Nomograms of fetal nuchal fold thickness for early detection of Down syndrome.

A prospective study was undertaken in North India to find the normative data on the nuchal fold thickness of randomly selected 150 fetuses between 16-22nd week of gestation. The data revealed that the width of nuchal fold thickness ranged between 2-5 mm. The mean for 16-18, > 18-20, and > 20-22 week's gestation was 2.6 +/- 0.2, 3.8 +/- 0.9, and 4.0 +/- 0.8 mm respectively. In one fetus nuchal fold thickness was 6mm at 18 weeks (> 2SD above the normal value) and thus Down Syndrome was suspected. This was later confirmed by amniocentesis and karyotyping.