<P> A nuchal scan or nuchal translucency (NT) scan / procedure is a sonographic prenatal screening scan (ultrasound) to detect cardiovascular abnormalities in a fetus, though altered extracellular matrix composition and limited lymphatic drainage can also be detected . </P> <P> Since chromosomal abnormalities can result in impaired cardiovascular development, a nuchal translucency scan is used as a screening, rather than diagnostic, tool for conditions such as Down syndrome, and non-chromosomal abnormalities, including the genetic Di George syndrome and non-genetic Body - stalk anomaly . </P> <P> The scan is carried out at 11--13 + 6 weeks pregnancy and assesses the quantity of fluid collecting within the nape of the fetal neck . There are two distinct measurements--the nuchal translucency, which is measured earlier in pregnancy at the end of the first trimester, and for which there is a lower threshold for increased diameter, and the nuchal fold, which is measured towards the end of the second trimester . The scan may also help confirm both the accuracy of the pregnancy dates and the fetal viability . As nuchal translucency size increases, the chances of a chromosomal abnormality and mortality increase; 65% of the largest translucencies (> 6.5 mm) are due to chromosomal abnormality, while fatality is 19% at this size . </P> <P> All women, whatever their age, have a small risk of delivering a baby with a physical or cognitive disability . The nuchal scan helps physicians estimate the risk of the fetus having Down syndrome or other abnormalities more accurately than by maternal age alone . </P>

When can the nuchal fold scan be done