The Value of First Trimester Nuchal Translucency Measurements in Changing Risks for Down Syndrome.
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.
Published In/Presented At
Fisher, A. J., Guzman, E. R., Smulian, J. C., Waldron, R. Vintzileos, A. M. (2000, February). The Value of First Trimester Nuchal Translucency Measurements in Changing Risks for Down Syndrome. Poster Presented at: The 21st Annual Meeting of the Society for Maternal-Fetal Medicine. Reno, Nevada.
Obstetrics and Gynecology
Department of Obstetrics and Gynecology, Department of Obstetrics and Gynecology Faculty