What is the significance of increased nuchal translucency at 14 weeks of gestation?

Nuchal translucency(NT) is a term used to describe a sonolucent area in the nuchal region (back of the neck) of the fetus and is typically observed in the first trimester (10-14weeks). Increased NT refers to NT measurement of greater than 2.5mm. One third of fetus with increased nuchal translucency will have a chromosome abnormality, and 1/2 of these are Down syndrome. Ref: Williams Obstetrics 23rd Edition Chapter 13; Obstetrics, Gynecology & Infeility By R Rajan Page 225-6; Textbook of Obstetrics By D. C Dutta, 6th Edition, Page 107.