Objective: To determine the value of sonographic nuchal translucency measurement for the detection of chromosomal abnormalities in high risk pregnancies. Method: The feasibility of nuchal translucency was tested in a prospective study of 1260 pregnancies at 10- 13 weeks' gestation. Results: The nuchal translucency of 3 mm or greater was identified in 41 fetuses (3.2%), 19 of whom proved subsequently by either amniocentesis or postnatal follow-up have chromosomal abnormalities. The sensitivity of nuchal translucency for chromosomal abnormalities was 82.6% (19 of 23 cases), the positive predictive value of nuchal translucency for chromosomal abnormalities detection was 46.3% (19 of 41 cases). Conclusion: The observed sensitivity, false-positive rate and predictive value suggest that sonographic nuchal translucency should be undertaken at 10 to 13 weeks of gestation.