Screening for fetal chromosomal abnormalities with nuchal translucency measurement in the first trimester.

Abstract

Objective:To describe the detection rate of first-trimester chromosomal abnormality screening with nuchal translucency (NT) measurement and maternal age in our population. Methods: We have screened the fetuses between 11 to 14 weeks' gestation according to the Fetal Medicine Foundation's (London) instructions and used the FMF's software to assess the risk based on maternal age, crown-rump length (CRL) and NT. Fetal karyotyping was offered when screening for Down syndrome identified a risk greater than 1 in 300. Sensitivity and false-positive rates were calculated for different cut-offs. Results: Pregnancy outcome was obtained from 4,598 babies of 4,365 mothers. The median maternal age of the 4,365 women was 28.2 +/- 5.3 (range 15-47) years, and the median fetal CRL was 65.4 +/- 9.4 (range 45-81) mm. There was risk estimate of 1 in 300 in 214 fetuses (4.7%). Chromosomal abnormalities were identified in 32 fetuses, including 19 cases of trisomy 21, and 13 cases of other abnormalities. The sensitivity using NT and maternal age in detecting trisomy 21 with a cut-off 1 in 300 was 73.6% (14/19) with a false-positive rate of 4.7%. At a false-positive rate of 3%, with a cut-off level 1 in 210, the detection rate was 73.6%. The detection rate for all chromosomal abnormalities with a cut-off level 1 in 300 was 68.8% (22/32) at a false-positive rate of 4.7%. Conclusion: The first-trimester screening for chromosomal anomalies with NT measurement, when carried out according to the accepted standards of quality, is useful. Copyright (c) 2006 S. Karger AG, Basel.