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

Abstract

To examine the significance of fetal nuchal translucency at 10-14 weeks' gestation in the prediction of abnormal fetal karyotype. Prospective screening study. The Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London. 827 fetuses undergoing first trimester karyotyping by amniocentesis or chorionic villus sampling. Incidence of chromosomal defects. 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. Fetal nuchal translucency > or = 3 mm is a useful first trimester marker for fetal chromosomal abnormalities.