Maternal Age Effect (see also Down syndrome)

There is an increased risk of chromosome anomalies with advancing maternal age. The observed risk of having a live born baby with Down syndrome (in the absence of a family history) is:

Age         Risk

25        1 in 1500

30        1 in 800

35        1 in 350

36        1 in 300

37        1 in 200

38        1 in 170

39        1 in 140

40        1 in 100

45        1 in 30

Accurate prenatal diagnosis by chorionic villus sampling (CVS) or amniocentesis is available.

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