To read on Genome website:
Why We Screen for Down Syndrome Anyway
Even though testing is common, ethical and sociological issues remain.
By Robert Resta
Prenatal screening for Down syndrome started about 40 years ago when amniocentesis was offered to pregnant women who were 35 and older. Back then, testing the roughly 5 percent of pregnant women in the U.S. who were in this age group would have been expected to detect about 20 percent of the babies with Down syndrome. Nowadays, technological advances in screening methods have increased the potential detection rate to over 90 percent. Screening has evolved from a simple, cost-free protocol (maternal age) limited to a small niche of pregnant women into a complex and costly service that is part of care for nearly all pregnant women.
Prenatal screening also detects other chromosomal disorders besides Down syndrome but these are more like “collateral detection.” They are uncommon, and it is unlikely that widespread testing for them would be available unless it was piggybacked onto a Down syndrome screening program. Down syndrome is the engine that drives screening; other syndromes are simply passengers along for the ride (though this may change with more noninvasive prenatal testing).
One might ask: Why all the fuss about Down syndrome? While its developmental and physical effects are not negligible, people with Down syndrome can live rewarding and full lives, enriching their families and their communities with love and good citizenship. All that screening seems like a lot of effort for a disorder where, as far as I know, no one who has it was ever a serial killer, triggered an international war, committed genocide, scammed investors out of their life savings, or run a ruthless drug cartel.
In my view, the focus on Down syndrome stems from a unique confluence of factors related to the condition.
From a medical perspective, Down syndrome has the hallmarks of a condition that would justify screening. As congenital disorders go, Down syndrome is common, in part the result of the unrelenting four-decade long increase in delayed childbearing. The screening techniques for Down syndrome have a high sensitivity and a low false positive rate. Follow-up diagnostic testing is also accurate — either there is an extra 21st chromosome or there isn’t. And while the physical and cognitive effects of Down syndrome are typically not severe, they often require significant medical and other interventions. Unlike other chromosomal disorders that have a very high infant mortality rate, such as trisomy 18 and trisomy 13, the majority of babies with Down syndrome survive well into adulthood. Given the limited medical and community resources to support people with Down syndrome, and the specifics of each family’s situation, it is understandable why someone might choose to terminate a pregnancy with Down syndrome.
Psychologically, many people have deeply engrained fears of having a child with developmental problems and who looks “different.” The facial features of Down syndrome are characteristic enough that it is recognizable to someone with no medical expertise. For better or worse, from society’s standpoint, Down syndrome is often literally the face of disability.
But a more subtle reason why Down syndrome screening is widespread is that routinization begets more routinization. Offering screening to more pregnant women makes it more acceptable, resulting in the offering of screening to even more women, making it even more routine. Indeed, many of the mothers of today’s pregnant women were themselves offered screening. It is not stretching a point to say that screening is now often a given rather than an option offered.
Of course, money is the critical component that ties together all of these factors. In the 1970s, the primary justification for offering amniocentesis to women 35 and older was that it was economically cost-effective. In other words, testing for Down syndrome in a limited number of pregnant women cost less than caring for people with Down syndrome (although recent studies suggest that the costs of caring for those with Down syndrome are lower than generally assumed). Now, the biggest economic factor driving prenatal screening is that it has become a multi-billion dollar international enterprise. Labs actively sell their products to pregnancy care providers and patients. Stiff competition, patent battles, and lab buyouts and mergers all attest to the profitability of screening. There’s gold in them thar’ hills.