Dr. Erin Tracy of Massachusetts General Hospital in Boston warns that such genetic testing is poorly regulated and may present potential pitfalls for patients and physicians.

"Some of the tests that are being offered have no proven clinical validity whatsoever and are quite costly," Tracy said in a statement. "So patients spend money trying to identify a particular gene to figure out if their child is prone to addictive behavior, for example. If the test comes back positive, parents are often not adequately counseled as to what those results might mean, whether these tests have any proven value, or what resources are available for follow up."

Results of genetic tests have the potential to cause excessive alarm or to assure consumers falsely that they will not develop cancer or other diseases -- and direct-to-consumer advertising for genetic tests may give the erroneous impression that a certain test is mandatory, Tracy said.

Patients should consult their physicians about cancer risk, he said, and before any test is ordered thought should be given as to whether a particular test is appropriate.

The findings are published in Obstetrics & Gynecology.