Diagnosic method Diagnosic method A newborn baby with Down syndrome

often has physical features a flat facial profile an upward slant to the eye a short neck abnormally shaped ears white spots on the iris of the eye

Diagnostic method Diagnostic method blood test called a chromosomal karyotype This involves "growing" the cells from the ba

by's blood for about two weeks, followed by a microscopic visualization of the chromosomes to determine if extra material from chromosome 21 is present.The baby is down syndrome.

checking the mother’s blood There are three independent measurements: alpha-fetoprotein (A

FP), unconjugated estriol (uE3) and human chorionic gonadotropin (hCG).

Alpha-fetoprotein is made in the part of the uterus called the yolk sac and in the fetal liver, and some amount of AFP gets into the mother's blood. In neural tube defects, the skin of the fetus is not intact and so larger amounts of AFP is measured in the mother's blood. In Down syndrome, the AFP is decreased in the mother's blood, presumably because the yolk sac and fetus are smaller than usual.

Estriol is a hormone produced by the placenta, using ingredients made by the fetal liver and adrenal gland. Estriol is decreased in the Down syndrome pregnancy. This test may not be included in all screens, depending on the laboratory.

Human chorionic gonadotropin hormone is produced by the placenta, and is used to test for the presence of pregnancy. A specific smaller part of the hormone, called the beta subunit, is increased in Down syndrome pregnancies.

consideration in the screening test is the age of the fetus (gestational age).

Other diagnostic methodsOther diagnostic methodsThese tests include amniocentesis, ch

orionic villus sampling (CVS), and

percutaneous umbilical blood sampling (PUBS).

Amniocentesis Amniocentesis Is the removal and analysis of a small sample

of fetal cells from the amniotic fluid, is widely available and involves a lower risk of miscarriage than chorionic villus sampling. However, amniocentesis cannot be done until the 14th to 18th week of pregnancy, and it usually takes additional time to determine whether the cells contain extra material from chromosome 21.

Side effects to the mother include cramping, bleeding, infection and leaking of amniotic fluid afterwards

slight increase in the risk of miscarriage

Chorionic villus sampling Chorionic villus sampling

Conducted at 9 to 11 weeks of pregnancy, involves extracting a tiny amount of chorionic villi, tissue extensions that will eventually develop into a placenta. The tissue can be tested for the presence of extra material from chromosome 21. The villi can be obtained through the pregnant woman's abdomen or cervix. This type of sampling carries a 1-2% risk of miscarriage.

percutaneous umbilical blood sampling or PUBS percutaneous umbilical blood sampling or PUBS

Is the most accurate method and can be used to confirm the results of CVS or amniocentesis. However, PUBS cannot be performed until later in the pregnancy, during the 18th to 22nd weeks, and carries the greatest risk of miscarriage.

New prenatal diagnostic techniquesNew prenatal diagnostic techniques

Are currently being developed. The NICHD has supported the development of a new, noninvasive test performed during the first trimester of pregnancy, that samples and separates fetal cells from the mother's blood. The goal is to compare the accuracy of this type of cellular level analysis with results obtained by amniocentesis or CVS.

most frequently occurring chromosomal abnormality occurs once in about every 800 to 1000 live births and in families from all social, economic, cultural, religious and racial backgrounds

there are approximately 80 newborn babies in Hong Kong found to be suffered from Down syndrome each year

if a couple has a child with Down syndrome, there is usually an increased risk for a second affected child

the likelihood of this occurring increases with the age of the mother

Low intelligence Flattened back of head Slightly shortened fingers The little finger curves inward Some have open-heart surgery, then make a chest scar after

operation

a genetic abnormality caused by the presence of extra chromosome 21 materials

was named after john Langdon down, a British physician, who first described it in 1866

cause of this condition is still unknown there are three types of chromosomal patterns th

at result in Down syndrome. They are trisomy 21, translocation and mosaicism

most common (95%) due to a mutation in chromosome number caused by meiotic non-disjunction (i.e. unequal

chromosome division)of the chromosome pair 21 during the production of ova

Fusion of ovum, which contain 24 chromosomes, with normal sperm having 23 chromosomes, will result in offspring having 47 chromosomes in all cell

less common (3-5%) due to a mutation in chromosome structure cause by the translocation of part or all of chrom

osome 21 to another chromosome, usually 14 indistinguishable from individuals with the trisom

y 21 form

approximately 2% of people A faulty cell division occurs in one of the early cell divisi

on after conception, resulting in some cells having 46 chromosomes and some having 47

the percentage of cells with 47 chromosomes instead of 46 varies from person to person. Those cells with 47 chromosomes contain an extra 21st chromosome

Because of the “mosaic” pattern of the cells, the term mosaicism is used

Evaluating family history and medical record Ordering genetic tests Evaluating the results of this investigation Helping parents understand and reach decisions

about what to do next

Genetic counseling is the process of:

CounselingCounseling

While caring for a child with Down syndrome frequently requires more time and energy, parents of newborn children with Down syndrome should seek the advice of a knowledgeable pediatrician and/or the many Down syndrome support groups and organizations available.So they have already to care the children who have down syndrome

Detect the risk of having a specified fetal abnormality

Limitation of the diagnostic test

Conveyed to the couple in a manner they can understand

Options open to the couple should a fetal abnormality is detected

Example of counseling centerExample of counseling center Administration on Developmental Disabilities

Administration for Children and FamiliesU.S. Department of Health and Human ServicesMail Stop: HHH 300F370 L’Enfant Promenade S.W.Washington, DC 20447(202) 690-6590

http://www.acf.dhhs.gov/programs/add/ http://www.acf.dhhs.gov/programs/add/

American Speech, Language and Hearing Association10801 Rockville PikeRockville, MD 208521-800-638-8255 or 1-888-321-ASHA

http://www.asha.org/ http://www.asha.org/

Learning Disabilities Association of America4156 Library RoadPittsburgh, PA 15234-1349(412) 341-1515 or 1-888-300-6710

http://www.ldanatl.org/ http://www.ldanatl.org/ March of Dimes

1275 Mamaroneck AvenueWhite Plains, NY 10605(914) 428-71001-888-MODIMES (1-888-663-4637)

http://www.modimes.org/ http://www.modimes.org/

More counseling center:http://www.nichd.nih.gov/publications/pubs/downsyndrome/down.htm - AdditionalResources

Down syndrome Cystic fibrosis Tay-Sachs disease (a fatal disease affecting the ce

ntral nervous system)

These tests identify the likelihood of passing certain genetic diseases or disorders (those caused by a defect in the genes - the tiny, DNA-containing units of heredity that determine the characteristics and functioning of the entire body) to your children.

Genetic disorders are: