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Increased nuchal translucency (NT) is seen in about 5% of fetuses (using an NT measurement cutoff of greater than the 95th %ile). As such, it is a relatively common finding in first trimester screening. Increased NT is associated with an increased risk for fetal chromosomal aneuploidy, death, and major fetal anomalies. The risk for fetal aneuploidy / fetal anomaly / fetal demise increases with the degree of NT measurement. Increased NT will trigger a discussion of additional tests, including an early 2nd trimester ultrasound at 16 weeks and and a discussion of invasive testing (chorionic villus sampling or amniocentesis). In most cases, especially in the absence of other visible anomalies on US and no other flags on prenatal screening, the fetus with mildly increased NT will be born alive and well with no concerns.

Note that percentiles are used for NT, as there is a positive association between the age of the fetus and the NT. Therefore the NT percentiles are specific to a particular gestational age.