A couple in Britain recently successfully screened out a genetic predisposition for breast cancer from the child the woman is now pregnant with:

Doctors screened out from the woman’s embryos an inherited gene that would have left the baby with a greater than 50% chance of developing the cancer.

The woman decided to have her embryos screened because her husband had tested positive for the gene and his sister, mother, grandmother and cousin have all had the cancer.

But the "brave new world" solution to the fear of having a child that may some day become sick comes at a steep price: the lives of every other embryo that might have eventually gotten sick with the disease (and several "extras" that wouldn't have). Seven of the eleven embryos created by the in-vitro fertilization were destroyed.

The screening process, known as pre-implantation diagnosis, could be used for a variety of genetic defects, promising to stop the objectionable hereditary line in couples carrying the problematic genes.

But the door such a possibility opens could well lead into a darkness we have not yet considered. Even those who find nothing morally disturbing about parents choosing to do such a thing should pause for a moment to consider what such a technique could become in the hands of governments bent on reducing health care costs, or in those whose "disapproved" genes run not just to actual diseases, but to tendencies, ethnicities, or sexual orientation.

The last time the world saw a systematic attempt at eugenics, it was cut short in its first generation, and seems to have had no positive effects and the most horrific negative ones. When young blonde women in Germany and other nations overrun by the Third Reich were impregnated by German soldiers to create a "master race," in the lebensborn program, it did not lead to a marvelous new order, but merely tore apart families and ruined the lives of everyone it touched. While the program bred the master race only by determining which pregnant women would give birth and be nurtured and which would not, it is chilling to imagine what they could have done with a systematic program designed to breed only those guaranteed to be perfect specimens.

Will the same Western nations that defeated the racist ideology that bred humans like cattle now, little more than a mere half-century later, use the same heartless calculus in attempting to bring about a disease-free society?

It may be too much to hope that eventually we mere mortals will learn not to play God. But while we are playing, it would be wise to take account of the minefield we are playing in.