The aim of this study was to examine the relationship between nuchal translucency measurements and outcome of pregnancy with special regard to fetuses with an enlarged nuchal translucency and a normal karyotype. Fetal nuchal translucency measurements were performed on consecutive mothers attending the prenatal diagnosis center of our hospital. A complete follow-up was obtained in 88.4% of the cases. Of the 74 fetuses (4.4%) with an enlarged nuchal translucency (> or = 3 mm), 25 (33.8%) had an abnormal karyotype. Two pregnancies ended in a spontaneous abortion before karyotyping was performed. In the remaining 47 eukaryotic fetuses with enlarged nuchal translucency, five (10.6%) had a structural anomaly, two were affected by genetic syndromes (4.2%) and an additional four fetuses (8.5%) were affected by a single-gene disorder. A spontaneous abortion or an intrauterine death occurred in 6.4% and in 2.1% of these fetuses, respectively. The total incidence of an unfavorable outcome in the group of chromosomally normal fetuses with enlarged nuchal translucency was 32%. In contrast, in the group with a normal nuchal translucency (< 3 mm), the incidence of an unfavorable outcome was 7.5%. There is a strong association between enlarged nuchal translucency measurements and congenital (structural and genetic) abnormalities, as assessed by receiver operator characteristic analysis. This may represent, in fetuses with a normal karyotype, a non-specific sign of a disturbance in the developmental process. In these cases, detailed ultrasound surveillance is recommended.