According to the Centers for Disease Control and Prevention, approximately 6,000 babies are born in the United States each year with Down syndrome, or approximately 1 out of every 691 live births.1
Down syndrome is the most frequent chromosomal cause of mild to moderate intellectual disability, and it occurs in all ethnic and economic groups. Currently, more than 400,000 people are living with Down syndrome in the United States, according to the National Down Syndrome Society.2
Researchers know some, but not all, of the risk factors for Down syndrome. For example, parents who have a child with Down syndrome or another chromosomal disorder, or who have a chromosomal disorder themselves, are more likely to have a child with Down syndrome.3
In the United States, demographic factors also affect the risk for a child to be born with Down syndrome. These factors include geographic region, maternal education, marital status, and Hispanic ethnicity.4,5
Maternal Age and Risk for Down Syndrome
Because the likelihood that an egg will contain an extra copy of chromosome 21 increases significantly as a woman ages, older women are much more likely than younger women to give birth to an infant with Down syndrome. Although women older than 35 years of age make up less than 15% of all births6 in the United States each year, about 40% of babies with Down syndrome are born to women in this age group.4
This likelihood increases as age increases. Following are the rates of Down syndrome for select ages:4,5,7,8
- At age 25, the likelihood is 1 in 1,300
- At age 30, the likelihood is 1 in 900
- At age 35, the likelihood is 1 in 350
- At age 42, the likelihood is 1 in 55
- At age 49, the likelihood is 1 in 25
World Down syndrome day. Retrieved June 11, 2012, from
Down syndrome fact sheet. Retrieved June 11, 2012, from
Davidson, M. A. (2008). Primary care for children and adolescents with Down syndrome.
Pediatric Clinics of North America, 55, 1099–1111.
Egan, J. F., Smith, K., Timms, D., Bolnick, J. M., Campbell, W. A., & Benn, P.A. (2011). Demographic differences in Down syndrome livebirths in the U.S. from 1989 to 2006.
Prenatal Diagnosis, 31, 389–394.
Parker, S. E., Mai, C. T., Canfield, M. A., Rickard, R., Wang, Y., Meyer, R. E., et al. (2010). Updated national birth prevalence estimates for selected birth defects in the United States, 2004–2006. Birth Defects Research. Part A, Clinical and
Molecular Teratology, 88, 1008–1016.
Livingston, G. & Cohn, D. (2010).
The new demography of American motherhood. Pew Research Center. Retrieved July 23, 2011, from
NDSS. (n.d.). Incidences and maternal age. Retrieved June 11, 2012, from
Morris, J. K., Wald, N. J., Mutton, D. E., & Alberman, E. (2003). Comparison of models of maternal age-specific risk for Down syndrome live births.
Prenatal Diagnosis, 23, 252–258.