Using ultrasonography to determine the presence or absence of a bone in the nose of fetuses aged 11 to 14 weeks could help improve the prenatal diagnosis of Down syndrome, according to researchers at King's College Hospital Medical School, London, and Ohio State University, Columbus.
Physicians diagnose Down syndrome with an invasive test—amniocentesis or chorionic villus sampling—in women considered to be at high risk after screening. In addition to maternal age as a risk factor, current screening methods include maternal blood testing during the second trimester and first-trimester fetal nuchal translucency scanning (which measures the accumulation of fluid at the back of the neck).
Stephenson J. Diagnosing Down Syndrome. JAMA. 2001;286(22):2801. doi:10.1001/jama.286.22.2801-JWM10013-2-1