Down syndrome is the most common genetic condition in the United States. It occurs in about  1 of every 800 infants with many as 6,000 children born with Down syndrome each year. It is estimated that about 85% of children with Down syndrome will survive the first year and about 50 % will live longer than 50 years old.

What causes Down syndrome ?

It is cause by one of these three abnormal division involving chromosome 21.

• Trisomy 21 : This account for  more than 90% of Down syndrome. An extra chromosome ( chromosome 21) originates in the development of either the egg or sperm. When the egg and sperm unite to form the fertilized egg,  3 rather than 2 chromosome 21 are present. The extra chromosome is repeated in every cell as the cell divides
• Mosaic Trisomy 21 : This is a rare form accounting for less than 2%  of Down syndrome. The difference between this and the simple trisomy 21 is that   the extra chromosome 21 is present in some, but not all cells of the individual.  This type is caused by abnormal cell division after fertilization.
• Translocation Trisomy 21 : This account for about 3 to 4 % of all cases. In this case, part of chromosome 21 becomes attached (translocated) to another chromosome (usually the 13th, 14th or 15th chromosome) before or at conception.The carrier (the one having the translocated chromosome) will have 45 chromosomes instead of 46 but they will have all the genetic material of a person with 46 chromosomes. This is because the extra chromosome 21 material is located on a different chromosome (the translocated one). A carrier will have the extra material but will have only one chromosome 21. He will not exhibit any of the symptoms of Down syndrome because he has the correct amount of genetic material.

Couple with one child with Down syndrome due to translocation trisomy 21, has an increased likelihood of Down syndrome in future pregnancies. This is because one of the parents may be a balanced carrier of the translocation.

Chances of passing the translocation depends on the sex of the parent .  A carrier father has a 3 % risk of passing it on to the child. A carrier mother has 12 % risk.

In  most cases of Down syndrome especially in the case of transolocation trisomy 21, it is important for the parents to get genetic counseling to determine their risk.

What is the risk of having a child with Down syndrome ?

Some of the risks include the following :

• maternal age – there is a high risk of chromosomes dividing incorrectly as a woman ages
• carrier parent – parents  who are carriers of the genetic translocation for Down syndrome have an increased risk . This depends on the type of translocation. People with this condition rarely reproduce. 15 to 30% of women  with trisomy 21 are fertile. They have a 50% chance of having a child with Down syndrome.

There is no evidence of a man with Down syndrome fathering a child.

Screening and diagnosis for Down syndrome

Screening tests

Several screening test can help identify the possibility of Down syndrome. These tests do not provide conclusive answer but the likelihood  of the baby having the condition.

The most common are :

• ultrasound
• blood tests
  • first trimester screen
  • quad marker screen – done between 15 to 20 weeks of pregnancy
  • triple screen – this is done between 16 and 18 weeks of pregnancy

Diagnostic tests

If screening test  are positive or higher for the risk of Down syndrome, further testing may be needed.

Diagnostic tests can help identify Down syndrome. These tests include the following :

• Amniocentesis – performed after 15 weeks
• Chorionic villus sampling CVS – performed between 9  and 14 weeks
• Percutaneous umbilical blood sampling (PUBS) – performed after week 18.

Diagnostic test for newborns

At birth, the initial diagnosis is usually based on the baby’s appearance.  If some or all of the characteristics of Down syndrome are present , the doctor will order a chromosomal karyotype test to be done.  If there is an extra chromosome 21 present, the diagnosis is Down syndrome.

What does a child with Down syndrome look like ?

A child with this condition  has the following features :

• eyes that slant upwards
• a small mouth which makes the  tongue look big
• small ears that fold over a little at the top
• a short neck
• white spots in the iris of the eye
• a small nose with a flattened nasal bridge
• small hands and feet
• low muscle tone
• short statue in childhood and adulthood

Most children with this condition have some but not all the features.

What health problems do children with Down syndrome have ?

Most health problems with Down syndrome are  treatable and the life expectancy is now about 60 years. Some the health conditions they may face include :

• heart defects
• intestinal defects
• vision problems
• hearing loss
• thyroid problems
• leukemia
• microcephaly
• memory loss
• infections

What is the treatment for Down syndrome ?

There is no cure for this condition.  However  children with this condition will benefit from early medical assistance  and developmental interventions beginning during infancy. They may benefit from speech therapy, occupational therapy and  physical therapy. They may also receive special education and assistance in school.

Coping skills

Finding out that your child has  Down syndrome can be scary and difficult. These three actions can help you cope with the situation.

• get a team of professionals : get a team of health care providers, teachers, and therapists that you trust to work with you in providing the best care for your child.
• get support from other families :Joining support groups can be beneficial. You get to meet families with similar experiences. These support groups can be found through local hospitals, physicians, schools and the Internet.
• dont believe the myths about Down syndrome : There’s been a lot of improvement in the lives of people with Down syndrome in recent years.  Most live with their families, go to mainstream schools and have various jobs as adults. People with Down syndrome can lead fulfilling lives.