[Nuchal translucency: technical measurement and value]

Nuchal translucency measurement is a very powerful screening test to detect chromosomal anomalies or other malformations. The technique for measurement is based on strict guidelines that will be described in this paper. Training is mandatory. Risk calculation for chromosomal anomalies (trisomy 21) must also consider maternal age and gestational age. In France, in 1999 the predictive positive value of nuchal translucency for chromosomal anomalies was about 1/7. Other ultrasound markers such as the absence of nasal bone combined with nuchal translucency increase detection. A higher performance will be achieved when ultrasound will be combined with first-trimester maternal serum markers.