A California doctor faces up to 20 years in prison after he admitted to defrauding patients and their insurers by implanting and billing for unapproved intrauterine devices (IUDs), the U.S. Attorney's Office recently announced.

Paul S. Singh, MD, an obstetrician-gynecologist from Tehachapi, Calif., pleaded guilty to mail fraud this week for a scheme that involved him purchasing cheap, unapproved IUDs off of the internet and using them in unknowing patients.

Between 2008 and 2012, Dr. Singh would purchase copper IUDs that had not been approved by the FDA online for a low price. Then, without patients' consent, he would implant the devices and bill insurers for more expensive, FDA-approved devices instead.

During the time he was using the devices, the FDA repeatedly warned doctors across the country about the risks of using unapproved IUDs and told them not to use them. Dr. Singh ignored these warnings, the government says. He was eventually confronted by the FDA in 2010 and promised to stop using the IUDs in patients. However, he allegedly continued the scheme for another 2 years until federal agents searched his office and found they were still in use.

The devices left several of Dr. Singh's patients with complications — including pain and sexual and reproductive problems — the government says. When patients returned to Dr. Singh with complaints about the device, he would re-insert a new, unapproved device instead of removing the IUD. Patients ultimately had to switch doctors to have the devices removed.

"Medical doctors have a special responsibility to make the best choices for their patients," says Lisa L. Malinowski, special agent in charge with the FDA Office of Criminal Investigations, in a statement. "When they ignore that responsibility and use unapproved medical devices, they put patients' safety and health at risk."

Dr. Singh pleaded guilty to mail fraud on Aug. 24 and is scheduled for sentencing at the end of November. He faces a maximum statutory sentence of 20 years in prison and a $250,000 fine.

Kendal Gapinski