<prompt> Fetal nuchal skin thickness is useful in detecting:Fetal infectionDown syndromeAnencephalyHydrops fetalis  <response>: Nuchal thickness should be less than 3 mm in 12 to 13 weeks It should be 6 mm after 14 weeks and it is called as nuchal fold Nuchal thicknessfold 6 mm after 14 weeks is suggestive of downs syndrome 