2. Down Syndrome
Down syndrome is the most common cause of mental retardation and malformation in a newborn. A genetic disorder, it occurs because of the presence of an extra chromosome.
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3. Down Syndrome
Down syndrome is a set of physical and mental traits caused by a gene problem that happens before birth. Children with Down syndrome tend to have certain features, such as a flat face and a short neck. They also have some degree of...
Healthline.com (OMS Preferred Provider)

4. Down Syndrome: MedlinePlus
Down syndrome is set of mental and physical symptoms that result from having an extra copy of chromosome 21. Even though people with Down syndrome may have some physical and mental features in common, symptoms of Down<...
MedlinePlus (Offsite)

5. Down syndrome
In most cases, Down syndrome occurs when there is an extra copy of chromosome 21. This form of Down syndrome is called Trisomy 21. The extra chromosome causes problems with the way the body and brain develop.
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6. Down Syndrome
Screening tests can be done to work out the chance that your baby has Down syndrome. The tests are not compulsory - not all women choose to have them.
www.healthinsite.gov.au

7. Down Syndrome
Down syndrome is a developmental disorder caused by an extra copy of chromosome 21 (which is why the disorder is also called "trisomy 21"). Having an extra copy of this chromosome means that each gene may be producing more protein product than nor...
learn.genetics.utah.edu

8. Down syndrome
Down syndrome was named after John Langdon Down, the first physician to identify the syndrome.  It is the most frequent genetic cause of mild to moderate intellectual and developmental disabilities.
rarediseases.info.nih.gov

9. Down Syndrome
You have probably seen people who have Down syndrome. They have certain physical features, such as a flatter face and upward slanting eyes.
kidshealth.org

10. Down Syndrome
Down syndrome is set of mental and physical symptoms that result from having an extra copy of Chromosome 21. 
www.nichd.nih.gov