Welcome to HCM.
I presume that you mean to say your wife is 3 months pregnant.
Nuchal Thickness (Nuchal Translucency) of 2.4 Cms. is within normal limits. Up to 3 cms., by 14 Weeks of pregnancy
is within normal limits.
Abnormally thick Nuchal translucency is seen in case of Chromosomal disorders such as Down's Syndrome. Some sonologists also look for Nasal Bone
. Detection of Nasal bone further minimizes the possibility of Chromosomal anomalies.