The ultrasound examination of randomly sampled 149 pregnant women with normal development of pregnancy provided first pilot study measurements in the range of 11 th - 13 th weeks of gestation in our population. The first norms of nuchal translucency thickness were ascertained for the 11 th , 12 th and 13 th week with calculations of values expressed in medians, its multiples, in averages with 2SD and 95 th and 97 th percentiles for these particular weeks of gestation. The highly statistically significant increase of nuchal translucency thickness was confirmed in the range of the 10 th - 14 th weeks of gestation. The use of uniform criteria for nuchal translucency measurements is pointed out because measurements in other departments were statistically significantly higher especially in weeks 11 and 12. Our data have to be extended for examinations to elaborate norms for weeks 10 to 14, as representative for our population as possible in order to implement early prenatal biochemical and ultrasound screening of genetic risk pregnancies in the 9 th - 14 th week of gestation for prenatal prevention of severe chromosomal and other severe congenital anomalies.

        Key words: nuchal translucency, chromosome aberrations, first trimester screening