Nuchal Translucency (NT)

Definition - What does Nuchal Translucency (NT) mean?

Nuchal translucency is a small, thin, fluid-filled area of transparency behind the neck of the developing fetus. Early in pregnancy, between the 10th and 14th week, this area is measured in a nuchal translucency scan.

This measurement is used as a screening tool in order to detect various chromosomal and genetic abnormalities such as Down’s syndrome, where approximate 75% of fetuses have increased nuchal translucency.

FertilitySmarts explains Nuchal Translucency (NT)

In the developing fetus, between the 10th and 14th week of gestation, a small area between the skin and neck tissue gets filled with fluid which can be seen in an ultrasound image. The amount of fluid filled space is known as the nuchal translucency and the measurement of this area’s borders can be used to screen the developing fetus for various abnormalities.

Optimally, during the 11th week, an ultrasound is used to measure the width of the area from the top layer to the bottom layer and this, in combination with other sonogram findings, including the absence of fetal nasal bone or an indication of short legs, can accurately specify the abnormality. In cases of increased nuchal translucency, there may be conditions such as:

  • Turner Syndrome (45, X)
  • Down’s syndrome (Trisomy 21)

Fetuses with increased nuchal translucency but with normal genetic chromosomes are still at high risk for other disabilities such as:

  • Heart Disease: septal defects
  • Malformation of the intestine: Atresia or stenosis
  • Developmental delay
  • Fetal death

Due to the fact that nuchal translucency measures may vary depending on the skills of the sonographer, results are used in screening, but never solely to diagnose. After a fetus is diagnosed as having increased nuchal translucency, other diagnostic evaluations such as maternal and fetal genetic testing is offered.

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