ABSTRACT
Nuchal translucency (NT) is the single most important marker for chromosomal abnormalities in the first trimester and by far the most widely researched. Screening for trisomy 21 by combining NT with maternal age and maternal serum biochemistry results in a detection rate of about 80% of cases for a 3% invasive testing rate. The NT is increased in other chromosomal abnormalities, and a screening program for trisomy 21 will also detect the majority of fetuses with other trisomies. Heart abnormalities are associated with increased NT thickness in chromosomally normal fetuses. Increased fetal NT is associated with a high prevalence of major fetal abnormalities. A careful anatomical survey should therefore be performed in chromosomally normal fetuses with increased NT. Increased NT has been associated with a large number of genetic syndromes.
