Hospitals are not required to offer or perform autopsies. Insurers don't pay for them. Some facilities and doctors shy away from them, fearing they may reveal malpractice. The downward trend is well-known ? it's been studied for years. What has not been appreciated, pathologists and public health officials say, are the far-reaching consequences for U.S. healthcare of minuscule autopsy rates. Diagnostic errors, which studies show are common, go undiscovered, allowing physicians to practice on other patients with a false sense of security.