None can be definitive, thus if screening is positive, either amniocentesis or chorionic villus sampling is required to confirm the diagnosis. Screening in both the first and second trimesters is better than just screening in the first trimester. The different screening techniques in use are able to pick up 90–95% of cases, with a false-positive rate of 2–5%. If Down syndrome occurs in one in 500 pregnancies with a 90% detection rate and the test used has a 5% false-positive rate, this means, of 26 women who test positive on screening, only one will have Down syndrome confirmed. If the screening test has a 2% false-positive rate, this means one of eleven who test positive on screening have a fetus with Down syndrome. Ultrasound
Ultrasound imaging can be used to screen for Down syndrome. Findings that indicate increased chances when seen at 14 to 24 weeks of gestation include a small or no nasal bone, large ventricles, nuchal fold thickness, and an abnormal right subclavian artery, among others. The presence or absence of many markers is more accurate. Increased fetal nuchal translucency (NT) indicates an increased possibility of Down syndrome picking up 75–80% of cases and being falsely positive in 6%. Blood tests
Several blood markers can be measured to predict the chances of Down syndrome during the first or second trimester. Testing in both trimesters is sometimes recommended and test results are often combined with ultrasound results.
Regular screening for health problems common in Down syndrome is recommended throughout the persons life.Down syndrome is one of the most common chromosome abnormalities in humans. It occurs in about 1 in 1,000 babies born each year. In 2015, Down syndrome was present in 5.4 million individuals globally and resulted in 27,000 deaths, down from 43,000 deaths in 1990. It is named after British doctor John Langdon Down, who fully described the syndrome in 1866. Some aspects of the condition were described earlier by French psychiatrist Jean-Étienne Dominique Esquirol in 1838 and French physician Édouard Séguin in 1844. The genetic cause of Down syndrome was discovered in 1959. Signs and symptoms
Those with Down syndrome nearly always have physical and intellectual disabilities. As adults, their mental abilities are typically similar to those of an 8- or 9-year-old. They also typically have poor immune function and generally reach developmental milestones at a later age. They have an increased risk of a number of other health problems, including congenital heart defect, epilepsy, leukemia, thyroid diseases, and mental disorders. Physical
People with Down syndrome may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and relatively large tongue. These airway changes lead to obstructive sleep apnea in around half of those with Down syndrome.