logo

Trisomies

Trisomy 21

Trisomy 21 (Down syndrome)

  • Is caused by the presence of an extra
    chromosome
    in the 21st pair in the cells. A person with trisomy 21 therefore has 47 chromosomes instead of 46.
  • Is the most common chromosomal abnormality where the foetus is viable.

  • Affects about one in 800 births.

  • Can cause health problems (e.g. heart or bowel defects, vision or hearing problems, epilepsy, etc.).

    • People with Down syndrome may:

  • Need a certain degree of support throughout their lives (most of them).
  • Hold a job and lead an almost independent life (some of them).
  • Develop meaningful emotional relationships and lead rewarding lives (most of them).

    • Life expectancy

  • Aging is faster than average for people affected with trisomy 21.
  • Alzheimer disease is 3 to 5 times more frequent for people affected with trisomy 21 (25% at 35 years old) than for the general population (5% at 65 years old).
  • The average life expectancy is 60 years old.

Trisomy 18

Trisomy 18 (Edwards syndrome)

  • Is caused by the presence of an extra
    chromosome
    in the 18th pair in the cells.

  • Affects about 1 in 4,500 births

  • People with Edwards syndrome may have severe malformations and/or stunted growth during pregnancy or after birth.

    • Life expectancy

  • More than 95% of pregnancies end in miscarriage.
  • Most babies born with trisomy 18 will die within the first year of life. About 5% to 10% live beyond one year.

Trisomy 13

Trisomy 13 (Patau syndrome)

  • Is caused by the presence of an extra
    chromosome
    in the 13th pair in the cells.

  • Affects about 1 in 7,000 births.

  • Often associated with multiple malformations.

    • Life expectancy

  • More than 95% of pregnancies end in miscarriage.
  • Most babies born with trisomy 13 will die within the first year of life. Fewer than 10% live beyond one year.

General probability of trisomies 21, 18 and 13

The circle on the left shows the general probability that a pregnant woman will carry a child with a trisomy in a sample of 10,000 women. As for the circle on the right, it takes the probability in the circle on the left, but divides it into three groups: trisomy 21, trisomy 18 and trisomy 13.

Number estimation for all 3 trisomies out of 10 000 pregnant women

16 9984 10 000

Number estimation for each type of trisomies out of 10 000 pregnant women

13 2 1 16

No case of trisomy

Total

Cases of trisomy 21

Cases of trisomy 18

Cases of trisomy 13

Out of 10,000 pregnant women...

On average, 13 carry a baby with trisomy 21, 2 carry a baby with trisomy 18 and 1 carries a baby with trisomy 13.

Your risk of trisomies 21, 18 and 13 according to your age.

A number of factors can influence the development of trisomy. However, the main factor is the mother's age. The older the mother, the higher the probability.

Probability according to the mother's age

Click on your age in the horizontal bar to find out your
probability
of having a child with a
trisomy
. According to the age you have indicated, the circle on the left presents the probability that you will have a child with trisomy on a sample of 10,000 women of the same age as you. The circle on the right takes the probability obtained in the circle on the left, but divides it into three groups: trisomy 21, trisomy 18, and trisomy 13.
30

Number estimation for all 3 trisomies out of 10 000 pregnant women

18 9982 10 000

Number estimation for each type of trisomies out of 10 000 pregnant women

10 6 2 18

No case of trisomy

Total

Cases of trisomy 21

Cases of trisomy 18

Cases of trisomy 13

Out of 10,000 pregnant women...

At 30 years old, 10 carry a baby with trisomy 21, 6 carry a baby with trisomy 18 and 2 carry a baby with trisomy 13.