The U.S. Food and Drug Administration has tightened the rules guiding the use of vaginal mesh implants for the treatment of pelvic organ prolapse in women. The new rules are in response to thousands of injuries reported with the problem-prone device.

The devices were reclassified on Monday from a “moderate” to “high” risk category. Manufacturers must now submit pre-market approval applications to the FDA to help the agency better assess the implants’ safety and effectiveness.

The new requirements do not apply to mesh products when used to treat other conditions such as hernias or urinary incontinence. The FDA action comes more than four years after the agency concluded that women getting vaginal mesh have more complications than women who undergo traditional surgery with stitches. Mesh products were introduced for pelvic repair in the 1990s and promoted as a way to speed patients’ recovery time. But FDA advisers said those benefits have not been established.

Makers of transvaginal mesh implants already on the market now have 30 months to submit pre-market approval applications, while makers of new devices must submit an application before they can be approved for sale in the United States, the FDA said.

Patients have filed tens of thousands of lawsuits against mesh manufacturers, including Johnson & Johnson, Boston Scientific and Endo International. In 2014, Ireland-based Endo said it would pay $830 million to settle more than 20,000 personal injury lawsuits.