Down Syndrome Risk

The older a woman is when she becomes pregnant, the greater the Down syndrome risk. Parents who already have a child with the condition have a 1 percent chance that another child with the disorder will be born, regardless of maternal age. If one of the parents is a balanced translocation carrier (part of chromosome 21 is attached to another chromosome), that may increase the Down syndrome risk.

 

Down Syndrome Risk: An Introduction

There are several established Down syndrome risk factors, including:
 
  • A previous Down syndrome baby
  • Increasing maternal age
  • Carriers of a balanced translocation.
     

Down Syndrome Risk: A Previous Down Syndrome Baby

For parents of children with Down syndrome, there is about a 1 percent chance that another Down syndrome child will be born in a subsequent pregnancy, regardless of maternal age.
 

What's the Down Syndrome Risk by Age?

The likelihood that a woman under 30 who becomes pregnant will have a baby with Down syndrome is less than 1 in 1,000, but the chance of having a baby with Down syndrome increases to 1 in 400 for women who become pregnant at age 35. The likelihood of Down syndrome continues to increase as a woman ages, so that by age 42, the chance is 1 in 60 that a pregnant woman will have a baby with Down syndrome, and by age 49, the chance is 1 in 12.
 
The Down syndrome risk by age is broken out in the following table.
 
Mother's Age
Incidence of Down Syndrome
Under 30
Less than 1 in 1,000
30
1 in 900
35
1 in 400
36
1 in 300
37
1 in 230
38
1 in 180
39
1 in 135
40
1 in 105
42
1 in 60
44
1 in 35
46
1 in 20
48
1 in 16
49
1 in 12
 
Many specialists recommend that women who become pregnant at age 35 or older undergo prenatal screening and/or testing for Down syndrome.
 
(Click Prenatal Screening for Down Syndrome for more information.)
 
(Down Syndrome Risk Continued: Page 2)
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Written by/reviewed by: Arthur Schoenstadt, MD
Last reviewed by: Arthur Schoenstadt, MD