given our society's track record with prenatal testing for Down syndrome, we also have a pretty good idea of what individuals and couples will do with comprehensive information about their unborn child's potential prospects. In 90 percent of cases, a positive test for Down syndrome leads to an abortion. It is hard to imagine that more expansive knowledge won't lead to similar forms of prenatal selection on an ever-more-significant scale.
The number gets thrown about all the time: 90% of babies with a prenatal diagnosis of Down syndrome are aborted. Often it's reported in shorthand, 90% of babies with Down syndrome are aborted. The latter statement is patently untrue. The former is somewhat inaccurate. And these numbers matter.
To explain the patently untrue part: Many women self-select out of a prenatal diagnosis, whether because they would not abort a baby with an identified genetic abnormality, or because their chance (based either upon age or prenatal screening tests) of having a baby with a genetic abnormality is low, or for some other reason. Only 2-3% of all pregnant women choose CVS or amniocentesis, the current definitive tests for chromosomal abnormalities, including Down syndrome. When you plot out the number of women who we would expect (based upon population studies and maternal age) to be having a child with Down syndrome versus the number of babies who are born with Down syndrome every year, we can conclude that 50% of babies conceived with Down syndrome are aborted. Presumably most of those abortions are based upon information gained via prenatal testing. (Prenatal Diagnosis, February, 2011, James Egan, et al.)
To explain the somewhat inaccurate part: Of the 2-3% of women who receive a definitive diagnosis that their baby has Down syndrome, some studies have demonstrated that approximately 90% of those women chose abortion. Those numbers usually come from single studies that indeed demonstrate an abortion rate around 90%. But a review of all the available studies from 1995-2011 in the United States of women with a prenatal diagnosis of Down syndrome (by Jamie Natali, et. al., in Prenatal Diagnosis, 2012, 142-153), demonstrates:
The weighted mean termination rate was 67% (range: 61%–93%) among seven population-based studies, 85% (range: 60%–90%) among nine hospital-based studies, and 50% (range: 0%–100%) among eight anomaly-based studies. Evidence suggests that termination rates have decreased in recent years. Termination rates also varied with maternal age, gestational age, and maternal race/ethnicity.
This systematic review presents the largest synthesis of United States data on termination rates following a prenatal diagnosis of Down syndrome. Evidence suggests that termination rates are lower than noted in a previous review that was based on less contemporary studies and had an international focus. Heterogeneity across studies suggests that a summary termination rate may not be applicable to the entire US population.
To explain why these numbers matter: In other words, there are thousands of babies with Down syndrome who are aborted every year based upon prenatal diagnoses. And there are thousands who aren't. As I wrote when I first learned the complexities of this data (90% of Babies with Down syndrome Aborted, Really?):
The reason I'm drawing attention to the fact that so many children with Down syndrome are not aborted is that I want women who opt out of prenatal testing or who choose to continue a pregnancy with a prenatal diagnosis or who give birth unexpectedly to a child with Down syndrome–I want these women to know that they are not alone. Thousands of other parents are in your shoes. Thousands of other families have made similar choices. And hundreds of thousands of individuals can testify to the goodness and purpose in the lives of their friends and family members with Down syndrome.
Ross Douthat, Bristol Palin and countless others are certainly right when they decry the number of babies with Down syndrome who are aborted every year as a result of prenatal testing. And Douthat offers a good and important analysis of the grave problems with human hubris in thinking that we should try to engineer human beings according to our ideals of achievement, mastery, and success. But the data demonstrates that many families are still choosing life for babies with Down syndrome. Providing accurate numbers when women with a prenatal diagnosis face the decision about whether to terminate might just save some lives.
I'm currently working on an ebook with Patheos about prenatal testing that will come out this fall.