1. Down syndrome

2. The risk of Down syndrome and other trisomies increases with the mother’s age. The risk of having a baby with Down syndrome is about (1):
1 in 1,300 at age 25
1 in 1,000 at age 30
1 in 400 at age 35
1 in 100 at age 40
1 in 35 at age 45

3. What causes Down Syndrome?
Down syndrome occurs because of an abnormality characterized by an extra copy of genetic material on all or part of the 21st chromosome. Every cell in the body contains genes that are grouped along chromosomes in the cell's nucleus or center. There are normally 46 chromosomes in each cell, 23 inherited from your mother and 23 from your father. When some or all of a person's cells have an extra full or partial copy of chromosome 21, the result is Down syndrome. The most common form of Down syndrome is known as Trisomy 21, a condition where individuals have 47 chromosomes in each cell instead of 46. This is caused by an error in cell division called nondisjunction, which leaves a sperm or egg cell with an extra copy of chromosome 21 before or at conception. Trisomy 21 accounts for 95% of Down syndrome cases, with 88% originating from nondisjunction of the mother's egg cell. The remaining 5% of Down syndrome cases are due to conditions called mosaicism and translocation. Mosaic Down syndrome results when some cells in the body are normal while others have Trisomy 21. Robertsonian translocation occurs when part of chromosome 21 breaks off during cell division and attaches to another chromosome (usually chromosome 14). The presence of this extra part of chromosome 21 causes Down some syndrome characteristics. Although a person with a translocation may appear physically normal, he or she has a greater risk of producing a child with an extra 21st chromosome.

4. What are the signs and symptoms of Down syndrome?
Intellectual and Developmental Disabilities (IDDs) is a disability that causes limits on intellectual abilities and adaptive behaviors (conceptual, social, and practical skills people use to function in everyday lives).  Most people with Down syndrome have IQs that fall in the mild to moderate range of IDDs.  They may have delayed language development and slow motor development. 
Some common physical signs of Down syndrome include:
Flat face with an upward slant to the eye, short neck, and abnormally shaped ears
Deep crease in the palm of the hand
White spots on the iris of the eye
Poor muscle tone, loose ligaments
Small hands and feet
There are a variety of other health conditions that are often seen in people who have Down syndrome, including:
Congenital heart disease
Hearing problems
Intestinal problems, such as blocked small bowel or esophagus
Celiac disease
Eye problems, such as cataracts
Thyroid dysfunctions
Skeletal problems
Dementia—similar to Alzheimer’s

5. Treatment for Down Syndrome
Because there is no cure, the goals of Down syndrome treatment are to control symptoms and manage any resulting medical conditions. This includes regular checkups and screenings, medications, and surgery. Counseling and support groups are also aspects of treatment for those who need help in coping with the emotional and practical aspects of Down syndrome.

6. Interesting Facts of Down Syndrome
Down syndrome is really the only trisomy compatible with life. Only two other trisomies have been observed in babies born alive (trisomies 13 and 18), but babies born with these trisomies have only a 5% chance of surviving longer than one year.
In 90% of Trisomy 21 cases, the additional chromosome comes from the mother's egg rather than the father's sperm.
Down syndrome is the most common genetic disorder caused by a chromosomal abnormality. It affects 1 out of every 800 to 1,000 babies.
Down syndrome was originally described in 1866 by John Langdon Down. It wasn't until 1959 that a French doctor, named Jerome Lejeune, discovered it was caused by the inheritance of an extra chromosome 21.