Nuchal translucency measurement and pregnancy outcome in karyotypically normal fetuses

Objective The aim of the study was to evaluate the use of nuchal translucen cy measurement as a marker of adverse pregnancy outcome in karyotypically n ormal fetuses. Methods During the years 1995-99, nuchal translucency (NT) measurement was routinely offered to all women who had their dating scan in our unit. From the data collected we calculated the 95th and 99th centiles of the NT for a given crown-rump length using regression analysis. The NT measurements wer e analyzed in relation to Pregnancy outcome, especially with regards to mis carriage, intrauterine death and diagnosis of fetal structural abnormalitie s, after excluding chromosomal abnormalities. Results The pregnancy outcome was available in 6650 (89%) of the 7500 pregn ancies. In fetuses with an NT over the 99th centile, 17.8% (relative risk 1 2.2, 95% CI 7.2-20.8) had an adverse pregnancy outcome (miscarriage, intrau terine death, or termination for fetal abnormality) versus 1.5% for those w ith a normal measurement. The incidence of structural abnormalities, especi ally heart defects, was significantly increased in the high-NT groups. Thre e out of 11 fetuses with major cardiac abnormalities had an NT measurement over the 99th centile. The calculated relative risk for major heart defects in fetuses with increased NT was 33.5 (95% CT 9-123). Conclusion In the setting of routine antenatal screening, an increased NT m easurement is a marker of a high-risk pregnancy evert in karyotypically nor mal fetuses. In addition, the increased incidence of structural abnormaliti es makes the close follow-up of these pregnancies imperative and should inc lude specialized fetal echocardiography.