Nuchal thickness is evaluated in:

Ans. (c) Ante-natal USG second trimester* The nuchal thickness is a parameter that is measured in a second trimester scan (18-22 weeks) and it is not to be mixed with nuchal translucency (which is measured in the first trimester at 11-14 weeks).* The nuchal thickness is measured in a second trimester scan .* Nuchal translucency scan is performed between 11 and 14 weeks of gestation, because the accuracy is best in this period.* The scan is obtained with the fetus in sagittal section and a neutral position of the fetal head* The head of the fetus should neither be hyper-flexed nor extended, either of which can influence the nuchal translucency thickness.* Both are used for diagnosis of Trisomy 21 prenatally.