Nuchal translucency
Screening for trisomy 21
In euploid fetuses the NT thickness increases with fetal CRL.
In 75-80% of trisomy 21 fetuses the NT thickness is above the 95th centile of the normal range.
In trisomy 21 fetuses there is no relationship between NT thickness and maternal age.
Maternal age can be combined with fetal NT to provide effective first-trimester screening for chromosomal abnormalities.