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Age of mother and chance of Down's syndrome

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The chance of having a baby with Down's syndrome is related to the age of the mother, approximately as follows:-

The levels of chance associated with having a Down's syndrome pregnancy in relation to a woman's age are shown in the table below:

 

Woman's age (years)

Chance as a ratio

%Chance

Below 20

1:1600

0.067

20

1:1500

0.066

30

1:800

0.125

35

1:270

0.37

40

1:100

1.0

45 and over

1.50 and greater

2.0

If the mother of an affected child is under 36 then the chance of a further child being affected is said to be about 1 in 100.

Note however that the absolute numbers of mothers having children with Down's syndrome is greater in the younger age groups; this is because the total number of mothers in these groups is much higher.

For more information then see https://view-health-screening-recommendations.service.gov.uk/downs-syndrome/


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