Embryo screening can decrease disease risk, but it's controversial. (Image credit: Sandy Huffaker/Bloomberg/Getty Images)

Breast cancer is the latest disease being bred out of families through preimplantation genetic diagnosis - an embryo screening test once reserved for fatal genetic disorders.

The test, dubbed PGD, uses a single cell to scour the DNA for genetic typos during the in vitro fertilization process. Embryos with disease-causing mutations are then discarded in favor of their genetically superior siblings.

Learn more about embryo screening.

PGD has long been used to prevent hereditary disorders like Huntington's disease and cystic fibrosis. And while certain gene mutations raise the risk of breast cancer, some experts say screening embryos pushes ethical boundaries.

"I think it's ethically much, much more controversial," said Art Caplan, professor of bioethics at NYU Langone Medical Center. "We've moved from testing for a disease that's going to affect a person with certainty to testing for a risk factor that may or may not affect them."

Women with mutations in the genes BRCA1 or BRCA2 are five times more likely to be diagnosed with breast cancer, according to the National Cancer Institute. That means that 60 percent of women with a BRCA mutation will develop breast cancer in their lifetime, compared to 12 percent of women in the general population.

Should you get BRCA gene testing?

But not everyone with a BRCA mutation develops breast cancer, and many women without BRCA mutations do.

"At some point everyone has health risks," said Caplan. "As much as people don't like to admit it, a genetic test is one that no one can pass."

Caplan said PGD raises the possibility of "designer babies" - spawn selected for traits unrelated to health.

"We're talking about disease risk today, but it could become a better, improved, more perfect baby tomorrow," he said.

Some couples already use PGD to stack the odds of having a boy or girl - a controversial and expensive practice allowed here in the U.S. but banned abroad.

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