Incidence of Down Syndrome with Increasing Maternal Age

What is your risk for having a baby with Down Syndrome given your age?

Mother getting prenatal care
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Down Syndrome is a genetic disorder that means your baby has one extra chromosome, 47 instead of 46. It is typically diagnosed either prenatally, through various tests, or after birth, usually first suspected because of visual signs and confirmed by genetic testing.

If you are receiving prenatal care, you will likely be offered genetic screening. It is recommended that all mothers are offered genetic testing, so do not be concerned if your practitioner mentions this testing.

Genetic screenings are typically done with maternal blood or ultrasound or a combination of both. Ultrasound testing is called nuchal fold translucency testing. One of the most common lab tests available is the AFP blood testing. If either of these tests are positive or indicate an increased risk of risk, you may be offered or decide to do a genetic test called an amniocentesis or chorionic villus sampling (CVS) which can provide a definitive diagnosis of Down Syndrome. There are also other tests available.

One of the major factors that can influence if your baby has Down Syndrome or another trisomy is the age of the mother. We know that as the age of the mother at the time of birth goes up, so does the risk of her baby being born with a genetic defect, like a trisomy. Here is a list showing you what your chances are for a baby being born with Down Syndrome versus all trisomies.

Your doctor or midwife may advise that you have genetic testing depending on a variety of factors.

Age is merely one of these factors. When in doubt, you can always request a referral for genetic counseling. This can give you a more complete look at your risk factors that take into account, not only your age, but your familial history.

The chart is below.

Mothers Age    Risk for Down Syndrome    Risk for All Trisomies
201 in 1,6671 in 526
211 in 1,4291 in 526
221 in 1,4291 in 500
231 in 1,4291 in 500
241 in 1,2501 in 476
251 in 1,2501 in 476
261 in 1,1761 in 476
271 in 1,1111 in 455
281 in 1,0531 in 435
291 in 1,0001 in 417
301 in 9521 in 384
311 in 9091 in 384
321 in 7691 in 323
331 in 6251 in 286
341 in 5001 in 238
351 in 3851 in 192
361 in 2941 in 156
371 in 2271 in 127
381 in 1751 in 102
391 in 1371 in 83
401 in 1061 in 66
411 in 821 in 53
421 in 641 in 42
431 in 501 in 33
441 in 381 in 26
451 in 301 in 21
461 in 231 in 16
471 in 181 in 13
481 in 141 in 10
491 in 111 in 8



Gabbe, S, Niebyl, J, Simpson, JL. Sixth Edition. 2012.

Estimating a woman's risk of having a pregnancy associated with Down's syndrome using her age and serum alpha-fetoprotein level (pages 387–402) H. S. CUCKLE, N. J. WALD and S. G. THOMPSON Article first published online: 22 AUG 2005 | DOI: 10.1111/j.1471-0528.1987.tb03115.x

OB/GYN Secrets, 2nd Edition. Frederickson,HL & Wilkins-Haug, L. 1997.

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