Do You Know What Causes Down Syndrome?

Down syndrome children

There are over 120 recognized features of Down syndrome but most individuals have only six or seven. Distinctive features may include an enlarged tongue, low muscle tone, upward slant to the eyes, a gap between the large and second toe, a depressed nasal bridge/flat profile, a small nose, abnormally shaped ears, hyper-flexibility, a pinky finger with one flexion furrow, small skin folds on the corner of the eyes and often mild to moderate retardation. What causes Down syndrome is widely understood in the scientific community, but it's not understood exactly why faulty cell division occurs.

An error in cell division is what causes this chromosomal disorder, experts say. Typically, human cells have 46 chromosomes; half from the sperm and half from the egg. Occasionally, extra genetic material builds up on the 21st chromosome when cells divide improperly and chromosome 21 becomes a trio, rather than a standard pair. In fact, another name of Down syndrome is "Trisomy 21." The triple chromosome will then continue to replicate improperly in each growing cell.

To an extent, genetic history may be what causes Down syndrome too. Mothers who have a Down syndrome baby have a 1% risk of having another. A young woman who had two uncles with Down syndrome was told she had a 1/300 risk of having a Down syndrome pregnancy. Four percent of the parents with Down syndrome babies are carriers of the genetic translocation for this syndrome that can be inherited and passed down. If the father is the carrier of rearranged DNA on chromosome 21, then the risk of passing it on is 3%, whereas the risk for a maternal carrier is about 12%. However, it is believed that most cases are not inherited.

During pregnancy, there are several screening tests to examine what causes Down syndrome. Some people get blood tests like the quad screen, which reveals chromosomal disorders between the eleventh and fourteenth weeks of pregnancy. Doctors look for plasma protein-A and the human chorionic gonadotropin hormone. This test is about 87% effective in making a Down syndrome diagnosis. Ultrasound is another method to check for abnormalities. While these tests may give parents peace of mind, they may also set off a false alarm. Even though 1/20 women test positive, most will go on to deliver healthy babies anyway.