What are the risk factors for Down syndrome?

Risk factors for Down syndrome include: Advancing maternal age; being carriers of the genetic translocation for Down syndrome, and having had one child with Down syndrome. For most women, your Down syndrome risk is based mostly on the mother's age. This calculator will let you know your own personalized risk based on your age.


What is Down syndrome?

Down syndrome is a genetic disorder caused by a duplication chromosome. Patients with Down syndrome have two copies of chromosome 21 so they are born with 47 chromosomes as opposed to the normal 46. Another name for the condition is Trisomy 21. 

Who is at Risk for Down syndrome?

Advanced maternal age is a risk factor for Down syndrome. Maternal age over of 35 at time of pregnancy increases risk of having a child with Down syndrome to one in 400. That risk jumps to one in 35 for women over 45.  

Despite the increased risk to women over 35, women under the age of 35 give birth to more children with Down syndrome than older women. Statistically the increased number of Down syndrome cases is associated with the number of overall births to women under 35 – more births equates to more children born with the syndrome. Women who have given birth to a child with Down syndrome are at increased risk of having a second or subsequent child with the condition. 

Symptoms of Down syndrome

The duplicate chromosome 21 causes physical and mental abnormalities of varying severity. Physical abnormalities may affect the head, eyes, neck, and fingers.

Children with Down syndrome tend to have flat facial features, upward slanted eyes (not related to ethnicity), short neck and fingers and smaller than average head size. Patients may also develop poor muscle tone. 

Physical and mental development may be slower than peers or stunted. Mental and social delays are typically present – though in varying degrees. Delays may manifest as:

  • Slower learning
  • Agitation
  • Shortened attention span

Diagnosis of Down syndrome

Physical abnormalities may affect physical development of internal organs, including the brain, eyes, heart and other organs. Down syndrome may increase the likelihood of:

  • Heart-related birth defects
  • Dementia
  • Vision problems
  • Gastrointestinal blockage
  • Joint problems
  • Chronic constipation
  • Hypothyroidism

Treatment of Down syndrome

There is no treatment or cure for Down syndrome. Patient health issues are treated on a case-by-case basis. Patients with some organ deformities, including heart defects or gastrointestinal blockage may require surgery. 

Down Syndrome and Pregnancy

Down syndrome in females does not typically affect ability to get pregnant, stay pregnant or give birth to a normal, healthy baby. Women with Down syndrome may be at increased risk of sexual abuse. 

Life Expectancy of Down syndrome

Patients with Down syndrome can live long, productive lives with proper medical care, special education and life training. Medical attention may be required for life due to potential for physical abnormalities and conditions.

Why is it called "Down Syndrome"

Down syndrome is named after John Langdon Down, the British doctor who described it in 1866. The extra genetic material causes delays in the way a child develops, and often leads to mental retardation. In general, symptoms of Down syndrome can vary widely from child to child. While some kids with Down syndrome need a lot of medical attention, others lead very healthy and independent lives.

Normally, at the time of conception a baby inherits genetic information from its parents in the form of 46 chromosomes: 23 from the mother and 23 from the father. In most cases of Down syndrome, however, a child gets an extra chromosome — for a total of 47 chromosomes instead of 46. It's this extra genetic material that causes the physical and cognitive delays associated with Down syndrome.

Although no one knows for sure why Down syndrome occurs and there's no way to prevent the chromosomal error that causes it, scientists do know that as women get older they have a significantly higher risk of having a child with the condition. Down syndrome affects about 1 in every 800 babies born, with a lower risk in younger women and a higher risk in older women. At age 30, for example, a woman has less than a 1 in 1,000 chance of conceiving a child with Down syndrome. Those odds increase to 1 in 400 by age 35. By 42, it jumps to about 1 in 60.

Risk table from: From Hook EB. JAMA 249: 2034-2038, 1983