Blog For Down Syndrome

What are trisomies?

The term “trisomy” is used to describe the presence of three chromosomes in a pair. For example, if a baby is born with three #21 chromosomes, rather than the usual pair, the baby would be said to have “trisomy 21,” also known as Down syndrome. Other examples of trisomy include trisomy 18 and trisomy 13. Again, trisomy 18 or trisomy 13 simply means there are three copies of the #18 chromosome (or of the #13 chromosome) present in each cell of the body, rather than the usual pair.

What is Down syndrome?

Down syndrome is a chromosomal disorder that includes some degree of mental retardation, as well as a combination of birth defects, including neurologic impairment, characteristic facial features and, often, heart defects and visual and hearing impairment. The severity of all these problems varies greatly among affected individuals. Down syndrome is one of the most common genetic birth defects, affecting approximately one in 800 to 1,000 babies. According to the National Down Syndrome Society, there are approximately 350,000 individuals with Down syndrome in this country. Life expectancy among adults with Down syndrome is about 55 years, though average life span varies.The name “Down syndrome” comes from the physician Dr. Langdon Down, who first described the collection of findings in 1866. It was not until 1959 that the cause of Down syndrome (the presence of an extra #21 chromosome) was identified.

What causes Down syndrome?

Normally in reproduction, the egg cell of the mother and the sperm cell of the father start out with the usual number of 46 chromosomes. The egg and sperm cells undergo cell division, in which the 46 chromosomes are divided in half and the egg and the sperm cells end up with 23 chromosomes each. When a sperm with 23 chromosomes fertilizes an egg with 23 chromosomes, the baby ends up with a complete set of 46 chromosomes, half from the father and half from the mother.Sometimes, an error occurs when the 46 chromosomes are being divided in half and an egg or sperm cell keeps both copies of the #21 chromosome, instead of just one copy. If this egg or sperm is fertilized, the baby ends up with three copies of the #21 chromosome and this is called “trisomy 21″ or Down syndrome. The features of Down syndrome are a result of the extra copy of chromosome 21 in every cell in the body.A child is born with Down syndrome due to trisomy 21 in 95 percent of cases. In these cases, there is a 17 percent chance for parents to have another child with a trisomy. It doesn’t, however, increase the risk of having a child with any other birth defect, nor does it increase the risk for any relative to have a child with Down syndrome.

Occasionally, the extra chromosome 21 is attached to another chromosome in the egg or sperm; this may result in what is called “translocation” Down syndrome (3 to 4 percent of cases). This is the form of Down syndrome that can be inherited from a parent. Some parents have a rearrangement called a balanced Robertsonian translocation, in which the #21 chromosome is attached to another chromosome, but it does not affect his or her health. Rarely, a form of Down syndrome called “mosaic” Down syndrome may occur when an error in cell division occurs after fertilization (1 to 2 percent of cases). These people have some cells with an extra chromosome 21 and others with the normal number.

What does a child with Down syndrome look like?

A child with Down syndrome may have eyes that slant upward and small ears that may fold over slightly at the top. His or her mouth may be small, making the tongue appear large. The nose also may be small, with a flattened nasal bridge. Some babies with Down syndrome have short necks and small hands with short fingers. Most children with Down syndrome will have some, but not all, of these features.

What types of problems do children with Down syndrome typically have?

About 40 to 50 percent of babies with Down syndrome have heart defects. Some defects are minor and may be treated with medications, while others may require surgery. All babies with Down syndrome should be examined by a pediatric cardiologist, a physician who specializes in heart diseases of children, and have an echocardiogram (a procedure that evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and heart valves) in the first two months of life, so that any heart defects can be treated.

About 10 percent of babies with Down syndrome are born with intestinal malformations that require surgery.

More than 50 percent have some visual or hearing impairment. Common visual problems include strabismus (crossed eyes), near- or farsightedness and cataracts. Most visual problems can be improved with glasses, surgery or other treatments. A pediatric ophthalmologist (a physician who specializes in comprehensive eye care and provides examinations, diagnosis and treatment for a variety of eye disorders) should be consulted within the first year of life.

Children with Down syndrome may have hearing loss due to fluid in the middle ear, a nerve defect or both. All children with Down syndrome should have regular vision and hearing examinations so any problems can be treated before they hinder development of language and other skills.

