A simple ultrasound test may be able to rule out the presence of Down syndrome in many fetuses, according to a report published in the medical journal Lancet. Using ultrasound this way could eliminate the need for more-invasive tests that carry a small risk of miscarriage.
The test measures the length of the nasal bone of the fetus during the 12th week of pregnancy, says the author of the report, Kypros Nicolaides, M.D., of King’s College Hospital in London. Babies with Down syndrome generally have relatively flat faces and very small noses, explains Nicolaides. If the nasal bone is visible at 12 weeks, the infant is highly unlikely to have the disorder.
Down syndrome is most common in infants born to older mothers. Amniocentesis is generally recommended for pregnant women over age 35, primarily to check for the disorder. But the test is associated with a miscarriage rate of about 1 percent, Nicolaides notes. If the nasal bone does not appear during ultrasound, amniocentesis is usually recommended, he says, even if the mother is younger than 35.