What Are the Risks Based on My Age?

To the Point- the chance of your baby having a trisomy, for example, Down syndrome, gradually increases with age and the increase is more dramatic after age 35, however, moms of all ages can have babies with trisomies.

AgeChance of Down SyndromeChance of All Trisomies
201/1667 (0.06%)1/526 (0.19%)
251/1250 (0.08%)1/476 (0.21%)
301/952 (0.11%)1/385 (0.26%)
351/385 (0.26%)1/202 (0.5%)
361/295 (0.34%)1/162 (0.62%)
371/227 (0.44%)1/129 (0.78%)
381/175 (0.57%)1/102 (0.98%)
391/137 (0.73%)1/82 (1.22%)
401/106 (0.94%)1/65 (1.54%)
411/82 (1.22%)1/51 (1.96%)
421/64 (1.56%)1/40 (2.5%)
431/50 (2%) 1/32 (3.13%)
441/38 (2.63%) 1/25 (4%)
451/30 (3.33%)1/20 (5%)
461/23 (4.35%)1/16 (6.25%)
471/18 (5.56%) 1/13 (7.69%)
481/14 (7.14%)1/10 (10%)
491/11 (9.09%)1/7 (14.29%)

Age is based on age at expected time of delivery. Data have been modified from Hook et al. 1

As you can see from the table above, the chance of one of these chromosome abnormalities occurring in baby gradually increases as mom’s age increases. BUT, nothing crazy happens when you turn 35!

Of note, we have included fraction risks and percentage risks. Sometimes the fraction version of the number sounds higher to people than the percentage, which is why we have included both.

 

1.  Hook EB, Cross PK, Schreinemachers DM. Chromosomal abnormality rates at amniocentesis and in live-born infants. JAMA 1983;249(15):2034-38.


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