Down Syndrome Down syndrome is an issue with the chromosomes in a human that not only causes the child stress but additional stress to the parents. The human body is made of cells. All cells contain a center, called a nucleus, in which genes are stored. Genes, which carry the codes responsible for all our inherited characteristics, are grouped along rod-like structures called chromosomes. Normally, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Down syndrome occurs when some or all of a person’s cells have an extra full or partial copy of chromosome 21. The most common form of Down syndrome is known as Trisomy 21. Individuals with Trisomy 21 have 47 chromosomes instead of the usual 46 in each of their cells. The condition results from an error in cell division called non-disjunction. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body. This error in cell division is responsible for 95 percent of all cases of Down syndrome. Having an extra copy of this chromosome means that each gene may be producing more protein product than normal. Cells seem to tolerate this better than having not enough protein, or having altered protein due to a mutation in the DNA sequence. The condition leads to impairments in both cognitive ability and physical growth that range from mild to moderate developmental disabilities. Through a series of screenings and tests,
Down syndrome can be detected before and after a baby is born. The only factor known to affect the probability of having a baby with Down syndrome is maternal age. That is, less than one in 1,000 pregnancies for mothers less than 30 years of age results in a baby with Down syndrome. For mothers who are 44 years of age, about 1 in 35 pregnancies results in a baby with Down syndrome. Because younger women generally have more children, about 75% – 80% of children with Down syndrome are born to younger women. While Down syndrome is often diagnosed shortly after birth, it is also increasingly being diagnosed during pregnancy due to abnormal ultrasound findings, an abnormal result on a blood test done mom, or by amniocentesis or chorionic villi sampling testing. Chorionic villi sampling or CVS is a test done on the placenta between 10 and 12 weeks of pregnancy.
Some of these subtle signs include a decrease in femur length, an increase in the skin behind the neck, or choroid plexus cysts. These are what are often referred to as “soft signs” because none of these ultrasound findings will cause the fetus any problems by themselves. However they may make the doctor suspicious that the fetus has Down syndrome. Other more serious signs that can also be seen on an ultrasound can include heart defects and intestinal blockages. Down syndrome cannot be diagnosed based on ultrasound findings alone. These findings simply suggest that there is a higher risk that the fetus may have Down syndrome. Based on this increased risk, your doctor will recommend that your consider having an amniocentesis or CVS to confirm the diagnosis. It is up to you to decide whether or not to have this testing.
“Common physical signs include:
• Decreased muscle tone at birth
• Excess skin at the nape of the neck
• Flattened nose
• Separated joints between the bones of the skull
• Single crease in the palm of the hand
• Small ears
• Small mouth
• Upward slanting eyes
• Wide, short hands with short fingers
• White spots on the colored part of the eye” (NCBI)
Most of us familiar with Down syndrome know that it brings characteristic facial features and delayed or impaired cognitive development. People with Down syndrome, however, are also more vulnerable than the general population to diabetes, leukemia, and infectious and autoimmune disease and about 40% are born with heart defects. For most of history, then, the life expectancy of people with Down was very low but, with advances in knowledge and access to health care, life expectancy has risen dramatically… especially for white people:

(the society pages)
From the beginning of their reproductive life women have the option to reduce the Down syndrome risk by completing their family by age 30. On a population level this strategy could more than halve the birth prevalence of this disorder. Women with a high a prior Down syndrome risk because of an inherited translocation or a previous pregnancy with a non-inherited form of Down syndrome should have access to Pre-implantation genetic diagnosis (PGD). The effectiveness of this technique is limited by the availability of normal embryos in such families but reasonably high pregnancy rates are achievable with an extremely low risk of a Down syndrome birth. However, only about 1% of Down syndrome pregnancies are in women with a family history of the disorder so the impact of this activity on birth prevalence is minimal. In some localities women of advanced reproductive age also have access to PGD which could potentially have a much greater impact on prevalence. Biochemical, molecular and epidemiological evidence suggests a link between Down syndrome and a defect in foliate and methyl metabolism. This is not sufficient to justify an active preventative strategy of folic acid supplementation without performing a large clinical trial. “However, current supplementation policies designed to prevent NTDs (neural tube defects) may incidentally prevent Down syndrome, provided a sufficiently high dose of folic acid and possibly cobalamin is used.” (Med sci) Further progress in the primary prevention of Down syndrome is hampered by limited knowledge of the cause of this disorder. There is an urgent need to refocus research in that direction.

References http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001992/ http://thesocietypages.org/socimages/2010/05/03/the-life-expectancy-of-people-with-downs-syndrom/
http://www.medsci.org/v02p0093.htm