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5 Important Facts About Down Syndrome

October 14, 2010

October has arrived, which means Down Syndrome Awareness month is finally here. In order to celebrate this extraordinary time of year here are 5 important facts everyone should know about Down syndrome.

It is the most common chromosomal disorder in the world

According to the National Down Syndrome Society’s (NDSS) website, Down syndrome is the most common chromosomal disorder in the world. Approximately 1 in every 733 babies is born with Down syndrome, representing approximately 5,000 births per year in the United States.

NDSS reports that approximately 6 million people in the world and more than 400,000 people in the United States currently have Down syndrome.

Down syndrome occurs at conception

According to Len Leshin, M.D., a general pediatrician in Corpus Christi, Texas and clinical advisor to the NDSS, “Down syndrome occurs at conception, so nothing in the pregnancy can cause Down syndrome to occur.”


Sperm cell fertilizing the zygote (AKA: conception). Scott Maxwell's Flickr

Average life expectancy for someone with Down syndrome is 60

The NDSS reports that the life expectancy for someone with Down syndrome has increased significantly since 1983, when these individuals were not expected to live past age 25. Today the average person with Down syndrome can live to be upwards of 60-years-old.

80% of babies with Down syndrome are born to women under 35

Even though the likelihood of having a child with Down syndrome increases with the mother’s age more children are being born to younger women (under 35-years-old).

It is much more common for babies with Down syndrome to be born to women over 35 years of age. According to Leshin, “women under 35 have a higher birth rate. No risk factors have been found yet for women under 35 years of age, but several research groups are looking at this question.”

The NDSS’s website lists the likelihood of giving birth to a child with Down syndrome by the age of the mother. Below are some of those statistics.

• 20-years-old: 1 in 2000
• 30-years-old: 1 in 900
• 35-years-old: 1 in 350
• 40-years-old: 1 in 100
• 45-years-old: 1 in 30
• 49-years-old: 1 in 10

There are 3 types of Down syndrome

Trisomy 21, Mosaicism and Translocation.

Trisomy 21 occurs when three copies of the twenty-first chromosome is created instead of only two. This results in the person possessing 1 extra chromosome (47 chromosomes instead of 46). According to the NDSS Trisomy 21 is the most common form of Down syndrome and accounts for 95 percent of all cases.

Mosaicism Down syndrome occurs when some of the cells within the twenty-first chromosome have three copies (like Trisomy 21) and the others have the standard two copies. The NDSS reports that this occurs in 2 percent of Down syndrome cases.

Translocation appears when there are three copies of the twenty-first chromosome, just like Trisomy 21, but one of those three chromosomes becomes attached to another chromosome, instead of staying separated. According to the NDSS this extra twenty-first chromosome can become attached to the 13, 14, 15 or 22 chromosome and accounts for 3 percent of Down syndrome cases.


Normal Chromosomes (Male)

A regular set of chromosomes (Male). Wikimedia Commons

Trisomy 21

A Trisomy 21 set of chromosomes (Male). Wikimedia Commons

4 Comments leave one →
  1. February 11, 2011 5:25 am

    I love your transitions and lucidity. I have been writing for Ghost Writers for a while now, and they pay me good to write blog posts like this, or content articles. I clear $100-$200 on a poor evening.
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  2. March 4, 2011 3:16 am

    yeah nice

  3. Danilo Saint permalink
    February 12, 2013 10:59 am

    Every year, one child in every 800 to 1,000 births will be born with a condition known as Down syndrome. Down syndrome is a disorder in which the child has extra genetic material. This extra genetic material causes the baby to develop differently in the womb. This abnormal development occurs during the early stages of cell division, soon after conception.;

    Our web portal


  1. Tweets that mention 5 Important Facts About Down Syndrome « The 21st Chromosome --

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