Although a newborn's physical characteristics may lead doctors to suspect Down syndrome, a genetic test called a karyotype must be done to confirm the diagnosis. A karyotype involves testing a small amount of the baby's blood.
It is also possible to screen for and diagnose Down syndrome during pregnancy. A screening test estimates a woman's risk of having a child with Down syndrome. A diagnostic test determines whether the fetus has Down syndrome.
Two blood tests, the triple screen and the alpha-fetoprotein, are the most common prenatal screening tests and are often done in combination with a detailed sonogram (ultrasound). These tests are usually offered to a pregnant woman between week 15 and week 20 of pregnancy. However, these tests also have a high number of false positives, or results that indicate Down syndrome when the condition is not really present. Any time the test comes back positive, further testing must be done to confirm the diagnosis. Also, some women may receive false-negative results; in other words, the test may fail to detect Down syndrome when it does exist.
The prenatal tests used to diagnose Down syndrome are chorionic villus sampling (CVS), amniocentesis, and percutaneous umbilical blood sampling (PUBS). These tests do carry a small risk of miscarriage, because they require insertion of a needle into the placenta or umbilical cord to examine the baby's chromosomes. These tests accurately diagnose Down syndrome 98% to 99% of the time. CVS is typically performed between eight and 12 weeks of pregnancy; amniocentesis is performed between 12 and 20 weeks; and PUBS can be done after 20 weeks. There are tests being developed that only require a sample of the mother's blood in order to test for certain fetal and maternal DNA fragments. These tests may prove to be more accurate, and less risky, than the tests being used now.
What Are the Treatments for Down Syndrome?
Although there is no cure for Down syndrome, children born with the condition can lead productive lives. Everyone born with Down syndrome exhibits some level of cognitive impairment, but this usually falls within the mild to moderate range. Just like other children, babies with Down syndrome will learn basic skills -- such as sitting, walking, talking, and self-care (such as toilet training and bathing) -- but they will do so at a delayed pace. Early intervention programs, including physical therapy, begun shortly after birth, can help strengthen muscles for these basic motor skills.