Down syndrome, also known as trisomy 21, is a chromosomal disorder occurring in roughly one in every 800 live births. The condition produces varying degrees of mental retardation and a range of physical deformities, including a small nose and thick neck, which are detectable more or less in early pregnancy. Detecting Down syndrome early in pregnancy could be as plain as the nose on the baby's face.
British scientists say failure to detect a nose bone on ultrasound tests performed at 11 to 14 weeks of gestation is an almost sure sign that the fetus suffers from Down syndrome, a grave genetic disease that prompts many parents to terminate pregnancies. Combined with other important risk factors for the disorder, such as a mother's advancing age, the test is even more accurate at catching affected fetuses.
Dr. Kypros Nicolaides, a fetal medicine specialist at King's College, in London, says no other tests available to doctors approach the face picture's ability to detect Down syndrome. "The bone is white, whereas absence of bone produces a blackness," Nicolaides says. "In a place where you should be seeing a whiteness you are seeing a blackness."
The combination of nasal bone screening with several other Down syndrome tests can identify the disorder in more than 98 percent of babies.