The Value of First Trimester Nuchal Translucency Measurements in Changing Risks for Down Syndrome.

Publication/Presentation Date



OBJECTIVE: To determine how first-trimester screening of nuchal translucency (NT) affects a priori and ultrasound-adjusted Down syndrome (DS) risks.

STUDY DESIGN: Data were collected from May 1999 through April 2000 for referral of first-trimester NT assessment. Using the Fetal Medicine Foundation First-Trimester Screening Program, adjusted DS risks were calculated utilizing a priori age-related risks, crown-rump length (CRL), and NT. For this analysis, twins were excluded. Odds ratio (OR) with 95% confidence interval (95% CI) was used to compare a priori and ultrasound-adjusted risks by NT.

RESULTS: A total of 544 ultrasounds were performed during the study period. The mean and standard deviation (SD) age of patients screened was 29 (7.0) years old; 155 (28.5%) were 35 and older. The mean (SD) gestational age by last menstrual period was 12.1 (1.3) weeks and by CRL 12.0 (1.6) weeks. Based on a priori risks, 153 (28.1%) had a DS risk greater than 1:300. After ultrasound, 37 (6.8%) had DS risks greater than 1:300 (OR = 0.2, 95% CI = 0.1-0.3). In only those women who had an a priori DS risk greater than 1:300, 140 (84%) reduced their risk to less than 1:300. Also, of the 21 women who had an a priori and ultrasound-adjusted risk greater than 1:300 for DS, 13 (62%) also decreased their risk but not to less than 1:300.

CONCLUSION: There is a significant number of women who have their DS risks adjusted favorably to less than 1:300 by NT screening. Even for those women who are at high risk for DS, the vast majority had their DS risks reduced by NT screening.


Am J Obstet Gynecol 2001;184(S155):Abstract #-526


Obstetrics and Gynecology


Department of Obstetrics and Gynecology, Department of Obstetrics and Gynecology Faculty

Document Type


This document is currently not available here.