The ethics of abortion following prenatal screening for various disabilities or genetic diseases is contentious. Its impact is becoming clearer, however - such screening programs do significantly influence women’s decisions whether to carry pregnancies to term, and on the incidence of such conditions at birth. Cystic fibrosis is an illustrative example, in this recent article from JPeds:

JPeds, Volume 147, Issue 3, Pages 312-315 (September 2005)
Cystic Fibrosis Birth Rates in Canada: A Decreasing Trend since the Onset of Genetic Testing
Annie Dupuis, PhD, David Hamilton, PhD, David E.C. Cole, MD, PhD, Mary Corey, PhD

Abstract:
The overall CF birth rate from 1971–1987 was 1/2714 with no increasing or decreasing trend. Beginning in 1988, 1 year before identification of the CF transmembrane conductance regulator gene, estimated CF birth rates followed a linear decline to an estimated rate of 1/3608 in 2000. CF birth rates may have stabilized in the last few years, but further decline may occur with implementation of carrier screening in the general population.

In other words, the introduction of even partially-effective genetic screening for cystic fibrosis reduced the fraction of children born with that condition by 25% in 12 years. That’s a considerable impact. Its effect on the population that is born with such conditions is far-reaching and subtle. The ethics of actions with such dispersed consequences are difficult to puzzle out.

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