The Parameter measured in the USG, measures 3.7 mm. It is:

Nuchal translucency (NT) is the sonographic appearance of a collection of fluid under the skin behind the fetal neck in the first-trimester of pregnancy. In fetuses with chromosomal abnormalities, cardiac defects and many genetic syndromes -NT thickness is increased. Up to 3 mm is considered normal. More than 3 mm NT is one of the markers of Down syndrome on USG.