ABSTRACT
Increased fetal nuchal translucency (NT) seems to be a well established ultrasonographic marker for aneuploidy screening, particularly when it is measured during the first trimester1-5. To date, NT screening combined with maternal age at early mid-trimester has been able to identify about 75-80% of chromosomal abnormalities with a falsepositive rate of 5%1,6-12. Recently, enlarged fetal NT has been associated with structural abnormalities, rare genetic syndromes and adverse perinatal outcome in chromosomally normal fetuses13-24. The pathophysiological mechanism of an increased NT is not well known, but a temporary cardiac dysfunction at early gestation has been suggested25,26. Changes in ductus venosus (DV) blood flow velocities in the first and early second trimester have been reported in some chromosomally abnormal fetuses with enlarged NT27-31. Moreover, an abnormal DV flow velocity waveform has been associated with adverse perinatal outcome in fetuses with normal chromosomes24,32,33.
