The use of preimplantation genetic diagnosis, the powerful technique employed during fertility treatment to select embryos based on their genes, is currently unregulated in the United States—unlike in nearly all other countries where PGD is available. Of course, the analytical quality of the genetic tests, the laboratories where they are performed, and the technicians who carry them out are subject to the Clinical Laboratory Improvement Amendment requirements. And as the Food and Drug Administration prepares to begin regulating laboratory-developed tests, including many genetic tests, the clinical validity of the tests may also need to be demonstrated. But neither CLIA nor the U.S. Food and Drug Administration is responsible for governing medical practice, and state law and the relevant medical associations have largely fallen silent on the questions of when and why PGD ought to be performed. The result of this regulatory lacuna is that while PGD was originally intended for screening embryos for severe heritable disorders, it is now also employed for a variety of more controversial purposes.