Dr Jozef Gecz, from the hospital's Department of Cytogenetics and Molecular Genetics, led the research.

BBC: Epilepsy 'master gene' found

Though companies say patients should confirm positive results with invasive procedures, such case studies show "that message isn't driven home enough, " said Athena Cherry, director of Stanford University Medical Center's cytogenetics laboratory.

WSJ: New Questions on Cutting-Edge Prenatal Tests