If parents discover that they both carry risk variants for the same disease, they can choose to undergo in vitro fertilization and have embryos screened for the disease prior to being implanted in the womb. Or the woman can choose to get pregnant the normal way and then they can have the fetus screened during pregnancy.

Testing is likely to lead to an increase in techniques such as in vitro fertilization and preimplantation genetic diagnosis, which together cost about $12,000 to $17,000. But that figure is still drastically lower than the hundreds of thousands to millions of dollars it can cost to take care of a child with a severe genetic disorder. "That's why we got insurance coverage so rapidly, which is extremely unusual for a new diagnostic test," says Balaji S. Srinivasan, chief technology officer at Counsyl.

In addition to getting the test through fertility clinics, consumers can order it directly through the Internet, similar to services provided by startups 23andMe, Navigenics, and DecodeMe. While these companies have largely pioneered the concept of direct-to-consumer genetic testing--and garnered extensive media attention doing so--their goal is much different than Counsyl's. Their screens are designed to detect common genetic variants that have a fairly minor impact on an individual's risk for a number of common diseases, while Counsyl's test detects rare genetic variants linked to serious diseases in people carrying two copies of it.

Reilly predicts other companies will soon follow suit. "I think there will be lots of other groups offering similar tests in the future," he says. "There's no reason why 23andme couldn't do this, or Navigenics or Baylor or the Mayo clinic."

Counsyl uses a technology called a molecular inversion probe array, which can capture small, select pieces of DNA and allow them to be analyzed with high accuracy. Srinivasan says the company will publish details of the method as well as its accuracy in a peer-reviewed journal this week. He says the company also plans to change its screening methods in the near future, using gene sequencing technology, which determines every letter of the selected genes.

The test is not foolproof. It doesn't detect a number of genetic and environmental factors that can affect a healthy pregnancy. In addition, many of the mutations underlying the conditions encompassed by the test have not yet been discovered, meaning someone may still be a carrier.