Children with Down syndrome are at increased risk of developing thyroid problems and, occasionally, leukemia. They also tend to have many colds, as well as bronchitis and pneumonia. Children with Down syndrome should receive regular medical care, including childhood immunizations. The National Down Syndrome Congress publishes a “Preventative Medicine Checklist” that outlines which checkups and medical tests are recommended at various ages.

How serious is the neurologic impairment that accompanies Down syndrome?

The degree of neurologic impairment/developmental delay/mental retardation that accompanies Down syndrome varies widely. However, most IQ scores fall within the moderate to mild (60 to 75) range. Further, studies suggest that, with proper intervention, fewer than 10 percent will have severe mental retardation. There is no way, however, to predict the mental development of a child with Down syndrome based on physical features. The severity of mental retardation is defined by IQ (intelligent quotient) point ranges:

What can a child with Down syndrome do?

Children with Down syndrome can usually do most things that any young child can do, such as walking, talking, dressing and being toilet trained. However, they generally do these things later than other children. The exact age that these developmental milestones will be achieved cannot be predicted. Early intervention programs, beginning in infancy, can help these children achieve their individual potential.

Can a child with Down syndrome go to school?

Yes. There are special programs beginning in the preschool years to help children with Down syndrome develop skills as fully as possible. Along with benefiting from early intervention and special education, many children can be integrated into the regular classroom (mainstreamed). Many will learn to read, write and participate in diverse childhood activities, both at school and in their neighborhoods. Today, an increasing number of adults with Down syndrome live in community group homes, where they take care of themselves, participate in household chores, develop friendships, partake in leisure activities and work in their communities.

Can people with Down syndrome marry?

Some people with Down syndrome marry. Although there have been rare exceptions, men with Down syndrome cannot father a child. In any pregnancy, a woman with Down syndrome has a 50/50 chance of conceiving a child with Down syndrome.

How is Down syndrome diagnosed?

Physicians can sometimes determine by physical examination that a child has Down syndrome. However, to confirm the diagnosis, a small blood sample should be taken and the chromosomes analyzed to determine the presence of an extra #21 chromosome. This information is important for determining the recurrence risk.Chromosomal abnormalities such as Down syndrome can often be diagnosed before birth by analyzing cells in the amniotic fluid (amniocentesis) or from the placenta (chorionic villius sampling). Fetal ultrasound during pregnancy can also determine if the child has certain physical findings associated with Down syndrome, but can’t make a definitive diagnosis. A chromosome analysis, whether performed on a blood sample, cells from the amniotic fluid or placenta, is more than 99.9 percent accurate.

What are the maternal age risks for Down syndrome?

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

In general, for women under 40 (after having one child with Down syndrome), the chance of having another baby with Down syndrome is 1 percent. The chance for Down syndrome is also known to increase with the mother’s age and, after age 40, a mother would simply have the risk based on her age at delivery. It is important to know that about 75 percent of babies with Down syndrome are born to women under 35; this is because women under 35 simply have more babies than women over 35. Your physician may refer you to a genetic physician or genetic counselor who can explain the results of chromosomal tests in detail, including what the recurrence risks may be in another pregnancy and what tests are available to diagnose chromosome problems before a baby is born.

Can Down syndrome be cured or prevented?

There is no cure for Down syndrome. We are not certain how to prevent the chromosomal error that causes Down syndrome. To date, there is no reason to believe that a parent could have done anything to cause or prevent the birth of their baby with Down syndrome.Some claim that various high-dose vitamins given to children with Down syndrome will improve mental performance and lessen mental retardation. To date, however, there has not been a medical study to prove this actually works. It is important for new families to talk to their physician, other families and the National Down Syndrome Congress to learn what to expect with Down syndrome and to learn about things that may be helpful in raising a child with Down syndrome.

What research is being conducted on Down syndrome?

The March of Dimes is investigating why errors in chromosome division occur, in the hope of someday preventing Down syndrome and other birth defects caused by abnormalities in the number or structure of chromosomes. Other researchers are seeking to improve the outlook for children with Down syndrome. One example of this includes developing improved language intervention programs to help these children communicate more easily.

Where can families affected by Down syndrome get additional information?

Several organizations across the country provide information and support for families with children affected by Down syndrome. Browse this web site for additional information.