maternal age and chance of Down's syndrome

Last edited 05/2023 and last reviewed 05/2023

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 1:16000.067
45 and over1.50 and greater2.0

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.

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