ABSTRACT
Down syndrome is the commonest cause of severe mental retardation in children. First trimester screening for nuchal translucency ultrasonographically was performed on 1552 women with singleton pregnancies at 10-14 weeks of gestation. The age of women ranged from 16-43 years. The results showed nine cases with increased thickness of nuchal skin >3 mm with a percentage of [0.58%] of total cases. Seven of these nine cases had abnormal chromosomes by karyotyping [77.78%]. Five cases from the seven cases with abnormal chromosomes had trisomy 21 [Down syndrome] which was [71.4%]. Two women of those who had increased nuchal translucency were euploid. Down syndrome is an age-related disorder. Combination of nuchal translucency ultrasound screening with serum screening is recommended for early diagnosis of Down syndrome in the first trimester of pregnancy