Thickened nuchal skin fold Thickened skin folds of neck The measurement of nuchal fold (NF) thickness during the second trimester is considered to be one of the most sensitive and specific isolated ultrasound marker for the identification of suspected cases of trisomy 21. Thick NF may also be seen in other aneuploidies as well as Turner's syndrome, Noonan's syndrome, Roberts syndrome, Zellweger syndrome and with congenital heart disease and with pathogenic CNVs. A thickened nuchal fold should be distinguished from cystic hygroma, in which the skin in this area has fluid-filled loculations. A thickened nuchal fold should not be confused with nuchal translucency, which is a specific measurement of fluid in the posterior aspect of the neck at 11 to 14 weeks gestation (see practice guidelines at http://www.sogc.org). Increased nuchal fold Thick nuchal fold HP:0000474 Excess nuchal skin HP:0000477 Thickened nuchal skin A thickening of the skin thickness in the posterior aspect of the fetal neck. A nuchal fold (NF) measurement is obtained in a transverse section of the fetal head at the level of the cavum septum pellucidum and thalami, angled posteriorly to include the cerebellum. The measurement is taken from the outer edge of the occiput bone to the outer skin limit directly in the midline. An NF measurement greater than 5 mm at 14 to 17+6 weeks of gestation, or 6 mm at 18 to 28 weeks has been associated with a markedly increased risk for Down syndrome. Thickened skin over the neck Increased nuchal fold thickness UMLS:C1836940 Fetal ultrasound soft marker Fetal neck anomaly