Fetal nuchal translucency: Ultrasound screening for chromosomal defects in first trimester of pregnancy

Abstract

Objective - To examine the significance of fetal nuchal translucency at 10-14 weeks' gestation in the prediction of abnormal fetal karyotype. Design - Prospective screening study. Setting - The Harris Birthright Research Center for Fetal Medicine, King's College Hospital, London. Subjects - 827 fetuses undergoing first trimester karyotyping by aminocentesis or chorionic villus sampling. Main outcome measure - Incidence of chromosomal defects. Results - The incidence of chromosomal defects was 3% (28 of 827 cases). In the 51 (6%) fetuses with nuchal translucency 3-8 mm thick the incidence of chromosomal defects was 35% (18 cases). In contrast, only 10 of the remaining 776 (1%) fetuses were chromosomally abnormal. Conclusion - Fetal nuchal translucency ≥ 3 mm is a useful first trimester marker for fetal chromosomal abnormalities.