Down’s Syndrome Essay, Research Paper

Down’s Syndrome

Down’s syndrome is a genetic condition involving an extra chromosome,

this change occurs around the time of conception. A person with Down’s syndrome

has forty-seven chromosomes instead of the usual forty-six. A relatively

common genetic disorder, Down’s strikes 1 out of 600 babies. In 95 percent of

all cases, the disorder originates with the egg, not the sperm, and the only

known risk factor is advanced maternal age-at age 35, a woman has 1 chance in

117 of having a baby with Down’s; at 40, her odds are 1 in 34. (Graves, 1990)

People with Down’s syndrome all have a certain degree of learning

disability . This means that they develop and learn more slowly than other

children. However, most children with Down’s syndrome today will walk and talk,

many will read and write, go to ordinary school, and look forward to a semi-

independent adult life. (Platt and Carlson, 1992)

Facts on Down Syndrome

*Down syndrome is not a lethal anomaly. One to two percent of persons

born with this disorder have uncorrectable heart defects at birth. The average

life expectancy for all others is now beyond age 55 years.

*Today less than 5% of persons with Down syndrome have severe-to-

profound mental retardation. The majority are on the border of mild-to-moderate

mental retardation, and some are exhibiting normal IQ scores today.

*The average reading level for persons with Down syndrome is 3rd grade,

with many reading at 6th-12th grade levels today.

*The vast majority of adults with Down syndrome today can be expected to

live semi- or totally independently and many enter the work force with today’s

supported employment programs and some are competitively employed.

Some medical conditions that demand special attention for people with

Down syndrome include:

*Congenital Heart Disease: usually in the form of endocardial cushion

defects, affects 40% of babies and should be screened for by echocardiography

soon after birth as it may well be difficult to detect.

* Gastrointestinal disorders: the most common congenital abnormality of

the gastrointestinal tract associated with Down syndrome is duodenal atresia,

although pyloric stenosis, Hirschsprung’s disease and tracheo-oesophageal

fistulae have all been reported.

* Vision: Three percent of newborns with Down syndrome will have dense

congenital cataracts which should be removed early. Glaucoma is also common.

* Congenital Hypothyroidism: This condition is slightly more prevalent

in babies with Down syndrome. It should be detected by the routine heelprick

screen performed on all babies.

*Congenital dislocation of the hips: Joint laxity and hypotonia can

combine to increase the incidence of hip dislocation, although true congenital

dislocation is quite rare.

* Sensory deficits: Significant hearing impairments occur in the

majority of children with Down syndrome. Annual audiometry and specialist

consultation is recommended.

* Atlantoaxial instability: Up to 15% of children with Down syndrome

will have evidence of instability of the atlantoaxial joint but in only a

handful of cases will this instability result in an impingement on the spinal

cord with resultant neurological signs.

* Physical growth: Physical development is invariably delayed in

children with Down syndrome. A tendency towards obesity requires special

attention to healthy diet and exercise habits in this group.

* Dental care: The teeth of children with Down syndrome tend to be small,

irregularly spaced and misshapen. Early and frequent dental care is required to

ensure adequate dentition for adult life.

* Psychiatric disorders: Psychiatric illnesses occur in people with Down

syndrome with much the same frequency as in the rest of the population.

*Dementia: Much recent attention has been focused on the association

between Down syndrome and Alzheimer’s disease. There appears to be a gene-dose

effect where having an extra chromosome 21 gives an individual a higher chance

of developing Alzheimer’s disease. (Newton, 1992)

A significant amount of research has been conducted on Down syndrome, in

particular many methods to detect Down syndrome in fetuses have been developed.

This is a controversial issue for researchers and for families who have Down

syndrome children and adults. The following is a discussion of some of the

detection methods for Down syndrome, and the facilities in which they were


Jones Institute

Scientists at Norfolk’s Jones Institute for Reproductive Medicine say

they have overcome most technical hurdles to screening embryos for Down syndrome

and many other chromosomal defects before the embryos are implanted in a woman’s


The institute, part of Eastern Virginia Medical School, hopes to try out

the technique with a handful of high-risk couples who come to the institute for

in-vitro fertilization, in the near future. (www #1)

Eventually, all couples who go through the Jones Institute may have the

option to screen for Down and most of the other conditions caused by an extra

chromosome on one of 23 pairs that make up the normal complement. The technique

has been developed in part to help parents avoid a difficult moral decision -

what to do if the fertility techniques cause the mother to become pregnant with

many children at once. At the same time, it opens up a host of other ethical

questions for parents and society as a whole, say people who have children with

Down. (www #1)

According to Kingsley and Levitz (1994), in-vitro fertilization (IVF),

is a technique in which eggs are removed from a woman’s ovaries and combined

with sperm in a dish. The resulting embryos are transplanted into the woman’s

uterus. Before transplant, a single cell will be removed and exposed to probes

made up of genetic material treated with fluorescent dye. Each probe has been

designed to attach to a specific chromosome in the nucleus. Using a special

microscope, a scientist can count the dots of various colors. Three of a

specific color means that there is one extra chromosome of that type.

