[Increased nuchal translucency with normal karyotype].

Nuchal translucency (NT) measurement in first trimester screening between 11 and 14 weeks' gestation has now been clearly identified as a marker for aneuploidies and in particular for trisomy 21. Even in the absence of aneuploidy increased fetal nuchal translucency has been shown to be a marker for fetal heart malformations and numerous other fetal defects and genetic syndromes when the measure is>or=95th centile which is around 3,5 mm for each gestational age. Fetuses with NT thickness above the 99th centile and normal karyotype have a high risk of adverse prenatal outcome and this increase in risk is exponential as the nuchal translucency measurement increases. However, among children born alive with normal ultrasound at 22 weeks of gestation, there was no significant association between NT thickness and development at 2 years as assessed by clinical examination and ASQ scores, when with a control population. Counselling should emphasize that when the karyotype is normal and no fetal structural malformation was missed prenatally following resolution of nuchal thickening, the prognosis is not impaired at the age of 2.