risk of Down's in relation to maternal age

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

The levels of risk 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)

Risk as a ratio%Risk
Below 20 1:16000.067
45 and over1.50 and greater2.0

If the mother of an affected child is under 36 then the risk 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 www.screening.nhs.uk/an

Last reviewed 04/2021