Increased nuchal traslucency in normal karyotype fetuses.

Nuchal traslucency (NT) measurement between 11 and 14 weeks' gestation is a reliable marker for chromosomal abnormalities, including trisomy 21. However, even if conventional karyotyping is normal, increased NT is a predictive value of adverse pregnancy outcome, because it is associated with several fetal malformations, congenital heart defects, genetic syndromes, intrauterine death and miscarriages; the majority of these structural anomalies are undetectable before birth. The risk is proportional to the nuchal translucency thickness, in fact it statistically increases after measurement reaching 3.5 mm or more. However, when these chromosomally normal fetuses with an enlarged NT survive, even if a detailed ultrasound examination and echocardiography fail to reveal any abnormalities, their uneventful outcome and postnatal developmental delay will be not statistically increased when compared to the general population. These parents should be confidently reassured that the residual chance of structural anomalies and abnormal neurodevelopment may not be higher than in the general population.