The institute will test five pairs that account for most chromosomal

defects. The first cases will be done for free. When the procedure becomes

common, the procedure will add about $2,000 to the cost of IVF, about $7,500.

The Chairman of reproductive endocrinology at the Jones Institute said the

procedure was developed primarily to avoid the multiple births that sometimes

happen with IVF. (www #1)

Most transplanted embryos, and many naturally conceived ones, never take

root and grow because they have the wrong number of chromosomes. In IVF, doctors

try to improve the odds by implanting three or more, assuming that some will be

lost. But sometimes, many or all of the embryos are viable. The parents then

must decide – do they selectively abort some, or do they take on the hugely

demanding task of having many babies at once? If doctors could screen the

embryos, he said, they could limit themselves to implanting two and still enjoy

a high probability that the embryos will survive.

Nevertheless, the ability to screen out embryos with Down syndrome still

worries families of people with the condition. (www #1)

The option not to have a child with Down already exists. Tests during

pregnancy can detect the condition. Parents may choose an abortion. Parents of

children with Down syndrome, say that other parents who choose to discard an

embryo in a laboratory are further removed from the implications of their

decision. Doctors at the medical center say that they want very much for people

confronting the decision to understand that having a child with Down syndrome

can be very fulfilling. They says the Jones Institute isn’t trying to devalue

people with Down syndrome by offering the test. But they say this information

has such important ramifications for the family, if we have that information, we

would give it to them and they make the choice.

Polar Body Analysis

Physicians at Illinois Masonic Medical center have discovered that they

can determine if a woman will have a baby with Down’s syndrome before she gets

pregnant, provided she is willing to undergo in-vitro fertilization. Using an

experimental technique called polar body analysis, the genetic material of an

egg can be checked before laboratory fertilization, helping some women avoid


Chicago researchers at Masonic reported on a yearlong study involving

100 women who underwent the polar body procedure, they say that several women

already have delivered healthy babies, and more than 20 are pregnant with no

sign of Down’s.

But the possibility exists that the Masonic patients could have achieved

the same results without genetic testing. The majority of women who have

conventional in-vitro fertilization are older and have normal pregnancies. Dr.

Charles Strom, director of medical genetics at the hospital said that, polar

body work gives a 35-year-old female the same chance of conceiving a

chromosomally normal baby that a 21-year-old has. He said at least half the

women in the in-vitro fertilization program are 35 or older. (www #2)

Polar body analysis hinges on basic biology. During normal development,

the human egg contains a sac of excess chromosomes called the polar body before

it gets ready to be fertilized by a male’s sperm. Since this sac, is a mirror

image of the egg, the genetic content of the egg itself can be determined

through this procedure. (www #3)

Without such testing, about 30 percent of the Down’s pregnancies

resulting from in-vitro fertilization would have miscarried naturally, and

others could have been picked up by the standard prenatal testing techniques,

chorionic villi sampling and amniocentesis.

In-vitro fertilization is expensive, labor intensive and often

disappointing. The polar body test would add another $2,000 to $2,500 to its

costs. (www #2)

The Triple Screen

The “triple screen for Down syndrome” has been in existence for over

five years. However, just this past year, the American College of Obstetricians

and Gynecologists officially recommended that this test be offered to all

pregnant patients of all ages. This implies a legal mandate to practicing

physicians who cannot afford the liability of not offering such a test after a

national recommendation has been made. This “mandate” has been met with great

controversy. (www #3)

The “triple screen” actually involves drawing maternal blood to test for

serum levels of three hormones: human chorionic gonadotropin (HCG),

alphafetoprotein (AFP), and estriol (E3). The pattern of the levels of these

hormones predicts the presence of Down syndrome in the fetuses in up to 60-70%

of pregnancies affected. By using computer formulas, the hormonal levels can be

found that are predictive for a risk of Down syndrome in the fetus that

approximates 1 in 190 – which is the same risk that a pregnant woman has at age

35. Thus, the test has been recommended now for women at all ages. If it is

“positive”, it should be followed by ultrasonography and then amniocentesis to

make a definitive diagnosis. (www #3)

Some uses of the triple screen are seen as positive by all. If the test

is negative, these results can prevent further unnecessary ultrasonography, or

amniocentesis, or chorionic villus sampling – for women 35 or over; or for the

woman with a previous fetus with Down syndrome. Normally these more expensive

and invasive tests would have been recommended in those settings.

