According to the U.S. National Down Syndrome Society, currently one in every 733 babies born each year is diagnosed with Down syndrome. Simply put, Down syndrome is a condition caused by an abnormality in a person's chromosomes. When a child is conceived, he receives strands of DNA, or chromosomes, from his parents. A healthy child will get 23 chromosomes from each parent, or 46 chromosomes total. In most cases of Down syndrome, though, a baby receives an extra copy of chromosome number 21 from one of his parents. There are several theories for why this chromosomal anomaly occurs, among them nondisjunction, which accounts for 95% of all Down's cases, translocation, which is thought to account for 4 to 5% of all cases, and mosaicism, which accounts for about 1%. Research has shown that nondisjunction, the most common reason thought to lead to Down Syndrome, is influenced by maternal age. Statistically, a woman at age 25 has a 1 in 1,250 risk of having a baby with Down Syndrome. At age 30, the risk is about 1 in 900, by age 35 it's about 1 in 350, by age 40 it's 1 in 100, and by 45 it's about 1 in 30. Interesting to note, that even though the risk is greater as the mother's age increases, about 80% of babies with Down syndrome are born to women under age 35. This is because younger women have more babies than older women. It is this extra chromosome that causes the physical and mental delays characteristic of Down syndrome. Physically, people with Down syndrome tend to share certain physical features, such as upward slanting eyes, flat facial profiles, a protruding tongue, small stature, low set ears, and a single deep crease across each palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees or not at all. Mentally, children with DS tend to have IQs that fall in the mild to moderate range of mental disability, though it's important to note that there is more to intelligence than what is tested for with IQ tests. Unfortunately, people with this disorder also tend to be at greater risk for OTHER serious medical conditions, like heart defects, which affects 35 - 50% of Down's patients. Children with DS are also more likely to have hearing and vision problems, leukemia, and thyroid conditions. Knowing all this, some parents-to-be decide to test for Down syndrome before their baby's birth. To do so, they can employ screening tests, diagnostic tests, or a combination of both. One of the most common screening tests is known as the nuchal translucency test, or NT. Which is an ultrasound that measures the nuchal fold, which is the clear space in the tissue at the back of a developing baby's neck. Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average. The NT scan must be done when you're between 11 and 14 weeks pregnant. It's usually offered along with a blood test in what's known as first-trimester combined screening. It's important to understand that these screening tests only measure whether a baby is likely to have DS they do not offer a definitive diagnosis. For this reason, some parents decide to undergo more conclusive diagnostic tests. One diagnostic test is called chorionic villus sampling, or CVS, and involves extracting a small piece of a woman's placenta for testing. Chorionic villus sampling is usually performed between the 10th and 12th weeks of pregnancy. Because CVS is an invasive test, there's a small risk about 1 in 100 that it can induce a miscarriage. Another test, called amniocentesis, involves collecting and testing a sample of the mother's amniotic fluid. It's generally performed between weeks 16 and 18 of a woman's pregnancy. The doctor inserts a hollow needle into the woman's abdomen to remove a small amount of amniotic fluid from around the developing fetus. This fluid contains the baby's chromosomes, and can be tested to check for genetic problems and to determine the sex of the child. Amniocentesis also carries a slight risk of inducing a miscarriage, which ranges from 1 in 200 to 1 in 1,000. For both diagnostic tests, MUCH depends on the skill and experience of the person performing the test, ask what the individual doctor's rate of miscarriage is before consenting to do the test with him or her. After birth, a simple blood test can confirm a diagnosis of Down syndrome, if necessary. While DS can be scary, the life expectancy of people with the disorder is increasing all the time: from 25 in 1983 to 60 today, according to the National Down Syndrome Society. People with DS can often go to school, work, live semi-independently and even get married. The best way to ensure a bright future like this is to get early intervention for your child. One-on-one work with early childhood educators... and speech, occupational, and physical therapists, can ALL help encourage development. Remember: If you are parent to a child with Down syndrome, you are NOT alone some 250,000 Americans have DS! Help your child and help yourself! by becoming as educated about Down syndrome as possible!