Zeev's Turnips Talk Politics (ZTTP)

[nwsun]

look at the incidence section... it has some numbers that imply most downs syndrome births are to woman 35 and under...

http://en.wikipedia.org/wiki/Down_syndrome

Incidence

Graph showing increased chance of Down syndrome compared to maternal age.The incidence of Down syndrome is estimated at one per 800 to one per 1000 births.[12] In 2006, the Center for Disease Control estimated the rate as one per 733 live births in the United States (5429 new cases per year).[13] Approximately 95% of these are trisomy 21. Down syndrome occurs in all ethnic groups and among all economic classes.

Maternal age influences the chances of conceiving a baby with Down syndrome. At maternal age 20 to 24, the probability is one in 1562; at age 35 to 39 the probability is one in 214, and above age 45 the probability is one in 19.[14] Although the probability increases with maternal age, 80% of children with Down syndrome are born to women under the age of 35,[15] reflecting the overall fertility of that age group. Recent data also suggest that paternal age, especially beyond 42,[16] also increases the risk of Down Syndrome manifesting in pregnancies in older mothers.[17]

Current research (as of 2008) has shown that Down syndrome is due to a random event during the formation of sex cells or pregnancy. There has been no evidence that it is due to parental behavior or environmental factors.