8

According to this 2009 ABC News article the number of children born with Down Syndrome has dropped in the USA:

In the absence of prenatal testing, the United States would have experienced a 34 percent increase in the number of Down births between 1989 and 2005, Skotko estimates.

Instead, 15 percent fewer such babies were born during that time, representing a 49 percentage point difference between expected and observed rates, according to Skotko's research.

The difference is attributed to abortions:

An estimated 92 percent of all women who receive a prenatal diagnosis of Down syndrome choose to terminate their pregnancies, according to research reviewed by Dr. Brian Skotko, a pediatric geneticist at Children's Hospital Boston.

Unfortunately, the article doesn't provide any data that would back up the claim. Has there been a study done that shows a drop in the number of Down Syndrome children being born?

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    If a trend towards later-in-life childbirth led to higher incidence of Down's Syndrome pregnancies (very strong correlation between women's age and incidence of Down's), you might not see the numbers of births reflect that in the way you'd expect. thesun.co.uk/living/1440072/… – PoloHoleSet Apr 28 '17 at 14:23
10

You may find relevant information in the paper Estimates of the live births, natural losses, and elective terminations with Down syndrome in the United States, published by Skotko along with Gert de Graff and Frank Buckley. (Which is more recent than the linked article).

The abstract of the paper includes,

As of 2007, the estimated rates at which live births with DS were reduced as a consequence of DS-related elective pregnancy terminations were 30% (95% CI: 27.3–31.9) for the U.S. as a whole.

However, the paper's data appears to show that while births with Down Syndrome are lower than they are estimated to have been without DS-related elective terminations, that in the long term they have still grown in an absolute sense.

Estimated annual live births with DS in U.S. and additional live births if no DS-related elective terminations, 1900–2010.

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    is there a simple explanation for the periodicity in that chart? – user36688 Apr 28 '17 at 14:29
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    @notstoreboughtdirt: Pure guesswork: The number of older mothers affected by wars and recent sociological trends. – Oddthinking Apr 28 '17 at 14:31
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    @notstoreboughtdirt Guess too, but the '20-'40s might be the decrease in births associated with the Great Depression. The '60s might be the 'sexual revolution' but that wouldn't really explain the subsequent increase. Though the population increase significantly after the War. census.gov/prod/2002pubs/censr-4.pdf (p. 13) that would increase the raw number (which the chart seems to show). – RomaH Apr 28 '17 at 14:39
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    These numbers following the overall birthrate is really what I was missing, the why's of the overall growth is probably too broad for comments. – user36688 Apr 28 '17 at 14:57
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    @notstoreboughtdirt The periods do seem to track the overall population birth rate trends, from here, though it is just conjecture it is logical that more total births = more births of children with Down Syndrome. – Jeff Lambert Apr 28 '17 at 15:01

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