calculate the nuchal translucency measurement.
It can also be known with morphological ultrasound of the first trimester, because, in addition to the measurement of the baby's neck, it also helps to identify malformations in the bones, heart and blood vessels.
Learn about the other tests that are needed in the first trimester of pregnancy.