It is the use of the test for all pregnant women that begins to stir

controversy. Only one such serum test has ever been recommended so widely before

- the serum (AFP) alphafetoprotein screen. It is a screening test for multiple

types of fetal defects that affect the “neural tube” in the fetus. These defects

include such problems as anencephaly, holoprosencephaly, or einencephaly, as

well as many levels of spina bifida. Down syndrome is certainly not the same as

the wide range of anomalies termed “neural tube defects,” but the Triple Screen

makes it seem an equal to many lethal defects.

The triple screen actually detects many more fetal anomalies than Down

syndrome, including the AFP-related anomalies mentioned above and several lethal

trisomies, such as Trisomy 18. The Triple Screen is called a screen “for Down

syndrome” for marketing reasons, as much as for scientific accuracy.

The Triple Screen is, in fact, a very poor screen, identifying only

about 65% of fetuses with Down syndrome in utero. No other screen with such low

validity has been universally recommended for all pregnant women. Such a

recommendation means billions of dollars for the genetics industry and the

researchers involved. (www #3)

The screening tests establish the probability of pregnant women having

children with Down Syndrome or Spina Bifida and other neural tube defects. It is

possible the widespread use of genetic screening for the purpose of

identification and abortion of fetuses with Down Syndrome may adversely affect

the quality of life for all persons with Down Syndrome in the community.

Many groups representing people with Down syndrome have expressed their

feelings about this issue, the following is a summary of some of the wishes they

have expressed.

1. The primary goal of prenatal genetic testing should not be to reduce

the birth prevalence of Down Syndrome in the population. Its use should be

directed towards the provision of improved health care. 2.Prenatal genetic

testing should be voluntary. The woman or couple should receive counseling

that is comprehensive and provided in a language that is easily understood

by them. Prior to reviewing written consent for prenatal testing, the couple

should be given accurate and up-to-date information on all relevant issues

surrounding prenatal genetic testing and Down Syndrome. This information

should be provided in a balanced manner. Each woman or couple should

be allowed to decide whether prenatal genetic testing is appropriate for

them based on informed choice. An appropriate period of time should be

allowed between receiving information and deciding, with written

consent whether or not to proceed with the test. 3. Following a test result

which implies that the fetus may have a probability of a chromosone

abnormality such as Down Syndrome, the woman or couple should be

provided with detailed, balanced information regarding the options

available to them. This information should be provided by a

knowledgeable and qualified health care provider such as those found

in accredited genetic centres. Balanced information should be so

recorded for the woman or couple to review at their leisure.

Opportunities to have the woman or couple speak to parents of

children with Down Syndrome should be offered. (www #4)

It is evident that the debate over screening for Down syndrome is far

from settled. It is also evident that people with Down syndrome can make an

important contribution to our society. I think if parents are not prepared to

take on the challenges of a child with Down syndrome they should have options,

should one of these options be abortion?

I would have a hard time supporting someone’s decision to abort, especially

having spent some time with a young boy who has Down syndrome.

There are many support groups for families who have children with Down

syndrome, there are also many families willing to adopt. The programs at school

for these children are very adaptable to the needs of the individual. Most

children with Down syndrome can go to school and get along well, they make a

valuable contribution to the classroom and their fellow students. The decision

is a difficult one and I think that there are many options that need to be

explored before anyone can make an informed decision.


Cooley, W. and Graham, J. (1991). Down syndrome – an update and review for the

primary paediatrician. Clin Paed 30 (4): 233-253.

Graves, P. (1990). The intellectually disabled child in Robinson MJ practical

paediatrics 2nd ed. Melboune: Churchill Livingstone.

Kingsley, J. and Levitz, M. (1994). Count us in: Growing up with down syndrome.

New York: Harcourt Brace & Company.

Newton, R.(1992). Down’s syndrome. London: Optima.

Platt, L. and Carlson, D.(1992). Prenatal diagnosis – when and how? NEJM 327


Pueschel, S.(1990). Clinical aspects of down syndrome from infancy to

adulthood. Am J Med Gen Supp 7: 52-56

Pueschel, S. and Pueschel, J. (Eds) (1992). Biomedical concerns in persons with

down syndrome. Baltimore: Paul H Brookes Co.

Pueschel, S. (1992). A longitudinal study of atlanto-dens relationships in

asymptomatic individuals with Down syndrome. Paediatrics 89 (6) pg. 1194-


Selikowitz, M.(1990). Down Syndrome – the facts. Oxford:Oxford University Press.

Stray-Gundersen, K. (Ed.) (1995). Babies with down syndrome: A new parents’

guide (2nd edition). Rockville, MD: Woodbine House.

Tingey, C. (Ed.) (1988). Down syndrome: A resource handbook. Boston, MA:

College- Hill Press.

www #1.

www #2.

www #3. http://wwwpino/ds/prenata/nsdcapf.html

Додати в блог або на сайт

Цей текст може містити помилки.

A Free essays | Essay
25.3кб. | download | скачати

© Усі права захищені
написати до нас