Background: Objective:The aim of this work was to evaluate accuracy of the ultrasonographic assessment at the first or the second trimester of gestation as a predictor of adverse outcome in high risk pregnancies. Patients and methods:A cross sectional study was conducted on 85 consecutive high risk pregnancies attending the Antenatal Clinic and Medical Genetics Center of Ain Shams University. Nuchal translucency thickness was obtained for all cases recruited during 1^st trimester. Nuchal fold thickness was obtained for all cases recruited during 2^nd trimester.We prospectively evaluated the outcome of each pregnancy. Results:The mean age of participants, mean marriage duration, and gestational age were 32.5 ± 6 years, 7.1±3.3 years and 14.5±2.1weeks respectively.Increased NT thickness and NF thickness were present in5%, and 8.89% respectively.Down syndrome was found in 1.2% of current pregnancy outcome, while, cystic hygroma was found in 1.2%, cystic hygroma with hydrops was found in 1.2%, skeletal dysplasia and renal agenesis was found in1.2% missed abortion was found in 3.53%.There is a highly significant difference between normal outcome pregnancy and abnormal outcome pregnancy regarding mean NF thickness while no significant differences regarding NT thickness. Conclusion:The findings of our prospective study demonstrate the feasibility of using NF thickness to screen for aneuploidies, adverse perinatal outcome in high risk    pregnancies.