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

TLDR

To examine the significance of fetal nuchal translucency at 10‑14 weeks gestation in predicting abnormal fetal karyotype. A prospective screening study of 827 fetuses at the Harris Birthright Research Centre, using first‑trimester karyotyping to assess the incidence of chromosomal defects. The study found a 3% overall incidence of chromosomal defects, rising to 35% in fetuses with nuchal translucency ≥3 mm versus 1% in those with thinner membranes, indicating that NT ≥ 3 mm is a useful first‑trimester marker.

Abstract

OBJECTIVE--To examine the significance of fetal nuchal translucency at 10-14 weeks9 gestation in the prediction of abnormal fetal karyotype. DESIGN--Prospective screening study. SETTING--The Harris Birthright Research Centre for Fetal Medicine, King9s College Hospital, London. SUBJECTS--827 fetuses undergoing first trimester karyotyping by amniocentesis 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 > or = 3 mm is a useful first trimester marker for fetal chromosomal abnormalities.